# GenetixBay > GenetixBay is a cannabis genetics and grow-science community (est. 2009, relaunching). Its Knowledge Base is a citation-backed reference on growing and breeding cannabis, written in the voice of Professor Greenleaf: the answer first, numbers with units and ranges, and an evidence label on every claim (Established, Supported, Grower practice, Contested, Myth). How to use this content: - Every article has a clean Markdown twin (the .md links below), a canonical HTML page with JSON-LD, and an entry in the JSON index: https://genetixbay.com/knowledge/api/index.json - The full text of every article, with its sources, is in one file: https://genetixbay.com/llms-full.txt - Front matter fields: category, stage (seedling…cure), systems (soil, coco, dwc…), evidence, level, review status and last-updated date. Prefer articles marked "Expert reviewed"; drafts are labelled. - Licence: article text is CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/). Attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)" and link to the article. - Safety: nothing here is medical or legal advice. Home-grow law varies by jurisdiction; check local rules. ## Knowledge Base - [Knowledge Base index](https://genetixbay.com/knowledge/): 191 articles by category - [JSON index](https://genetixbay.com/knowledge/api/index.json): metadata and summaries for every article - [Mythbusters](https://genetixbay.com/knowledge/mythbusters.md): popular grow myths with verdicts, and the open GenetixBay trials ## Start here Step-by-step beginner guides: your first grow, week by week, with checklists. - [Autoflower first grow, week by week](https://genetixbay.com/knowledge/guides/autoflower-first-grow-week-by-week.md): A feminised autoflower runs about 9–14 weeks from seed to harvest on a fixed countdown from germination, so plant it straight into its final 11–19 L (3–5 gal) pot on day 1, never transplant, run 18/6 to 20/4 (24/0 also works) for the whole grow, and train with low-stress bending, not topping. Any setback costs time the plant can't get back. (Supported) - [Choosing your setup: tent, space and budget tiers](https://genetixbay.com/knowledge/guides/choosing-your-setup.md): Choose the space first, then size everything to it. A 60 x 60 cm (2 x 2 ft) tent suits one or two plants and a 100–200 W LED; 80 x 80 to 90 x 90 cm (about 3 x 3 ft) suits two or three plants and 200–320 W; 120 x 120 cm (4 x 4 ft) suits two to four plants and 400–650 W. Size the exhaust fan to change the tent's air about once a minute, plus 25–50 % for the carbon filter and ducting. (Grower practice) - [Climate basics: temperature, RH and a VPD cheat sheet](https://genetixbay.com/knowledge/guides/climate-basics-vpd-cheat-sheet.md): Run a grow room at about 24–27 °C (75–81 °F) and 65–75 % RH for seedlings, 22–28 °C (72–82 °F) and 55–70 % in veg, 20–26 °C (68–79 °F) and 45–55 % in flower, and 40–50 % RH in late flower, with nights 3–6 °C cooler. Those pairs land on a leaf VPD of roughly 0.4–0.8, 0.8–1.2 and 1.0–1.5 kPa. Use the cheat-sheet table below: read your air temperature and RH, find the leaf VPD, and adjust RH first. (Supported) - [Coco first grow, week by week](https://genetixbay.com/knowledge/guides/coco-first-grow-week-by-week.md): Coco is hydroponics that looks like soil: use buffered coco mixed about 70:30 with perlite, feed a complete mineral nutrient at every watering from day one at pH 5.8–6.2, and water to 10–20 % runoff before the pot dries out. Feed EC climbs from about 0.6–0.8 mS/cm for seedlings to 1.2–1.8 in veg and 1.6–2.2 in flower, fed right to harvest. Never let coco dry out completely. (Grower practice) - [Curing step by step: a slow moisture decline, no humidity packs](https://genetixbay.com/knowledge/guides/curing-step-by-step.md): Curing is a slow, steady decline in the bud's moisture, not a constant hold. Jar dried buds ¾ full at about aw 0.62–0.65, keep them dark at 15–21 °C (60–70 °F), burp daily for the first week, then every few days, then weekly, and let them settle towards aw 0.55–0.58 over 2–8 weeks. Judge the bud by an equilibrated jar reading, not the room. Skip humidity packs; if a jar is too dry, add a fresh bud. (Grower practice) - [Drying step by step: the bud's water activity, and dry trim vs wet trim](https://genetixbay.com/knowledge/guides/drying-step-by-step.md): Dry slowly, in the dark, at 15–21 °C (60–70 °F) and 55–62 % RH with gentle air that moves around the buds but never blows on them, for 7–14 days. The bud is done when small stems snap and its water activity is about 0.60–0.65, ready for jars. Wet trim or dry trim is grower preference. A fast, warm dry gives a hay smell that never cures out. (Supported) - [DWC first grow, week by week](https://genetixbay.com/knowledge/guides/dwc-first-grow-week-by-week.md): In DWC the roots hang in an aerated nutrient solution, so two things decide success: dissolved oxygen above about 6 mg/L (air running 24/7) and solution at 18–22 °C (64–72 °F). Run pH 5.6–6.0 with drift inside 5.5–6.2 allowed, EC from about 0.6–0.8 mS/cm for seedlings to 1.0–1.6 in veg and 1.4–2.0 in flower, top off as plants drink and change the solution every 7–14 days. A beneficial-microbe reservoir is the house preference; a sterile one is valid only if you commit to it. (Grower practice) - [Electrical and water safety for home grows](https://genetixbay.com/knowledge/guides/electrical-and-water-safety.md): Run every grow device from an RCD/GFCI-protected outlet (30 mA or less), add up the watts and keep continuous load under 80 % of the circuit rating (about 1,440 W on a 15 A, 120 V circuit; about 2,900 W on a 16 A, 230 V circuit), give every cable a drip loop, keep plugs above the highest water level, never daisy-chain power strips, and fit a working smoke alarm near the grow. Wear gloves and eye protection when handling pH acids and concentrates. (Established) - [Feeding basics: EC, the nitrogen taper, and why you don't flush](https://genetixbay.com/knowledge/guides/feeding-basics.md): Feed by EC, not by the label: start at a quarter to half the label rate, about EC 0.4–0.8 mS/cm for seedlings, 1.0–1.8 in veg and 1.6–2.2 in flower in coco and hydro (lower in soil), and raise it only while leaf tips stay clean. Feed right through to harvest. Don't flush: it starves the plant while it packs on its final weight and resin. In late flower, taper only nitrogen and keep P, K, Ca, Mg, S and the micros fed. (Supported) - [Germinating seeds step by step](https://genetixbay.com/knowledge/guides/germinating-seeds-step-by-step.md): Cannabis seeds germinate in 1–5 days when kept at 22–27 °C (72–81 °F) with steady moisture and air. Soak for no more than 12–24 h, then either plant directly 0.5–1 cm (¼–½ in) deep in moist mix or wait in a damp paper towel until the root is 0.5–2 cm long and plant it root down. Expect 80–95 % from fresh seed; old seed is slower and lower. (Supported) - [Grow journal 101: what to log and why](https://genetixbay.com/knowledge/guides/grow-journal-101.md): A grow journal is a dated record of what you did and what the plant did: daily climate and watering, weekly photos, pH, EC and height, and every event (germination, transplant, topping, flip, first pistils, problems, harvest weights). Log both days since flip and days of flower. On GenetixBay, a journal tied to a GB-ID links your harvest back to the seed pack, and herm reports and results feed the open record other growers rely on. (Grower practice) - [Legal check before you grow](https://genetixbay.com/knowledge/guides/legal-check-before-you-grow.md): Before buying anything, confirm from official sources that home cultivation is legal where you live, then check the plant limit and how it is counted, possession limits for the harvest, where plants may be kept (indoors, out of sight, locked), tenancy and building rules, rules around minors, the ban on selling, and the rules for buying and importing seed. Laws differ by country, state, province and city and change often. This guide is a dated checklist and pointer list, not legal advice. (Supported) - [Lights for beginners: how much light, PPFD and DLI made simple](https://genetixbay.com/knowledge/guides/lights-for-beginners.md): PPFD is how much usable light lands on the canopy each second (µmol/m²/s); DLI is the day's total (mol/m²/day = PPFD x hours x 0.0036). Aim for about 150–300 µmol/m²/s for seedlings (DLI 10–20), 300–600 in veg (DLI 20–40) and 600–900 in flower at 12/12 (DLI 26–39). Set height and dimming by measuring PPFD at the canopy and watching the top leaves, not by a fixed distance. (Supported) - [Pest prevention for beginners: keep them out, find them early](https://genetixbay.com/knowledge/guides/pest-prevention-for-beginners.md): Most indoor pest problems arrive on clones, plants, soil, pets or clothes, and are caught too late. Prevent them in this order: quarantine anything new for 10–14 days, start with clean media and a clean room, hang sticky traps and scout under leaves with a loupe every week, release predatory mites before you have a problem, and act at the first find rather than at the first damage. Don't spray buds in flower. Clones can also carry hop latent viroid, so buy seed or test cuts. (Supported) - [pH made simple](https://genetixbay.com/knowledge/guides/ph-made-simple.md): Keep the water you feed at pH 6.2–6.8 for soil, 5.8–6.2 for coco and 5.6–6.0 for hydro; the accepted wider ranges are about 6.0–7.0 for soil and 5.5–6.5 for soilless, and drift within them is normal. Calibrate your pH pen with pH 7 and pH 4 buffers at least weekly, add nutrients before you adjust, change pH in small drops, and check runoff weekly. Wear gloves and eye protection with acids. (Established) - [Photoperiod grow calendar: veg, flip, the 10–14 day transition, flower](https://genetixbay.com/knowledge/guides/photoperiod-grow-calendar.md): Plan a photoperiod grow in five blocks: 2 weeks of seedling, 3–6 weeks of veg at 18/6 (24/0 also works), the flip to 12/12 (13/11 also works), a 10–14 day transition before flowering really starts, then the breeder's flowering time counted from that point. So a breeder's '8 weeks' usually means harvest about 9.5–10 weeks after the flip. Log both days since flip and days of flower. (Supported) - [Reading a seed listing and buying seeds wisely](https://genetixbay.com/knowledge/guides/reading-a-seed-listing.md): Read a seed listing for what can be checked: seed type (feminised, regular or autoflower), parents and generation (F1, IBL, S1), flowering time and how it is counted, real grow journals, herm reports and lineage evidence. Distrust flower potency claims above about 35 % total cannabinoids, 'indica for sleep, sativa for energy' promises and famous names with no records. Buy small, from sellers with documented lines, and check that buying and importing seed is legal where you live. (Supported) - [Smell control and odour basics: negative pressure and carbon filters](https://genetixbay.com/knowledge/guides/smell-control-basics.md): Control grow smell by keeping the tent under negative pressure (the exhaust pulls out more air than comes in, so the walls suck in slightly) and sending every bit of exhaust through an activated-carbon filter rated at or above the fan's airflow. Size the fan for about one tent air exchange per minute plus 25–50 % for filter and duct losses. Replace the carbon every 12–18 months or when smell gets through, keep RH in range, and never use an ozone generator in an occupied home. (Grower practice) - [Soil first grow, week by week](https://genetixbay.com/knowledge/guides/soil-first-grow-week-by-week.md): A soil first grow is the most forgiving: a quality bagged potting mix with 20–35 % perlite in an 11–19 L (3–5 gal) pot, water at pH 6.2–6.8 when the pot feels light, plain water for the first 2–4 weeks while the mix's starter charge lasts, then a dilute feed at EC 0.8–1.6 mS/cm rising through flower. A photoperiod plant runs about 17–20 weeks seed to harvest: 3 weeks seedling, 3–5 weeks veg, a 10–14 day transition and 7–10 weeks of flower. (Grower practice) - [Spotting problems early: a daily five-minute check](https://genetixbay.com/knowledge/guides/daily-five-minute-check.md): Spend five minutes a day, at the same time, on one fixed routine: minute 1 the climate log, minute 2 the root zone (pot weight, reservoir or runoff), minute 3 the whole plant from a step back, minute 4 close-up under leaves with a loupe, minute 5 write it down. Most problems caught on day one are cheap to fix. When something looks wrong, check root zone and pH before blaming a nutrient, and change one thing at a time. (Supported) - [Telling sex and spotting herms: males, females and hermaphrodites](https://genetixbay.com/knowledge/guides/telling-sex-and-spotting-herms.md): Sex a cannabis plant by its first solitary flowers at the nodes, usually visible about 4–6 weeks from seed under long days: a female shows a teardrop bract with two white stigmas, a male a small round ball on a stalk with no hairs. A hermaphrodite grows both, or sprouts banana-shaped anthers in the buds. GenetixBay's position: herms are mainly breeder error that stress reveals, late-flower 'bananas' are not normal, and herm plants are culled, never bred from. Good males are valued. (Supported) - [Training basics: LST, topping and tuck-don't-pluck](https://genetixbay.com/knowledge/guides/training-basics.md): Training spreads a plant into a flat, even canopy so more bud sites sit in strong light. For a first grow, start low-stress training (bending and tying) in early veg, top photoperiods once at 4–6 nodes and allow 5–10 days of recovery, and tuck leaves out of the way rather than plucking them: leaves are the solar farm that feeds the buds. Autoflowers get LST only, not topping. Stop hard bending by mid-stretch. (Supported) - [Watering: how much, how often, by medium and pot size](https://genetixbay.com/knowledge/guides/watering-how-much-how-often.md): Water cannabis by pot weight, not by the calendar: lift the pot, and water when it feels about half as heavy as just after watering. In soil that is usually every 2–4 days, giving about 20–30 % of the pot's volume to light runoff; in coco it is daily or more, to 10–20 % runoff. Seedlings get a small ring of 50–250 mL. Overwatering, not thirst, is the most common first-grow killer. (Supported) - [When to harvest: talk to her, and read the trichome mix](https://genetixbay.com/knowledge/guides/when-to-harvest.md): Harvest when a 60x loupe shows the trichome heads on the buds as a mix of a few clear, mostly cloudy and some amber. That mix is a matter of preference, not a hard rule. Count from the flip and add the 10–14 day transition before you trust a breeder's week count, keep feeding to the end (no flush), and skip the 24–72 h of darkness: both are myths. (Grower practice) - [Your first grow, start to finish: the master guide](https://genetixbay.com/knowledge/guides/first-grow-start-to-finish.md): A first indoor grow takes about 3–5 months from seed to jar: 1 week to set up and test the room, 1–2 weeks of germination and seedling, 3–6 weeks of veg (photoperiods), a 10–14 day transition after the flip, 7–10 weeks of flower, 7–14 days of drying and at least 2–4 weeks of curing. Use one to four feminised plants, a tent, one good LED, a fan and carbon filter, 11–19 L pots, a pH pen and an EC meter, and keep a journal. (Supported) ## Basics Plant biology, life cycle, photoperiod vs auto, sex, first grows. - [Buyer beware: potency labels, strain names and other claims that don't hold up](https://genetixbay.com/knowledge/basics/buyer-beware-label-claims.md): Flower labelled above about 35% total cannabinoids is not credible: cannabinoids are made only in trichome heads, and bud is mostly bract, stem and leaf, so numbers like that belong to concentrates or to inflated testing. Studies show potency results vary systematically between labs, and retail flower labels often overstate THC. Be equally sceptical of strain names that promise effects, terpene totals far above the ~2% average, and 'indica for the couch, sativa for energy'. (Supported) - [Cannabis growing and breeding glossary](https://genetixbay.com/knowledge/basics/glossary.md): Plain-language definitions of the growing, botany and breeding terms used across GenetixBay, with notes where the popular meaning differs from the scientific one. (Established) - [Cannabis plant biology: the parts and what they do](https://genetixbay.com/knowledge/basics/cannabis-plant-biology.md): Cannabis sativa is a fast-growing annual herb in the hemp family. Most plants are either male or female, it flowers in response to long nights (unless it carries autoflower genetics), and the cannabinoids and terpenes growers want are made in glandular trichomes concentrated on the female flower heads. (Established) - [Male, female and hermaphrodite cannabis: how sex works](https://genetixbay.com/knowledge/basics/sex-male-female-hermaphrodite.md): Cannabis is dioecious: females are XX and males XY, and the species has kept separate sexes stably for millennia. Hermaphrodite (intersex) plants are unwanted outliers, mostly the result of bad breeding such as repeated selfing, careless feminising and untested seed; stress reveals the weakness in susceptible plants. Cull herm-prone plants and never breed from them. Seed from a female's own male flowers is almost all female, which is how feminised seed works and why herm tendency passes straight on. (Established) - [Photoperiod vs autoflower, and how autoflowering is inherited](https://genetixbay.com/knowledge/basics/photoperiod-vs-autoflower.md): Photoperiod cannabis flowers when nights get long; autoflowering (day-neutral) cannabis flowers by age, even under 18-24 h light. In the populations studied so far, autoflowering behaves as a single recessive gene (Autoflower1, on chromosome 1): a photoperiod x auto F1 is all photoperiod, and about 1 in 4 of its F2 plants are autos. (Supported) - [Regular, feminised, autoflower or clone: choosing your starting material](https://genetixbay.com/knowledge/basics/seed-types-regular-feminised-auto-clone.md): Regular seed gives about half males and is what breeders need; feminised seed gives nearly all females and suits growers who want flower; autoflowers flower by age; clones copy one known plant but can carry pests and viroids. Each choice changes what you can do next. (Supported) - [The cannabis life cycle, stage by stage](https://genetixbay.com/knowledge/basics/life-cycle.md): Cannabis goes from seed to seedling (1-3 weeks), vegetative growth (2-8+ weeks indoors, set by the grower for photoperiod plants), transition, flowering (about 7-12 weeks for most drug-type cultivars, longer for some tropical types) and ripening, then harvest, drying and curing. Photoperiod plants flower when nights are long enough; autoflowers flower by age. (Established) - [Your first grow: a plan from seed to jar](https://genetixbay.com/knowledge/basics/first-grow-guide.md): For a first indoor grow, use one to four plants of a reputable feminised autoflower or photoperiod line in a tent, a good LED, quality soil or coco, a pH and EC meter, and a journal. Keep the targets simple: steady temperature and humidity, light to about 400-600 µmol/m²/s in veg and 600-900 in flower, water by weight, and harvest by trichomes. (Supported) ## Germination Seed viability, germination, seedlings, damping-off, transplanting. - [Damping-off: why seedlings collapse at the soil line](https://genetixbay.com/knowledge/germination/damping-off.md): Damping-off is seedling death caused mainly by soil-borne pathogens such as Pythium, Rhizoctonia and Fusarium: the stem pinches, darkens and collapses at the soil line, or seeds rot before emerging. It is a prevention problem: clean containers and new mix, no overwatering, warm medium, good light and airflow. Once a seedling has collapsed it cannot be saved. (Established) - [Germination methods compared: soak, paper towel, plugs, direct sow](https://genetixbay.com/knowledge/germination/germination-methods.md): Cannabis seed germinates best around 20–30 °C (68–86 °F) with steady moisture and air. Every common method works if those are met: direct sowing is least handling, paper towels let you see radicles, plugs and cubes suit hydro. Lab protocols with 1 % hydrogen peroxide, short soaks or tip scarification sped up germination, mainly for old or hard seeds; they are optional for fresh seed. (Supported) - [Seed viability and storage: keeping cannabis seeds alive](https://genetixbay.com/knowledge/germination/seed-viability-storage.md): Cannabis seeds stay viable longest when dry and cold: research on hemp and drug-type seeds recommends about 5 °C (41 °F) storage to keep germination ability for around six years, with low seed moisture and an airtight container. Room temperature and humid storage cost viability within months to a few years. Test old seeds with a small germination test before planting a whole batch. (Supported) - [Seedling care: the first three weeks](https://genetixbay.com/knowledge/germination/seedling-care.md): Seedlings need moderate light (about 150–300 µmol/m²/s, 18 h, a DLI of 10–19 mol/m²/day), warm and fairly humid air (23–27 °C / 73–81 °F, 65–75 % RH), and small, careful waterings. Most seedling losses come from overwatering, too little light (stretching) or damping-off, not from lack of nutrients. Start feeding lightly once the first two or three sets of true leaves have formed. (Supported) - [Transplanting: when, into what, and avoiding transplant shock](https://genetixbay.com/knowledge/germination/transplanting.md): Transplant when roots fill the current container but before they circle: typically seedling plug to 1–3 L at 2–3 weeks, then to the final pot 2–4 weeks before flowering. Move the root ball intact into pre-moistened medium at the same pH and similar EC, water in lightly, and keep light and climate gentle for a few days. Autoflowers do best sown straight into their final pot. (Grower practice) ## Environment Temperature, humidity, VPD, airflow, CO₂ and light. - [Airflow: air exchange, canopy air speed and fan placement](https://genetixbay.com/knowledge/environment/airflow.md): Aim for gentle, constant movement across and under the canopy (roughly 0.3–1.0 m/s at leaf level) plus enough exhaust to remove heat and humidity, typically one full tent air exchange every 1–3 minutes for a lit tent. Moving air thins the leaf boundary layer, which raised canopy photosynthesis in non-cannabis research, and dries out the microclimates where mould starts. (Supported) - [CO₂ enrichment: when it pays, how much, and how to stay safe](https://genetixbay.com/knowledge/environment/co2-enrichment.md): Raising CO₂ from ambient (~420 ppm) to 800–1,200 ppm during lights-on raises cannabis photosynthesis substantially, but only pays when light is already high (roughly 900+ µmol/m²/s) and the room is sealed enough to hold it. Keep occupied rooms below the 5,000 ppm 8-hour workplace limit and never enter a room above 30,000 ppm. (Supported) - [Heat and light stress: taco leaves, bleaching and foxtails](https://genetixbay.com/knowledge/environment/heat-light-stress.md): Heat and light stress show at the top of the plant, closest to the light: leaves curl up or taco, bracts bleach white or yellow, buds may foxtail. Measure leaf temperature and canopy PPFD before blaming nutrients. Typical fixes: dim or raise the light 10–20 %, bring leaf temperature under about 30 °C (86 °F), restore airflow and root-zone water uptake. (Supported) - [Humidity by stage: RH targets from clone to cure](https://genetixbay.com/knowledge/environment/humidity-by-stage.md): Run about 65–80 % RH for clones and seedlings, 55–70 % in veg, 50–60 % early flower and 40–50 % in late flower, adjusted to hit a leaf VPD band at your temperature. High RH in flower raises bud-rot and mildew risk and, in a 2025 study, delayed flowering and lowered cannabinoids. Dry and cure near 60 % RH. (Supported) - [Light spectrum: blue, red, far-red and UV, what's real](https://genetixbay.com/knowledge/environment/light-spectrum.md): Photon quantity (PPFD/DLI) and fixture efficacy matter far more than spectrum. Less blue slightly increased cannabis yield (about 12 % from 4 % to 20 % blue). Far-red stretches plants; its yield effect is contested and seems to trade off against cannabinoid concentration. UV has repeatedly failed to raise cannabinoids in controlled trials and can cut yield at high doses. (Contested) - [Photoperiod and light leaks: 18/6, 12/12 and the dark period](https://genetixbay.com/knowledge/environment/photoperiod-light-leaks.md): Photoperiod cannabis stays vegetative under long days (18/6 up to 24/0; no sleep period is needed in veg) and flowers when the uninterrupted night is long enough: 12/12 or 13/11, and some cultivars flower at 14–15 h, usually as ~12 h at high intensity plus sunrise and sunset ramps. Light during the dark period, even very dim, can delay or weaken flowering in sensitive cultivars; leaks can also expose herm-prone genetics, triggering male flowers on susceptible plants. Some cultivars yield more at 13–14 h days, at a possible cost in THC concentration. (Supported) - [PPFD and DLI by stage, with the evidence](https://genetixbay.com/knowledge/environment/ppfd-dli-by-stage.md): In the best indoor trial, cannabis flower yield rose linearly with canopy PPFD from 120 to 1,800 µmol/m²/s at ambient CO₂ (116 to 519 g/m²) with no change in cannabinoid potency. Practical targets: 100–300 µmol/m²/s for seedlings and clones, 300–700 (up to ~900) in veg, and 800–1,200 in flower, or more with CO₂, as long as the plant shows no stress and the electricity is worth it. (Supported) - [Temperature by stage: day, night and root-zone targets](https://genetixbay.com/knowledge/environment/temperature-by-stage.md): Run roughly 24–28 °C (75–82 °F) by day in veg, 22–26 °C (72–79 °F) in flower, cooling to 20–24 °C (68–75 °F) in late flower, with nights 3–6 °C (5–10 °F) cooler. Above about 30 °C (86 °F) photosynthesis in cannabis falls unless light and CO₂ are high. Keep the root zone and hydro reservoirs at 18–22 °C (64–72 °F). (Supported) - [The flip isn't day 1 of flower: the 10–14 day transition and how to count it](https://genetixbay.com/knowledge/environment/flip-to-flower-transition.md): Switching to 12/12 starts floral induction, not flowering. In controlled studies the first visible inflorescence (at least three pairs of pistils at the top of the main shoot) appeared roughly 8–14 days after short days began, around 13–14 days on average across many hemp cultivars, and up to three weeks in slow ones. Breeder flowering times often count from that point, so a stated 8 weeks usually means harvest about 9.5–10 weeks after the flip. Count both: days since flip and days of flower. (Supported) - [VPD explained: vapour pressure deficit for cannabis growers](https://genetixbay.com/knowledge/environment/vpd-explained.md): VPD is how hard the air pulls water out of the leaf, in kPa. Common targets are about 0.4–0.8 kPa for seedlings and clones, 0.8–1.2 kPa in veg and 1.0–1.5 kPa in flower, calculated from leaf temperature rather than air temperature. Most of these bands come from grower and greenhouse practice; cannabis-specific VPD trials are still scarce. (Supported) ## Nutrients Every element, deficiencies and toxicities, feed schedules, recipes. - ["Bloom boosters" for cannabis: what's real and what's marketing](https://genetixbay.com/knowledge/nutrients/bloom-boosters.md): Most bloom boosters are concentrated phosphorus and potassium. Four independent controlled cannabis trials found no increase in flower yield or cannabinoids from raising phosphorus above roughly 25–60 mg/L, and one found no yield response to potassium anywhere from 60 to 340 mg/L. A complete, balanced flower feed is what matters; extra P and K mostly end up in the runoff and can induce magnesium, calcium, zinc and iron problems. Some boosters have been reported to contain undeclared plant growth regulators, which have no place in a consumable crop. (Supported) - [Boron (B) in cannabis: distorted tips, dying roots and a narrow safe window](https://genetixbay.com/knowledge/nutrients/boron.md): Boron cross-links cell-wall pectin and is needed wherever cells are dividing: shoot tips, root tips and flowers. Deficiency in cannabis causes stunted, distorted new growth, dead growing tips and wilting from root-tip death; toxicity scorches the margins of older leaves. Supply about 0.2–0.5 mg/L B; cannabis tolerated a tenfold dose for weeks but the gap between enough and too much is narrower than for most nutrients. (Supported) - [Building a cannabis feed by stage: ppm targets per element and how to hit them](https://genetixbay.com/knowledge/nutrients/feed-by-stage.md): A good mineral cannabis feed runs roughly N 150–200, P 30–60, K 175–250, Ca 150–200, Mg 40–70 and S 60–120 mg/L in veg and flower, plus Fe 1.5–3 and small amounts of Mn, Zn, B, Cu and Mo, at an EC of about 1.2–1.8 mS/cm in veg and 1.6–2.2 in flower. Cannabis research shows no benefit from pushing P or overall strength higher. This article gives the targets, the evidence behind each, and two worked RO-water recipes with a sources table. (Supported) - [Cal-Mag: what it is, when you need it and when you don't](https://genetixbay.com/knowledge/nutrients/cal-mag.md): Cal-Mag is a calcium and magnesium supplement, usually calcium nitrate and magnesium nitrate, sometimes with iron. You need it when your water and base nutrient together supply too little Ca and Mg: RO or very soft water, new or unbuffered coco, or a base nutrient designed for hard water. How much a plant needs is driven mainly by its cultivar, the water source, the medium (coco's cation exchange), root-zone pH and transpiration. The claim that LED lights create a Cal-Mag need is a myth. You do not need it on hard tap water with a complete base feed, and overusing it adds nitrogen and pushes potassium and magnesium out of balance. (Supported) - [Calcium (Ca) in cannabis: deficiency, transport, targets and sources](https://genetixbay.com/knowledge/nutrients/calcium.md): Calcium builds cell walls and membranes and moves only in the transpiration stream, so it cannot be moved from old leaves to new ones. Feed about 150–200 mg/L Ca in soilless systems, and remember that most 'calcium deficiency' is a delivery problem (low transpiration, high humidity, root damage, competing K/Mg/NH4) rather than an empty bottle. Classic signs are distorted, stunted new growth and brown spots. (Supported) - [Chlorine and chloride (Cl) in cannabis: a micronutrient you never need to add](https://genetixbay.com/knowledge/nutrients/chlorine.md): Chloride (Cl-) is an essential micronutrient for water splitting, osmotic balance and stomata, but the requirement is tiny and always met by water and fertiliser impurities. In practice chloride is a salinity problem, not a deficiency: keep it below roughly 50–70 mg/L in the feed, watch it in coco and some tap waters, and don't confuse chloride (a nutrient ion) with chlorine or chloramine (disinfectants). (Supported) - [Copper (Cu) in cannabis: limp, distorted new growth and root-burning excess](https://genetixbay.com/knowledge/nutrients/copper.md): Copper is needed for photosynthetic electron transport, lignin and cell-wall strength. Cannabis copper deficiency showed late as stunted, distorted, slightly yellow new leaves that lost turgor and wilted, with a 45% biomass loss. Supply only about 0.03–0.1 mg/L Cu; excess (from copper fungicides, ionisers or pipework) damages roots first. (Supported) - [Flushing before harvest: myth (summary)](https://genetixbay.com/knowledge/nutrients/flushing.md): Pre-harvest flushing is a myth that costs you yield and resin: it starves the plant while it packs on its final weight, trichomes and resin, and controlled studies found no gain in quality, minerals or cannabinoids. Cannabis stores what it takes up in its tissue, so plain water at the end doesn't wash it out. Feed through to harvest at stage-appropriate strength. The one valid flush treats the medium: a root-zone flush to clear salt build-up, at any stage. Full evidence in the flush debate article. (Myth) - [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md): Almost every mineral cannabis feed is built from about a dozen salts: calcium nitrate, potassium nitrate, monopotassium phosphate (MKP), magnesium sulfate, potassium sulfate, a few others, plus chelated iron and trace salts. Each one supplies known percentages of two elements, so 1 g/L of a salt gives (percent x 10) mg/L of each. Calcium must be kept apart from sulfate and phosphate in concentrated stocks, which is why feeds come as A and B. (Established) - [Iron (Fe) in cannabis: yellow new growth, chelates and pH](https://genetixbay.com/knowledge/nutrients/iron.md): Iron is needed to make chlorophyll and run electron transport. Deficiency shows as interveinal yellowing of the newest leaves and is almost always caused by high root-zone pH or alkaline water, not a lack of iron in the feed. Supply about 1.5–3 mg/L Fe as a chelate matched to your pH: EDTA up to about 6.5, DTPA to about 7.5, EDDHA to about 9. (Supported) - [Magnesium (Mg) in cannabis: interveinal yellowing, targets and the K-Ca competition](https://genetixbay.com/knowledge/nutrients/magnesium.md): Magnesium sits at the centre of chlorophyll. Cannabis trials put the optimum at about 35–70 mg/L Mg in veg, and Mg supply raised cannabinoid and terpene production in flower. Deficiency shows as interveinal yellowing on older leaves with green veins; it is often induced by low pH or by too much potassium or calcium rather than an actual lack of Mg. (Supported) - [Manganese (Mn) in cannabis: netted chlorosis, low-pH toxicity and the iron balance](https://genetixbay.com/knowledge/nutrients/manganese.md): Manganese is needed to split water in photosynthesis. Deficiency gives a bright yellow, netted interveinal chlorosis on upper and middle leaves with small tan spots; toxicity, usually from low root-zone pH, gives yellowing and necrosis of older leaf margins. Supply about 0.3–0.8 mg/L Mn and keep pH in range, because Mn availability swings strongly with pH. (Supported) - [Mobile vs immobile nutrients: reading old vs new leaves](https://genetixbay.com/knowledge/nutrients/mobile-vs-immobile-nutrients.md): Mobile nutrients (N, P, K, Mg, and also Cl, Mo, Ni) can be moved from old leaves to new ones through the phloem, so their shortages show on the oldest, lowest leaves first. Immobile nutrients (Ca, B, Fe, Mn, Cu, Zn, and partly S) stay where they were first deposited, so shortages show on new growth. It is the first fork in any deficiency diagnosis, with a few cannabis-specific exceptions. (Established) - [Molybdenum (Mo) in cannabis: the trace element nitrate depends on](https://genetixbay.com/knowledge/nutrients/molybdenum.md): Molybdenum is a cofactor for nitrate reductase, so a nitrate-fed plant cannot use its nitrogen without it. Cannabis needs a minuscule amount (about 0.01–0.05 mg/L Mo); in a 9-week trial, cannabis grown with no Mo showed no visible symptoms at all despite 96% lower leaf Mo. Unlike the other micronutrients, Mo becomes more available as pH rises, so deficiency is a low-pH, acid-soil problem. (Supported) - [Nickel (Ni) in cannabis: essential, needed in traces, almost never worth adding](https://genetixbay.com/knowledge/nutrients/nickel.md): Nickel became the most recently accepted essential plant micronutrient in 1987; its known job is activating urease, the enzyme that breaks down urea. Requirements are so small that contamination in salts, water and media normally covers them, and there is no published evidence of nickel deficiency in cannabis. Do not add nickel unless you feed urea in a very pure system; excess nickel is toxic and cannabis is known to accumulate metals. (Supported) - [Nitrogen (N) in cannabis: nitrate vs ammonium, deficiency, toxicity and targets](https://genetixbay.com/knowledge/nutrients/nitrogen.md): Nitrogen drives leaf growth and photosynthesis. Cannabis does best on mostly nitrate N (about 150–200 mg/L in soilless veg and early flower), with ammonium kept at or below about 10–30% of total N; above 30% ammonium, cannabis trials show toxicity and lost yield. Deficiency yellows the oldest leaves first; excess gives dark, clawed leaves and soft, leafy growth. (Supported) - [Nutrient antagonism and Mulder's chart: what the evidence actually says](https://genetixbay.com/knowledge/nutrients/nutrient-antagonism.md): Mulder's chart is a mid-20th-century wheel of nutrient interactions. It is a useful reminder that excess of one nutrient can suppress another, but it is a teaching sketch, not a quantitative tool. A review of 117 published interactions found synergy far more often than antagonism; the antagonisms that reliably matter in practice are among cations (K, Ca, Mg, NH4, Na), phosphorus with zinc and iron, and iron with manganese. (Supported) - [Organic vs mineral nutrition for cannabis: what the trials show](https://genetixbay.com/knowledge/nutrients/organic-vs-mineral.md): Plants absorb the same ions whether they came from a bag of salts or from compost; the differences are in speed, precision and what else comes along. Controlled cannabis trials show mineral feeds deliver nutrients more efficiently and organic liquid feeds need higher nominal N to match them. Organic and lower-input regimes can keep cannabinoid content per gram up while yield falls. Plants mostly don't care where the ions come from; slight differences in flavonoids or terpenes are possible but unproven, and no controlled blind trial shows organic flower tastes better. (Supported) - [Per-element feeding tricks: what growers adjust, stage by stage](https://genetixbay.com/knowledge/nutrients/per-element-tricks.md): Experienced growers change single elements by stage rather than just turning the whole feed up or down: tapering nitrogen in late flower, cutting the ammonium share after the flip, a little extra calcium through the stretch, small magnesium, boron and zinc bumps in flower, silicon in veg. Most of these tricks are grower practice with little or no controlled research behind them. Two popular ones are contradicted by research: extra phosphorus above about 30–60 mg/L and potassium 'ramps' above about 250 mg/L did not raise yield or cannabinoids in controlled cannabis trials. Sugars and molasses feed soil microbes only, not the plant, and do harm in hydro. The GenetixBay approach is to taper nitrogen and keep everything else fed, which needs single salts or per-element dosing. (Grower practice) - [Phosphorus (P) in cannabis: what it does, deficiency, excess and how much is enough](https://genetixbay.com/knowledge/nutrients/phosphorus.md): Phosphorus powers energy transfer (ATP), roots and flowering, but cannabis needs far less than 'bloom' marketing implies. Controlled trials found no yield or cannabinoid gain above roughly 25–60 mg/L P in solution; extra P just ends up in the runoff and can tie up zinc, iron and calcium. Deficiency shows as dark, dull, olive-spotted older leaves and stunting. (Supported) - [Potassium (K) in cannabis: role, deficiency, excess and K-Ca-Mg balance](https://genetixbay.com/knowledge/nutrients/potassium.md): Potassium runs water relations, stomata and sugar transport. Cannabis grows well on roughly 175–240 mg/L K in veg, and a flowering DWC trial found no yield response anywhere between 60 and 340 mg/L K, so more is not better. Deficiency scorches the margins and serrations of older leaves; excess K mainly does harm by suppressing calcium and magnesium uptake. (Supported) - [Silicon (Si) for cannabis: beneficial, not essential, and how to dose it](https://genetixbay.com/knowledge/nutrients/silicon.md): Silicon is a beneficial element, not an essential one. It strengthens cell walls and reduces abiotic and some disease stress in many crops, and cannabis does take it up, but cannabis-specific evidence for yield or quality benefits is thin. If you use it, add potassium silicate first to the water at about 20–50 mg/L Si, before other nutrients, and correct pH afterwards because it is strongly alkaline. (Contested) - [Sodium (Na) and cannabis: a salt to keep low, not a nutrient to add](https://genetixbay.com/knowledge/nutrients/sodium.md): Sodium is not essential for cannabis. It can partly substitute for potassium in some plants, but in cannabis the controlled data show only harm: cannabinoids fall linearly as NaCl rises, and more than about 5 mM NaCl (115 mg/L Na) may reduce yield in hydro. Keep sodium below about 50 mg/L in the feed, never use ion-exchange softened water, and watch it build up in coco and recirculating systems. (Supported) - [Sulfur (S) in cannabis: role, deficiency, targets and sulfate sources](https://genetixbay.com/knowledge/nutrients/sulfur.md): Sulfur is part of the amino acids cysteine and methionine and of glutathione; cannabis also makes sulfur-containing aroma compounds. Feeds usually supply 50–120 mg/L S as sulfate without trying, via magnesium and potassium sulfate. Deficiency yellows the middle and newer leaves evenly, strongest at the leaflet base, and is rare unless a feed is built entirely from nitrates and chlorides. (Supported) - [Zinc (Zn) in cannabis: small leaves, margin burn and the phosphorus link](https://genetixbay.com/knowledge/nutrients/zinc.md): Zinc is needed for many enzymes and for making the growth hormone auxin. Deficiency in cannabis shows late, as yellowing and then tan necrosis along the toothed margins of new leaves, often with small leaves and short internodes elsewhere in the literature. Supply about 0.1–0.5 mg/L Zn; high pH and very high phosphorus are the usual reasons a fed plant runs short. (Supported) ## pH and EC pH, EC and ppm scales, water quality, runoff, drift. - [Buffering coco coir: why it matters and how to do it](https://genetixbay.com/knowledge/ph-ec/buffering-coco.md): Coco coir has a high cation exchange capacity that arrives loaded with potassium and sodium. Unbuffered, it grabs calcium and magnesium from your feed and releases K and Na, causing early Ca/Mg deficiency. Buffering means soaking washed coco in a calcium (and usually magnesium) nitrate solution so the exchange sites are filled with Ca and Mg before planting, then rinsing. It is standard grower and industry practice with sound chemistry behind it, though controlled studies on cannabis are lacking. (Grower practice) - [EC vs PPM: the 500 and 700 scales, CF, and how to convert](https://genetixbay.com/knowledge/ph-ec/ec-ppm-scales.md): EC (electrical conductivity, in mS/cm) is what every meter actually measures. 'PPM' or TDS readings are EC multiplied by an assumed factor: 0.5 on the 500 (NaCl) scale, 0.7 on the 700 (442 or KCl-style) scale, sometimes 0.64. So 1.0 mS/cm reads 500 ppm on one meter and 700 ppm on another. Always talk in EC, or state the scale. Feed charts quoting ppm without a scale are ambiguous by 40%. (Established) - [pH and EC meter calibration: buffers, slope, storage and when to replace a probe](https://genetixbay.com/knowledge/ph-ec/meter-calibration.md): Calibrate pH meters with at least two fresh buffers that bracket your readings (pH 7 then pH 4 for growing), before any session where decisions matter and at least weekly. Store glass pH probes wet in storage solution or pH 4/7 buffer, never in RO water or dry. Check EC meters against a 1.413 mS/cm standard. A pH probe with a slope below about 90-95% or one that can no longer be adjusted to buffer should be replaced; typical glass electrodes last one to two years. (Established) - [pH and nutrient availability: what pH really controls, by medium](https://genetixbay.com/knowledge/ph-ec/ph-nutrient-availability.md): pH controls how soluble each nutrient is and how well roots absorb it. The accepted ranges are soil about 6.0–7.0 and soilless/hydro about 5.5–6.5 (sweet spots: 5.5–6.2 in hydro, 5.8–6.3 in coco and rockwool, 6.2–6.8 in soil), and drift within the range is normal. High pH starves plants of iron, manganese, zinc, boron and phosphorus; low pH makes iron and manganese overly available and reduces calcium, magnesium and molybdenum. The classic availability bar chart was built for mineral soils and overstates the effect in chelated soilless feeds. The ranges are broadly agreed accepted practice, from extension and grower consensus. (Established) - [pH drift in hydro: why reservoir pH rises (and sometimes falls)](https://genetixbay.com/knowledge/ph-ec/ph-drift-hydro.md): Reservoir pH usually rises because plants absorb nitrate and release hydroxide or bicarbonate to stay electrically balanced; aeration driving off CO2, alkaline top-up water and algae add to it. Ammonium does the opposite. A steady upward drift of a few tenths per day in a healthy, growing system is normal. Manage it with a small ammonium share (5–15% of N), acidifying alkaline water, and letting pH ride within 5.5–6.2 rather than chasing a single number. A fast unexplained fall, or a rise with brown roots, points to root or microbial trouble. (Established) - [Runoff testing: how to measure root-zone pH and EC and what the numbers mean](https://genetixbay.com/knowledge/ph-ec/runoff-testing.md): Runoff (leachate) pH and EC tell you what the roots are actually sitting in, which is often different from what you fed. Use the pour-through method: water to full saturation, wait 30 minutes to 2 hours, then pour a measured amount of water on top and collect about 50 mL. Compare runoff EC with input EC: higher means salts are building up, much lower means the plant is hungry or you are over-leaching. Track the trend over weeks rather than reacting to one reading. (Supported) - [Water quality for cannabis: RO vs tap, alkalinity, bicarbonates and chloramine](https://genetixbay.com/knowledge/ph-ec/water-quality.md): Get a water report before choosing a feed. Alkalinity (bicarbonate), not water pH, is what pushes root-zone pH up over time; above about 100–150 mg/L as CaCO3 (2–3 meq/L) it should be partly neutralised with acid. Tap water may also add useful Ca and Mg, or harmful sodium, chloride and boron. RO water removes nearly everything, which gives precise control but means you must add back Ca and Mg. Chloramine does not evaporate; remove it with long-contact or catalytic carbon or ascorbic acid if you run living soil or beneficial microbes. (Supported) ## Systems Soil, coco, rockwool, living soil and every hydro system. - [Bottom-watering, soak trays and wick (self-watering) systems](https://genetixbay.com/knowledge/systems/bottom-watering-wick.md): Bottom-watering lets pots draw solution up from a tray, either by a timed soak (flood 2–5 cm for 10–30 minutes, then drain) or by a constant shallow level held by a float valve or wick. It is gentle and labour-saving and suits soil, but salts accumulate at the top of the pot, so feed at lower EC than top-feeding and top-water to runoff every week or two. (Supported) - [Choosing your growing system: soil, coco, rockwool or hydro](https://genetixbay.com/knowledge/systems/choosing-a-system.md): Choose by how much attention and measurement you can give, not by yield claims. Soil and living soil forgive mistakes for days; coco and drip need daily feeding; DWC, NFT and aeroponics grow fast but can lose roots within hours if a pump or air supply fails. No controlled study shows one system out-yielding the others when light and climate are equal. (Grower practice) - [Deep water culture (DWC)](https://genetixbay.com/knowledge/systems/dwc.md): In DWC roots hang in an aerated nutrient solution. It grows fast but depends on two things: dissolved oxygen (keep above about 6 mg/L, ideally near saturation) and solution temperature (18–22 °C / 64–72 °F). Warm, poorly aerated water is how Pythium root rot starts. Run pH 5.6–6.0 and EC 0.8–2.0 mS/cm by stage, and treat the air pump as life support. (Supported) - [Drain-to-waste drip and crop steering (generative vs vegetative dryback)](https://genetixbay.com/knowledge/systems/drain-to-waste-crop-steering.md): Drain-to-waste drip sends fresh solution every shot and discards runoff, so you control the root zone by irrigation timing, shot size and substrate EC measured with a VWC/EC probe. Vegetative steering uses earlier first shots, larger shots and small overnight drybacks (about 10–15 % VWC); generative steering delays the first shot, uses smaller shots, longer P3 and larger drybacks (about 20–35 %) with higher substrate EC. The ranges are grower practice; one cannabis study found controlled late-flower drought raised cannabinoid concentration. (Grower practice) - [Ebb and flow (flood and drain)](https://genetixbay.com/knowledge/systems/ebb-and-flow.md): A pump floods a table or tray of pots to a standpipe height, then the solution drains back to the reservoir. Each flood refreshes water and pulls fresh air into the medium as it drains. Typical schedules: clay pebbles 3–6 floods per light period of 10–15 minutes, coco or rockwool 1–3. It is robust because the media buffer pump failures for days, but salts can build up at the top of the medium. (Supported) - [Fogponics: ultrasonic fog for roots (a supplement, not a system)](https://genetixbay.com/knowledge/systems/fogponics.md): Fogponics uses ultrasonic transducers to make a 5–10 µm water fog that is blown into a root chamber. Fog carries very little dissolved nutrient (salts stay behind and concentrate in the fogger tank), transducers wear out in roughly 1,000–3,000 hours and run hot, so GenetixBay treats fog as a humidity supplement for cloning domes and aeroponic chambers, not as a standalone way to feed a flowering plant. (Grower practice) - [Growing in coco coir](https://genetixbay.com/knowledge/systems/coco.md): Coco coir is a hydroponic substrate that looks like soil: inert-ish, airy, and fed every irrigation with a complete mineral solution at pH 5.8–6.2 and EC 1.2–2.4 mS/cm with 10–20 % runoff. Use pre-washed, buffered coco or buffer it yourself with a calcium/magnesium solution, because raw coir holds potassium and sodium and grabs calcium and magnesium. (Supported) - [Growing in rockwool (stonewool cubes and slabs)](https://genetixbay.com/knowledge/systems/rockwool.md): Rockwool is an inert, unbuffered mineral fibre that holds a lot of water and air and gives precise control over the root zone. Pre-soak at pH about 5.5, run pH 5.5–6.0 and EC 1.8–3.0 mS/cm in flower, and manage it by volumetric water content and slab EC. It is the native medium of crop steering, and it punishes neglect quickly because nothing buffers mistakes. (Supported) - [Growing in soil (potting mix with bottled feed)](https://genetixbay.com/knowledge/systems/soil.md): Soil (a peat- or compost-based potting mix fed with dilute bottled nutrients) is the most forgiving system: it buffers pH and nutrients and holds water for days. Water to light runoff when the pot is light, feed at EC 0.8–1.6 mS/cm with water at pH 6.2–6.8, and remember that over-watering, not under-feeding, kills most soil plants. (Supported) - [High-pressure aeroponics (HPA)](https://genetixbay.com/knowledge/systems/hpa-aeroponics.md): HPA atomises nutrient solution at roughly 80–100 psi (5.5–7 bar) through fine nozzles into a root chamber, giving fine droplets (about 10–100 µm) and very high root oxygen. It can grow outstanding root systems but has the shortest failure margin of any system: roots can be damaged within tens of minutes if misting stops. It needs an accumulator, pressure monitoring, filtration, anti-drip nozzles and a backup plan. (Supported) - [Kratky (passive, non-circulating hydroponics)](https://genetixbay.com/knowledge/systems/kratky.md): Kratky is hydroponics with no pump: the plant sits above a container of nutrient solution, drinks it down, and the growing air gap gives the upper roots oxygen. It was developed and published for lettuce and tomatoes at the University of Hawaii. Cannabis can be grown this way, but its large water use means big containers, careful refills that keep the air gap, and close attention to water temperature and EC drift. (Supported) - [Living soil (no-till, water-only organic growing)](https://genetixbay.com/knowledge/systems/living-soil.md): Living soil is a large, biologically active, amended organic soil that is reused without tilling and watered with plain dechlorinated water; soil organisms release nutrients. It is forgiving and low-input once established but slow to correct, so build it well, keep it moist and mulched, never use salt-based nutrients or sanitisers on it, and don't chase pH. Most of its claims are grower practice rather than tested in cannabis. (Grower practice) - [Low-pressure aeroponics (LPA)](https://genetixbay.com/knowledge/systems/lpa-aeroponics.md): LPA uses an ordinary submersible pump and spray heads to drench roots hanging in a dark chamber with coarse droplets. It is essentially a spray-assisted hydro system: forgiving (a pool on the chamber floor keeps roots wet for hours), cheap, and easier than true high-pressure aeroponics. Run sprays continuously or on short cycles such as 1 minute on, 4 off, with a chamber humidity watchdog and solution at 18–22 °C. (Supported) - [Nutrient film technique (NFT)](https://genetixbay.com/knowledge/systems/nft.md): In NFT a thin, continuous film of nutrient solution runs down sloped channels past bare roots. It is efficient and well proven for lettuce and herbs, but large cannabis root masses can dam the channel, and roots dry within one to three hours if the pump stops. Keep flow continuous (about 1–2 L/min per channel), slope about 1:30 to 1:100, and solution at 18–22 °C. (Supported) - [Recirculating deep water culture (RDWC)](https://genetixbay.com/knowledge/systems/rdwc.md): RDWC links several DWC sites to a control bucket and circulates the solution with a pump, so one reservoir sets pH, EC and temperature for every plant and a single chiller cools the lot. It adds circulation and plumbing failure modes to DWC's oxygen and temperature risks. Targets match DWC: 18–22 °C, DO above 6 mg/L, pH 5.6–6.0. (Grower practice) - [Recirculating drip (top-feed, runoff returns)](https://genetixbay.com/knowledge/systems/recirculating-drip.md): A pump pushes nutrient solution through drip emitters into pots of coco, rockwool or clay pebbles and the runoff returns to the reservoir. It saves water and nutrients but the reservoir slowly drifts as runoff brings back salts and root exudates, so monitor runoff and refresh when reservoir chemistry diverges. Typical shots are 2–6 % of pot volume, first shot 1–2 h after lights-on, none in the dark. (Supported) ## Training Topping, LST, SCROG, SOG, mainlining, defoliation. - [Defoliation and lollipopping: what to remove, when, and the evidence](https://genetixbay.com/knowledge/training/defoliation-lollipopping.md): Lollipopping strips small branches and leaves from the shaded lower third at or near the flip; defoliation removes fan leaves that shade bud sites or block airflow. In a controlled study on large plants, neither defoliation three weeks before harvest nor lower-branch removal changed flower or cannabinoid yield per plant, and defoliation improved cannabinoid uniformity. Stripping within reason doesn't hurt yield, but in the founder's experience tucking helps more: tuck and train first. Whether tucking beats stripping, and whether defoliation raises cannabinoids, is an open GenetixBay trial question. (Supported) - [FIM: pinching most of the tip for multiple tops](https://genetixbay.com/knowledge/training/fim.md): FIM removes roughly 70–80 % of the newest growth at the tip instead of cutting cleanly above a node. When it works, three to five shoots grow from the same point; when it doesn't, you get one or two, like a sloppy top. It is less predictable than topping and has no controlled research behind its yield claims. (Grower practice) - [HST and supercropping: controlled stem crushing](https://genetixbay.com/knowledge/training/hst-supercropping.md): Supercropping pinches and gently crushes a green stem until the inner tissue softens, then bends it over so the tip sits lower. It is used to tame tall shoots in late veg and early stretch. Done right the stem forms a firm knuckle in a few days. Stem snapping gives better buds in the founder's long experience: *Grower practice*, house-endorsed, though no controlled study has measured a potency gain yet. Every cultivar responds differently. (Grower practice) - [LST: low-stress training](https://genetixbay.com/knowledge/training/lst.md): Low-stress training bends and ties stems outward and down so the plant grows as a flat, even canopy, without cutting anything. It is the safest training method, suits autoflowers, and works with topping and SCROG. Start in early veg, adjust ties every few days, and stop bending hard once stems lignify in mid-stretch. (Grower practice) - [Mainlining and manifolding: building a symmetrical plant](https://genetixbay.com/knowledge/training/mainlining-manifolding.md): Mainlining (manifolding) tops a young plant down to the third node, removes all lower growth, and then tops each arm repeatedly to build a symmetrical hub feeding 8 or 16 evenly matched colas. It produces a very even canopy at the cost of 2–4 extra weeks of veg. It is grower practice with no controlled studies; the closest research found double pruning increased yield per plant. (Grower practice) - [SCROG: screen of green](https://genetixbay.com/knowledge/training/scrog.md): SCROG uses a horizontal net 20–40 cm above the pots to spread a few plants into a flat, even canopy: shoots are tucked under the net through veg and early stretch, then allowed to grow up through it. It suits small rooms and plant-count limits, at the cost of longer veg. Fill about 70–80 % of the net before flipping, since plants stretch to fill the rest. (Grower practice) - [SOG: sea of green](https://genetixbay.com/knowledge/training/sog.md): Sea of green packs many small plants, usually clones, into the space and flowers them after little or no veg, so each plant makes one main cola. Higher planting density increases yield per square metre but lowers cannabinoid uniformity between plants, according to controlled research. Typical densities are 9–25 plants per m² with 0–14 days of veg; check local plant-count rules first. (Supported) - [Topping: cutting the main tip for more colas](https://genetixbay.com/knowledge/training/topping.md): Topping removes the main growing tip above a node so the two shoots below take over, breaking apical dominance and producing a flatter plant with more main colas. Top healthy plants with 4–6 nodes, cut just above the chosen node, and allow 5–10 days of recovery before flipping to flower. In one controlled study, pruning twice (at transplant and at the switch to flower) gave the highest flower and cannabinoid yield per plant. (Supported) ## Pests Identification, life cycles, thresholds and IPM. - [Aphids on cannabis: species, life tables, population growth and IPM](https://genetixbay.com/knowledge/pests/aphids.md): Three aphids matter on cannabis: the cannabis-only cannabis aphid (Phorodon cannabis), the green peach aphid (Myzus persicae) and the cotton/melon aphid (Aphis gossypii). All breed without mating and give live birth, with intrinsic rates of increase of about 0.25-0.53 per day at 25 C, so a colony doubles every 1.3-2.8 days. Identify the species, then release the matching parasitoid early; keep sprays out of flower. (Established) - [Broad mites on cannabis: life table, spread and control (plus russet mite summary)](https://genetixbay.com/knowledge/pests/broad-russet-mites.md): Broad mites (Polyphagotarsonemus latus) twist, glaze and harden cannabis new growth. At 25 C a generation takes about 4.4 days from egg to adult and populations can double in about 2.2 days (grape-leaf lab data), so control rests on clean stock, quarantine, preventive predatory mites (Amblyseius swirskii, Neoseiulus cucumeris, N. californicus) and repeat treatments timed to the life cycle. Hemp russet mite has its own article. (Supported) - [Budworms on cannabis: corn earworm and tobacco budworm in numbers](https://genetixbay.com/knowledge/pests/budworms-corn-earworm.md): The 'budworm' that ruins outdoor cannabis colas in the US is mostly the corn earworm (Helicoverpa zea), with the tobacco budworm (Chloridea virescens) mixed in; both need about 422 Celsius degree-days above 12.6 C to go from egg to adult (about 34 days at 25 C), lay up to ~1,500 eggs per female singly on flowers, and open the door to bud rot, so growers trap moths from late July, scout buds weekly in flower and hit hatchlings with Bt within the first week after egg hatch. (Supported) - [Cannabis aphid (Phorodon cannabis): ID, life table, overwintering and control](https://genetixbay.com/knowledge/pests/cannabis-aphid.md): The cannabis aphid (Phorodon cannabis) develops only on Cannabis. It was first recognised as a pest in North America on Colorado hemp from 2015. On hemp at 25 C it starts breeding 6.4 days after birth, produces about 112 nymphs per female and doubles every 2 days (r_m 0.355/day), but it nearly stops growing at 30 C. Short days trigger males and egg-laying females outdoors and after the indoor flip. Quarantine clones; no parasitoid has been proven against it in peer-reviewed trials. (Supported) - [Caterpillars on cannabis: species, degree-days and control](https://genetixbay.com/knowledge/pests/caterpillars.md): Caterpillars on cannabis are mostly an outdoor, late-season problem: corn earworm budworms bore into colas and start bud rot, European corn borer and Eurasian hemp borer tunnel stems and buds, and armyworms and loopers chew leaves. Each species has a degree-day clock (lower thresholds about 10-14 C), so trap the moths, scout for eggs and hatchlings, exclude moths with netting, and use Bt or other biologicals on newly hatched larvae before they bore in. (Supported) - [Fungus gnats: the watering problem with wings](https://genetixbay.com/knowledge/pests/fungus-gnats.md): Fungus gnats (Bradysia impatiens, B. coprophila) breed in constantly wet, organic, microbially active media. At about 25 C a generation takes roughly 17-22 days and the population can double about every 6 days (r_m 0.111/day). Larvae chew roots of seedlings and clones and can carry Pythium; adults do not. Dry the top of the medium, then use Bti, Steinernema feltiae, Stratiolaelaps scimitus or Dalotia coriaria, with yellow cards and potato slices to count. (Established) - [Hemp russet mite (Aculops cannabicola): life cycle, detection and control](https://genetixbay.com/knowledge/pests/hemp-russet-mite.md): Hemp russet mite (Aculops cannabicola) is a 0.11-0.21 mm eriophyid mite that lives only on Cannabis, bronzes and curls leaves upward from the lower canopy and moves into buds. It is invisible below about 15-20x and needs about 55x to count. No life table exists for it; its relative the tomato russet mite completes egg-to-adult in 5.5 days at 25 C with an r_m of 0.286 per day. Clean stock and quarantine are the main defences; most growers treat it as zero tolerance in mothers and clones. (Supported) - [Integrated pest management (IPM) for cannabis: a complete programme for home and small commercial growers](https://genetixbay.com/knowledge/pests/integrated-pest-management-program.md): A cannabis IPM programme is a written routine: keep pests out (clean stock, a 14-21 day quarantine, clean-room-first workflow), find them early (weekly leaf and card scouting with set thresholds), act by life stage and temperature (predators first, contact tools only in veg, rotation by mode-of-action group), and record every count so the next run starts smarter. (Supported) - [Leafhoppers on cannabis: beet leafhopper, curly top and hopperburn](https://genetixbay.com/knowledge/pests/leafhoppers.md): Leafhoppers matter on cannabis for one reason above all: the beet leafhopper (Circulifer tenellus) spreads beet curly top virus, which was found in 81% of symptomatic hemp samples in Colorado in 2019 and has no cure. Potato leafhopper causes hopperburn but is usually a minor pest. Protect young outdoor plants with barriers, control weed hosts, monitor with yellow sticky cards and rogue infected plants; insecticides cannot stop a virus transmitted within hours. (Supported) - [Mealybugs and root mealybugs on cannabis: ID, life cycle in numbers and IPM](https://genetixbay.com/knowledge/pests/mealybugs.md): Mealybugs are occasional, slow-building pests of indoor cannabis, usually the citrus mealybug (Planococcus citri), sometimes the longtailed mealybug or root mealybugs (Rhizoecus). They are slow: about 4 weeks egg to adult at 25 °C and an r_m near 0.084/day (doubling in about 8 days, lab data on grapevine), with development failing at 35 °C. Wax shields them from contact sprays, ants farm them, and control rests on clean clones, ant control, and Cryptolaemus and Leptomastix released above about 20 °C. (Supported) - [Root aphids (rice root aphid) on indoor cannabis: ID, life cycle in numbers and IPM](https://genetixbay.com/knowledge/pests/root-aphids.md): The 'root aphid' of indoor cannabis in North America is mainly the rice root aphid (Rhopalosiphum rufiabdominale). At 25 °C it doubles in about 1.6 days (r_m 0.432/day, lab data from Tsai and Liu 1998), it reproduces only asexually indoors, and winged alates spread it plant to plant. Control rests on clean clones, removing every root between runs, a plant-free gap, and fungal drenches; nematodes and soil predators are unproven. (Supported) - [Shore flies: algae farmers in your propagation tray](https://genetixbay.com/knowledge/pests/shore-flies.md): Shore flies (Scatella stagnalis, S. tenuicosta) breed in algae on wet media, rockwool, benches and floors. Larvae eat algae, not roots, but larvae and adults carry Pythium, Thielaviopsis, Fusarium and Verticillium in their gut and frass. At 25 C S. stagnalis goes egg to adult in 11.4 days and multiplies at r_m 0.263/day. Control is algae and puddle management first; Bti and soil mites do little, rove beetles and repeated nematode drenches help. (Established) - [Slugs and snails: night shift on your seedlings](https://genetixbay.com/knowledge/pests/slugs-and-snails.md): Slugs and snails, above all the gray field slug Deroceras reticulatum, chew smooth-edged holes in cannabis seedlings and young transplants at night in cool, wet weather. They lay clutches of about 10-40 eggs and do best near 17-20 C. Scout at night or under boards, protect seedlings with iron phosphate baits, copper barriers and traps, and remove hiding places. (Established) - [Spider mites on cannabis: life tables, ID and IPM](https://genetixbay.com/knowledge/pests/spider-mites.md): The twospotted spider mite (Tetranychus urticae) causes pale stippling and, at high numbers, webbing on cannabis. In lab life tables its intrinsic rate of increase roughly doubles from about 0.16 per day at 20 °C to about 0.30 per day at 30 °C, so 10 females can become several thousand in three weeks in a warm room. Control rests on early scouting, cooler and less dry veg rooms, predatory mites released early, and contact sprays timed to the egg stage and kept out of flower. (Established) - [Temperature, humidity and pest population growth in cannabis: every major pest compared](https://genetixbay.com/knowledge/pests/temperature-humidity-and-pest-population-growth.md): Room temperature is the single biggest lever on how fast cannabis pests multiply: between about 20 and 30 C, most mites, aphids and thrips double every 2-4 days in lab life tables, while mealybugs and fungus gnats double every 6-8 days. Humidity matters mostly through the predators and pathogens that control pests, so set-points should be chosen for the beneficials as much as against the pest. (Supported) - [Thrips on cannabis: life table, temperature, scouting and biological control](https://genetixbay.com/knowledge/pests/thrips.md): Thrips rasp leaf cells and leave silvery scars dotted with black fecal specks. Western flower thrips needs about 268 degree-days above 7.9 °C per generation (about 16 days at 25 °C) and can grow by r = 0.12-0.23 per day. Eggs sit inside leaf tissue and most pupae sit in the medium, so control has two levels: predators that eat larvae on the foliage, and soil predators or nematodes for the pupae, all set up in veg. (Established) - [Two-spotted vs carmine spider mite: one species or two, and does it matter?](https://genetixbay.com/knowledge/pests/two-spotted-vs-carmine-mite.md): The carmine spider mite (Tetranychus cinnabarinus) is now usually treated as the red form of the twospotted spider mite, Tetranychus urticae, because red and green mites interbreed, overlap in every morphological character and do not separate in DNA studies. Some researchers still use the old name. For a cannabis grower the colour form changes almost nothing: the same predators, the same humidity and temperature logic and the same acaricide rotation apply; resistance depends on a population's spray history, not its colour. (Supported) - [Whiteflies on cannabis: life table, temperature, parasitoids and IPM](https://genetixbay.com/knowledge/pests/whiteflies.md): Whiteflies are tiny white moth-like sap feeders that rise in a cloud when you shake a plant; nymphs sit flat under leaves and drip honeydew. Greenhouse whitefly needs about 381 degree-days above 8.3 °C per generation (about 23 days at 25 °C) and prefers moderate rooms; silverleaf whitefly grows fastest at 25-27 °C (r about 0.19 per day). Identify the species, monitor with yellow cards, and release Encarsia formosa (greenhouse whitefly, rooms above about 18-20 °C) or Eretmocerus (silverleaf, warm rooms) plus A. swirskii early in veg, keeping sprays out of flower. (Supported) ## Diseases Mildew, botrytis, root rot, viruses and viroids, sanitation. - [Botrytis (bud rot / grey mould) in cannabis](https://genetixbay.com/knowledge/diseases/botrytis-bud-rot.md): Bud rot is Botrytis cinerea rotting dense colas from the inside, favoured by cool-to-moderate temperatures (10–27 °C, optimum near 20 °C), high humidity and free water on tissue. There is no cure in flower: prevent it with RH below about 50 % in late flower, dew-point control at lights-off, airflow, open canopies and fast removal of infected buds. (Established) - [Fusarium in cannabis: wilt, crown rot and bud rot](https://genetixbay.com/knowledge/diseases/fusarium.md): Fusarium fungi cause three different problems in cannabis: vascular wilt (F. oxysporum), root and crown rot (mainly F. solani), and a pinkish-white bud rot. There is no cure once a plant is infected; remove it, stop root-zone stress, sanitise pots and water, and source clean clones and media. (Established) - [Hop latent viroid (HLVd, 'dudding') and other cannabis viruses](https://genetixbay.com/knowledge/diseases/hop-latent-viroid-and-viruses.md): Hop latent viroid is a tiny infectious RNA that spreads through sap on tools, hands, clones, recirculating water and seed, and causes 'dudding': stunting, brittle stems and small, low-resin flowers. There is no cure in a plant. Test mothers (roots and leaves) by RT-PCR/RT-qPCR, discard positives, disinfect tools with bleach or heat (not alcohol), and use meristem tissue culture to rescue valuable genetics. (Supported) - [Powdery mildew in cannabis](https://genetixbay.com/knowledge/diseases/powdery-mildew.md): Powdery mildew is a leaf-surface fungus (mainly Golovinomyces ambrosiae) that thrives in still, humid, moderate-temperature canopies and spreads by airborne spores. Prevent it with airflow, stable humidity, clean clones and resistant genetics; treat early in veg with least-toxic contact options, because once it reaches flowers there is no clean fix. (Established) - [Root rot and Pythium in cannabis](https://genetixbay.com/knowledge/diseases/root-rot-pythium.md): Pythium root rot is a water mould that thrives in warm, low-oxygen root zones and swims between plants in recirculating water. Brown, slimy roots whose outer layer slides off, plus wilting with a wet root zone, are the signature. Fix the root-zone conditions first: solution at about 18–21 °C (65–70 °F), high dissolved oxygen, clean water and no overwatering; then remove dead roots and re-establish beneficial microbes. (Established) - [Sanitation and disease prevention for cannabis grows](https://genetixbay.com/knowledge/diseases/sanitation-and-prevention.md): Most cannabis disease problems are brought in on clones, tools, hands, media or water, and then helped along by humid, stagnant rooms. Quarantine and test incoming plants, work clean-to-dirty, clean then disinfect with the right chemical class for the pathogen (bleach or hypochlorous acid or heat for viroids; alcohol and peroxide do not inactivate HLVd), treat recirculating water, and keep the climate out of the disease zone. (Supported) - [Septoria leaf spot (yellow leaf spot) in cannabis](https://genetixbay.com/knowledge/diseases/septoria-leaf-spot.md): Septoria leaf spot (Septoria cannabis) starts as small brown spots with bright yellow halos on lower, older leaves and climbs the plant in wet, humid weather by rain and water splash. It is mainly an outdoor and greenhouse problem; manage it with clean lower canopies, dry foliage, mulch, airflow and debris removal, and protectants only where registered. (Supported) ## Diagnosis Symptom-led decision trees: start here when something looks wrong. - [Brown or burnt leaf tips on cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/brown-burnt-tips.md): Crispy brown tips on otherwise healthy leaves usually mean too much salt in the root zone (EC too high, or salts building up because of low runoff or drying out), not a deficiency. Check runoff or reservoir EC against input first, then watering rhythm, then heat and low humidity, and only then K or B disorders. (Supported) - [Brown roots in hydroponics (DWC, RDWC, NFT): a differential](https://genetixbay.com/knowledge/diagnosis/root-browning-hydro.md): Healthy hydro roots are white to cream and firm. Brown roots that are still firm and odourless are often just stained by nutrients or additives; brown, slimy, smelly roots whose outer layer slips off are root rot, usually Pythium, favoured by warm, oxygen-poor solution. Check solution temperature and dissolved oxygen first, then root texture and smell. (Supported) - [Cannabis bud problems: the master decision tree](https://genetixbay.com/knowledge/diagnosis/bud-problems-decision-tree.md): Check buds for rot first: a brown, dead sugar leaf in a healthy cola, or grey fuzz inside, is Botrytis and needs the bud cut out today. Then look for white powder (powdery mildew), bananas or seeds (a hermaphrodite: a genetic defect, never normal), frass and holes (caterpillars), white or bleached tops (too much light), foxtails, and loose, airy buds (usually too little light at the bud site). Most bud problems are decided by where on the plant they appear and what the canopy climate was. (Supported) - [Cannabis lookalike problems: how to tell them apart](https://genetixbay.com/knowledge/diagnosis/lookalikes.md): Many cannabis problems look alike in a photo. The ones growers confuse most are Ca vs Mg vs K, nitrogen toxicity vs overwatering claw, light bleaching vs Mg deficiency, spider-mite stippling vs calcium spots, heat vs light stress, Pythium vs low dissolved oxygen, Fe vs Mn, and nutrient burn vs K deficiency. Each pair separates on three things: where on the plant it started, the exact pattern, and one cheap test (a lens, a runoff EC reading, a root check, a light meter or a lifted pot). (Supported) - [Cannabis root problems: the master decision tree](https://genetixbay.com/knowledge/diagnosis/root-problems-decision-tree.md): Healthy cannabis roots are white to cream, firm and smell earthy or of nothing. Brown, slimy roots whose outer skin slides off and smell rotten are root rot (usually Pythium), driven by warm, oxygen-poor water or waterlogged media. Firm, odourless tan roots are usually stained, not sick. Check solution temperature (target 18–21 °C) and dissolved oxygen first, then texture and smell, then insects. Root problems show above ground as drooping with a wet root zone, yellowing and stunting. (Supported) - [Clawing leaves on cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/clawing-leaves.md): Leaves that curl down at the tips like a talon, especially if dark green and glossy, most often mean excess nitrogen and high EC, or a waterlogged, oxygen-starved root zone. Check watering and runoff EC first; distorted, crinkled clawing on new growth instead points to broad mites, calcium/boron problems or a viroid. (Grower practice) - [Drooping cannabis: overwatering vs underwatering](https://genetixbay.com/knowledge/diagnosis/drooping-overwatering-vs-underwatering.md): Lift the pot: a heavy pot with firm, swollen-looking drooping leaves is overwatered (roots short of oxygen); a light pot with limp, papery leaves is underwatered. If the medium is moist and the plant still wilts, especially one plant at a time or in hydro, suspect root rot or vascular wilt and look at the roots. (Supported) - [Foxtailing buds on cannabis: genetics or stress?](https://genetixbay.com/knowledge/diagnosis/foxtails.md): Foxtails (new calyx spires growing out of mature buds) are either a cultivar trait, which appears evenly through the canopy, or a stress response to heat and intense light, which shows mostly on the top colas nearest the fixture. Measure canopy leaf temperature and PPFD at the tops; evidence is mainly grower observation. (Grower practice) - [Hermaphrodite cannabis (bananas and nanners): what to do](https://genetixbay.com/knowledge/diagnosis/hermaphrodites.md): Hermaphroditic flowers are anthers (often banana-shaped) or pollen sacs forming on a female plant. Cannabis is a dioecious species, and a well-bred female should stay female; herm-prone plants are mainly the product of bad breeding (repeated selfing, careless feminising, untested 'pollen chucker' seed). Stress such as light leaks or heat reveals that weakness rather than causing it in sound genetics. Fix the environment, remove the plant if it sheds pollen, and never keep it as a mother or breed from it. (Supported) - [How to describe your plant's problem so it can be diagnosed](https://genetixbay.com/knowledge/diagnosis/how-to-describe-your-plants-problem.md): A plant problem can be diagnosed quickly only if the description says where on the plant it started (old or new growth), the exact pattern, how fast it is spreading, and the readings: pH and EC of input and runoff, temperature, RH, light intensity or distance, medium, system, water source, stage with the day count from the flip, and anything you changed in the last week. Add a whole-plant photo and a close-up of the top and underside of an affected leaf, taken in white light. (Grower practice) - [How to diagnose any cannabis plant problem](https://genetixbay.com/knowledge/diagnosis/how-to-diagnose-any-problem.md): Diagnose in a fixed order: confirm it is a real problem, note where on the plant it started (old vs new growth) and the pattern, then rule out root zone and pH, then environment and light, then pests and disease, and only then blame a nutrient. Change one thing at a time and judge the fix on new growth. (Supported) - [Purple or red stems and leaves on cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/purple-stems-leaves.md): Purple or red stems and petioles on a healthy, growing plant are usually genetics, cool nights or bright light, and need no fix. Treat it as a problem only when it comes with something else: lower-leaf yellowing (nitrogen), dark or bronzed spotting on old leaves (phosphorus), or slow growth with a cold or wet root zone. Check root-zone temperature and pH before adding phosphorus. (Supported) - [Purple, red, bronze or dark leaves on cannabis: the master discolouration decision tree](https://genetixbay.com/knowledge/diagnosis/discolouration-decision-tree.md): Most purple and red on a healthy, growing cannabis plant is anthocyanin: genetics, cool nights or strong light, and no fix is needed. Discolouration is a problem only alongside another sign: red-brown petioles with bottom-up yellowing (nitrogen), dull dark leaves with olive-bronze spots and slow growth (phosphorus uptake, often a cold or high-pH root zone), very dark glossy clawed leaves (nitrogen excess), bronze, brittle, upward-curling leaves (russet mites, or late Mg or K deficiency), or reds and oranges as leaves fade in late flower (normal senescence). (Supported) - [Rust-coloured spots on cannabis leaves: a differential](https://genetixbay.com/knowledge/diagnosis/rust-spots.md): Rusty brown spots are most often a calcium or phosphorus uptake problem driven by pH or root-zone stress, but leaf septoria (spots with yellow halos on lower leaves, spreading in humidity) and spider-mite stippling look similar. Check pH and root zone, then turn the leaf over with a hand lens, then decide between Ca, P, Mg/Mn and disease. (Supported) - [Slow or stunted cannabis growth: a differential](https://genetixbay.com/knowledge/diagnosis/slow-growth.md): When a plant just isn't growing, the cause is usually the root zone (overwatering, cold, small or rotting roots), too little light, or a cool room; nutrient shortages come later. Plants that stay stunted with small leaves and short internodes while neighbours thrive should be tested for hop latent viroid and checked for root aphids. (Supported) - [Spots, brown patches and dead edges on cannabis leaves: the master decision tree](https://genetixbay.com/knowledge/diagnosis/spots-necrosis-decision-tree.md): Cannabis leaf spots and dead tissue sort into four groups: pest feeding (pale stippling or silver scars, seen with a 10–20× lens under the leaf), disease (spots with yellow halos and tiny black dots, spreading from the bottom in humidity), nutrient or root-zone disorders (Ca, P, K, Mn, B, salts, in a pattern tied to leaf age) and physical damage (spray droplets, fans, heat, light). Flip the leaf first, then check runoff pH and EC, and only then pick a nutrient. (Supported) - [Stretchy, leggy cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/stretching.md): Long internodes and thin stems mean the plant is reaching for light: PPFD too low, light too far away, a low red-to-far-red ratio (shade or crowding), or warm days relative to nights. Some stretch in the first 2–3 weeks after the switch to 12/12 is normal and cultivar dependent. Measure PPFD and day/night temperatures before blaming genetics. (Supported) - [Taco or canoeing leaves on cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/taco-canoeing-leaves.md): Leaflets folding upward along the midrib (taco, canoe) on the top of the canopy are almost always heat or light stress, often with low humidity (high VPD). Measure leaf temperature, PPFD and RH at the canopy before anything else; if the whole plant is affected, check the root zone, then calcium and magnesium. (Supported) - [White or grey coating on cannabis: the master decision tree](https://genetixbay.com/knowledge/diagnosis/white-grey-coatings-decision-tree.md): A white or grey coating on cannabis is, in order of how often it matters: powdery mildew (flour-like patches that smear and return), spray or hard-water residue (follows the drip lines), trichomes (on buds and sugar leaves only), thrips silvering, spider-mite webbing, or grey Botrytis fuzz on buds and stems. On the medium, white fuzz is usually harmless mycelium and a hard crust is salt. A rub test and a 20–60x lens settle most cases in two minutes. (Supported) - [White powder or white spots on cannabis leaves: a differential](https://genetixbay.com/knowledge/diagnosis/white-powder-on-leaves.md): Flour-like circular white patches that smear off and come back are powdery mildew until proven otherwise. Rule out spray or hard-water residue (on the surfaces you sprayed, dries in drip lines), trichomes (on sugar leaves and buds, glassy under a lens), silvery thrips scarring and mite stippling. Confirm with a 20-60x lens before treating. (Supported) - [Why are my cannabis leaves curling? The master curling and clawing decision tree](https://genetixbay.com/knowledge/diagnosis/curling-clawing-decision-tree.md): Which way a cannabis leaf curls is the first clue. Edges folding up (taco, canoe) at the top of the canopy is heat, light or high VPD. Tips hooking down like a talon on dark, glossy leaves is excess nitrogen with high EC; whole leaves curling down and puffy on a heavy pot is overwatering. Twisted, crinkled, stunted new growth is broad or russet mites, calcium or boron delivery, a viroid, or growth-regulator herbicide drift. Leaves angled up and flat at lights-on ('praying') is healthy. (Supported) - [Why is my cannabis drooping or wilting? The master decision tree](https://genetixbay.com/knowledge/diagnosis/drooping-wilting-decision-tree.md): Drooping cannabis is diagnosed by one question: is the root zone wet or dry? A light, dry pot with limp leaves is underwatering; a heavy, wet pot with firm, curled-down leaves is overwatering. Wilting while the roots sit in water means the roots are failing: Pythium root rot, low dissolved oxygen, a hot reservoir, Fusarium wilt, or (in DWC and especially HPA) a failed pump, which is an emergency measured in minutes to hours. Transplant shock, unrooted clones, heat, stem damage and salt stress complete the list. (Supported) - [Why is my cannabis turning yellow? The master yellowing decision tree](https://genetixbay.com/knowledge/diagnosis/yellowing-decision-tree.md): Cannabis yellowing is diagnosed in four forks: where it started (old leaves = mobile N, Mg, K; new leaves = immobile Fe, S, Mn, Zn, Ca, B), the pattern (uniform, interveinal, margins, spots, bleached tops), the root-zone readings (pH, EC, moisture, root colour) and the stage. Most yellowing in practice is roots that cannot absorb (overwatering, cold, rot, pH out of range) rather than a missing nutrient; late-flower fade and top-only bleaching under strong light are not deficiencies. (Supported) - [Yellow new growth on cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/yellow-new-growth.md): Yellowing at the top of the plant points to an immobile nutrient (Fe, S, Mn, Zn, Cu, B, Ca) that the roots are failing to deliver, and the usual cause is high root-zone pH or a wet, cold or damaged root zone rather than a lack of fertiliser. Rule out light bleaching, broad/russet mites and viroid stunting before adding micronutrients. (Supported) - [Yellowing lower leaves on cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/yellowing-lower-leaves.md): Lower-leaf yellowing is usually nitrogen shortage or, far more often, roots that cannot take nitrogen up (overwatering, cold or rotting roots, pH out of range). Uniform yellow climbing from the bottom suggests N; green veins with yellow between them suggests Mg; yellow-then-brown margins suggest K. In late flower, gradual fade is normal. (Supported) ## Harvest and cure Ripeness, flushing evidence, drying, curing, storage. - [Curing and burping: jars, humidity and how long](https://genetixbay.com/knowledge/harvest-cure/curing-burping.md): Curing is a slow, steady decline in the bud's moisture content and water activity, not a constant hold: start around aw 0.62–0.65 and let it settle towards 0.55–0.58 over two to eight weeks, burping daily at first, then weekly. Jar RH is only a proxy for the bud, valid once a sealed jar has equilibrated (aw ≈ RH / 100). Check with the stem snap, an equilibrated hygrometer and weight. Humidity packs are a marketing gimmick; if a jar is too dry, add a fresh bud. (Grower practice) - [Drying cannabis: the 60/60 method and water activity](https://genetixbay.com/knowledge/harvest-cure/drying.md): Dry slowly and in the dark at about 15–21 °C (60–70 °F) and 55–62 % RH, the popular 60/60 target, for 7–14 days until small stems snap and buds reach a water activity of about 0.60–0.65. ASTM D8197 sets 0.55–0.65 aw as the range that protects against mould without making flower brittle. Judge the bud (stem snap, an equilibrated jar reading, weight), not the room. Wet vs dry trim is grower preference. Fast, warm drying loses volatile monoterpenes, and wet, still air grows mould. (Supported) - [Irradiated cannabis: gamma, e-beam, X-ray, ozone, RF and what they do to your weed](https://genetixbay.com/knowledge/harvest-cure/irradiated-cannabis.md): Much legal cannabis is decontaminated after harvest so it can pass microbial limits. That means ionising radiation (gamma from cobalt-60, electron beam, X-ray), or ozone, cold plasma, radio-frequency heating, UV or steam. Irradiation doesn't make flower radioactive. At typical doses (2.5–20 kGy) studies find no meaningful change in total THC or CBD. Effects on terpenes range from nothing measurable to 10–20 % losses of volatile monoterpenes, up to 38 % for one compound. Killing mould doesn't remove mycotoxins it has already made. Disclosure rules are patchy: Canada requires the irradiation symbol on edibles but not on dried flower, Washington discloses remediation to consumers only on request, and Nevada has a treatment-label rule. Most places tell the shopper nothing. Growing your own, where legal, with clean IPM and a proper dry avoids the issue. (Supported) - [Long-term storage: keeping cured flower potent and aromatic](https://genetixbay.com/knowledge/harvest-cure/long-term-storage.md): Light is the biggest single cause of cannabinoid loss in storage, air oxidation turns THC into CBN, and warmth and humidity speed both and invite mould. Store cured flower in full, airtight, opaque glass with the bud at aw 0.55–0.65 (an equilibrated jar reading), cool and dark; skip humidity packs, a marketing gimmick. Kept that way it is reasonably stable for one to two years; at room temperature over several years THC loss can be near total. Freezing is possible but makes trichomes brittle. (Supported) - [Pre-harvest flushing: a myth that costs you yield and resin](https://genetixbay.com/knowledge/harvest-cure/flush-debate.md): Pre-harvest flushing is a myth, and a harmful one. Starving the plant of nutrients in its last weeks takes food away during the phase when it is packing on most of its final weight, trichomes and resin, so it costs yield and resin and gives nothing back: controlled studies found no gain in flower quality, minerals or cannabinoids, and longer nutrient withdrawal tended to cut dry mass and cannabinoid yield. Cannabis stores what it takes up in its tissue, and plain water at the end does not wash it out. Feed through to harvest at stage-appropriate strength; taste and ash are made by plant health, not overfeeding, and slow drying and proper curing. The one valid flush treats the medium, not the plant: a root-zone flush to wash out accumulated salts, at any stage. (Myth) - [Trichome ripeness: clear, cloudy, amber, and what the evidence says](https://genetixbay.com/knowledge/harvest-cure/trichome-ripeness.md): Trichome heads go from clear to cloudy (milky) to amber or brown as flowers mature; research confirms browning marks gland senescence and that trichomes on one bract mature unevenly and at genotype-specific rates. Cannabinoid concentration typically rises to a plateau and then falls as plants senesce. The popular claim that amber heads mean high CBN and couch-lock is a myth: CBN mainly forms by oxidation after harvest. A dark period before harvest is a myth too. Harvest when most heads are cloudy with some amber, and track it by date and lab tests for your cultivar. (Grower practice) ## Breeding Genetics, pollination, selection, stabilisation, seed production. - [Backcrossing, IBLs and stabilisation](https://genetixbay.com/knowledge/breeding/backcrossing-ibl-stabilisation.md): A backcross crosses offspring back to one parent (the recurrent parent) to recover that parent's genome while keeping a trait from the other: each backcross halves the donor's share (50%, 25%, 12.5%, 6.25%...). An IBL is a line inbred and selected over many generations until it breeds fairly true. 'Stable' should mean measured uniformity across a grow-out, not a generation count. (Established) - [Breeder record-keeping and naming ethics](https://genetixbay.com/knowledge/breeding/record-keeping-naming-ethics.md): Keep a dated record of every plant, cross, batch and test, linked by permanent IDs, so any seed can be traced to its parents. Name lines honestly: a new, unique name for new genetics, the original name only for the original genetics, clear labels (F2, BX, S1, feminised), and never a famous name on something it isn't. Names are claims; records are the evidence. Sex stability is part of the ethics: cull herm-prone plants, never breed from them, and publish every batch's herm rate. (Supported) - [Breeders vs pollen chuckers: what real cannabis breeding looks like](https://genetixbay.com/knowledge/breeding/breeders-vs-pollen-chuckers.md): A breeder sets a goal, grows large populations, selects both females and males, progeny-tests the parents, stabilises the line over generations (F2s, backcrosses, IBLs), test-grows every batch and discloses its herm rate. A pollen chucker crosses two popular cuts, or selfs one, and sells the first-generation seed untested. Plant-breeding science explains why the difference shows up in your tent: crosses of heterozygous clones segregate, selecting only one sex halves progress, and intersex expression is heritable and responds to selection. (Supported) - [Breeding autoflowers: getting the trait into a photoperiod line](https://genetixbay.com/knowledge/breeding/breeding-autoflowers.md): Because autoflowering is recessive in mapped populations, a photo x auto F1 is all photoperiod. You recover autos in the F2 (about 1 in 4) or by backcrossing the F1 to the auto parent (about 1 in 2). To make an auto version of a photoperiod line, alternate crossing to the photo parent with a generation that reveals autos, or use a DNA marker to keep carriers. (Supported) - [Chemotype inheritance: how THC and CBD synthase alleles pass on](https://genetixbay.com/knowledge/breeding/chemotype-inheritance.md): Whether a plant is THC dominant, CBD dominant or mixed is controlled mainly by a single inheritance block carrying THCA synthase and CBDA synthase genes, which behaves close to codominant: THC x CBD gives mixed (type II) F1s and a 1:2:1 split in the F2. CBG-dominant and cannabinoid-free types come from non-functional synthase alleles. Total cannabinoid amount is a separate, quantitative trait. (Established) - [Clone-only cuts and how to preserve them](https://genetixbay.com/knowledge/breeding/clone-only-preservation.md): A clone-only is one selected genotype kept alive by cuttings. It can be lost to pests, disease, hop latent viroid (HLVd) or accident, and it accumulates rare somatic mutations, which are not the same thing as a loss. Cuts from different parts of a plant can also behave differently (topophysis), so take them from consistent locations. Preserve it with clean, tested mothers in at least two locations, regular fresh cuttings, a tissue-culture backup where possible, and seed (S1s or crosses) as genetic insurance, not as a copy. (Supported) - [Collecting and storing cannabis pollen](https://genetixbay.com/knowledge/breeding/pollen-collection-storage.md): Collect pollen from freshly opened sacs in still, clean air, sieve it, dry it briefly, and use it within days, or mix it with a dry carrier (baked flour), seal it with desiccant and freeze it. Cannabis pollen loses viability within about a week in a fridge; one study kept it viable for at least four months by mixing it 1:10 with baked flour, vacuum-drying and storing in liquid nitrogen. Home freezer storage is grower practice and should be germination tested. (Supported) - [Elite clone-only gatekeeping: why the classics live in a few hands](https://genetixbay.com/knowledge/breeding/elite-clone-gatekeeping.md): Many celebrated cultivars, from the Chem 91 and original OG Kush cuts to Pre-'98 Bubba Kush and old Skunk phenotypes, began as single plants and spread as cuttings through small circles. Published histories describe cuts passed only between friends, press reports put rare clone-only cuts at US$10,000 or more, and the classic Skunk aroma is described by veterans as gone from today's seed. The founder's view is that some holders keep cuts closed on purpose to control the gene pool. The public record documents the scarcity and the closed circles but can't show motive. A single garden is also a single point of failure: one HLVd infection or one bad summer can erase a cut. GenetixBay's answer is open preservation: GB-IDs, the Stud Book, preservation rewards and sharing in legal lanes. (Grower practice) - [F1, F2, F3 explained: what filial generations really mean](https://genetixbay.com/knowledge/breeding/f1-f2-f3-explained.md): An F1 is the first generation from two parents; it is uniform only if both parents were true-breeding (inbred). An F2 comes from crossing F1 siblings and shows the most variation. Each later generation of sib-mating with selection increases uniformity slowly. In cannabis, most 'F1 hybrids' are crosses of heterozygous clones, so they behave like segregating F2s. (Established) - [Feminised seed and sex reversal: methods, with safety notes](https://genetixbay.com/knowledge/breeding/feminised-seed-sex-reversal.md): Feminised seed is made by forcing a genetic female to grow male flowers, then using that pollen on another (or the same) female. Silver ions block ethylene action; silver thiosulfate (STS) sprayed at about 3 mM silver was the most effective treatment in a controlled hemp study, and colloidal silver also works. Silver compounds are hazardous: wear gloves and eye protection, never consume treated plants, and dispose of waste as hazardous. Careless feminising (unproven donors, stress-herm pollen) is a main source of herm-prone seed; reverse only females proven stable over at least two runs. (Established) - [Genotyping: what a DNA test can and can't prove](https://genetixbay.com/knowledge/breeding/genotyping-what-tests-prove.md): A DNA test can reliably show whether two samples are the same genotype, rule out a claimed parent (exclusion), support a parent-child relationship when both parents are sampled, predict sex and chemotype class from seedlings, and place a plant on a map of genetic groups. It cannot prove a 40-year-old pedigree from a name, measure THC %, tell you a plant's 'indica percentage', or guarantee how it will grow. (Supported) - [How to document lineage evidence (GB-ID evidence levels L0-L4)](https://genetixbay.com/knowledge/breeding/documenting-lineage-evidence.md): On GenetixBay every parentage statement is a claim with an evidence level: L0 unverified, L1 community reported with a source, L2 breeder reported, L3 documented by an accepted GB-DOC, L4 lab-confirmed by a genomic report consistent with the parent-child relationship. Breeders raise the level by attaching dated, original evidence and, where possible, by recording crosses on the platform as they happen. (Supported) - [Inbreeding depression and hybrid vigour](https://genetixbay.com/knowledge/breeding/inbreeding-depression-hybrid-vigour.md): Inbreeding makes hidden harmful recessive alleles homozygous, so inbred plants often lose vigour, yield and fertility (inbreeding depression). Crossing unrelated lines masks those alleles and can push F1s above both parents (hybrid vigour, or heterosis). The vigour fades in the F2 because the masking breaks down as genes segregate. (Established) - [Mendelian genetics for growers, with Punnett squares](https://genetixbay.com/knowledge/breeding/mendelian-genetics-for-growers.md): Traits controlled by one gene follow Mendel's rules: each parent passes one of its two alleles at random, so a cross of two heterozygotes gives a 1:2:1 genotype ratio and, for a dominant trait, a 3:1 look. In cannabis the clearest single-gene examples are autoflowering (recessive) and the THC/CBD chemotype switch (close to codominant). (Established) - [Pollination and seed production, step by step](https://genetixbay.com/knowledge/breeding/pollination-seed-production.md): Pollinate females about 2-4 weeks into flower when stigmas are white and receptive, using fresh or stored pollen applied with a brush or bag to marked branches; seeds mature in roughly 5-7 weeks. Isolation is everything: pollen travels on air, clothing and fans, so a planned cross needs a separate space or strict bagging, and every pollination gets a dated record. (Supported) - [Polyhybrids vs landraces: what each gives a breeder](https://genetixbay.com/knowledge/breeding/polyhybrids-vs-landraces.md): A landrace is a locally adapted, farmer-maintained population with a regional history; it is variable but coherent, and a reservoir of diversity. A polyhybrid is a modern line with many ancestors from different gene pools; it can be highly productive but is heterozygous and segregates unpredictably. Breeders use landraces as sources of new traits and polyhybrids as elite starting material. (Supported) - [Quantitative traits and heritability: why most good traits are hard to fix](https://genetixbay.com/knowledge/breeding/quantitative-traits-heritability.md): Yield, potency, terpene totals, vigour and flowering time are controlled by many genes plus environment. Heritability (the share of variation due to genes in a given population and setting) predicts how much of a selected plant's advantage passes to its offspring: response = heritability x selection differential. Cannabinoid ratios are highly heritable; absolute THC % and yield much less so. (Established) - [S1s and selfing: what happens when a plant pollinates itself](https://genetixbay.com/knowledge/breeding/s1-selfing.md): An S1 is seed from a plant pollinated by its own pollen, usually by reversing one female clone or branch. S1s are feminised, and they are not copies of the parent: each S1 seed is a new genotype. Selfing halves heterozygosity per generation, reveals hidden recessives (good and bad), and is a fast way to test what a clone carries. Done carelessly, especially S1 on S1 from plants that herm, it is one of the main ways herm-prone lines are made; only self proven-stable females and cull every intersex offspring. (Established) - [Seed germination testing and quality control for breeders](https://genetixbay.com/knowledge/breeding/seed-germination-testing-qc.md): Before seed leaves your hands, test it: germinate a random sample of at least 100 seeds (400 in four replicates is the lab standard) and count normal seedlings, not just cracked seeds. Report the result with the date on the batch record. Store seed cool and dry; one study recommended about 5 °C to keep germination for years. (Supported) - [Selection and pheno hunting: sample sizes and scoring rubrics](https://genetixbay.com/knowledge/breeding/selection-pheno-hunting.md): A pheno hunt is a selection experiment: grow enough seeds to have a real chance of finding what you want, clone every candidate before flowering, score each plant on a fixed weighted rubric, and re-grow the top few as clones before you call a keeper. The plants needed follow 1 - (1 - p)^n: a 1-in-10 type needs 29 plants for a 95% chance of seeing at least one. Sex stability is a gate: any plant that herms is culled, whatever else it scores. (Supported) - [Tissue culture basics for cannabis growers and breeders](https://genetixbay.com/knowledge/breeding/tissue-culture-basics.md): Tissue culture grows small pieces of a plant (usually nodes or shoot tips) on a sterile gel medium, giving clean, compact, long-lived backups of clones and a route to cleaning up infected stock. Cannabis tissue culture works but is genotype dependent and poorly replicated in the literature; contamination control is the main skill. (Supported) ## Genetics history Landraces, heritage lines and lineages, with evidence labels. - [Craft vs industrial cannabis: did legalisation's commercial model hurt quality?](https://genetixbay.com/knowledge/genetics-history/craft-vs-industrial-cannabis.md): The founder's opinion is that legalisation's commercial model hurt quality: small, careful growers were priced out by large facilities, and product is now grown to a price. The evidence supports parts of that. Wholesale prices fell by roughly 75-80 %, Oregon's flower is at its lowest price since legalisation, Washington lost about a third of its producer businesses from 2017 to 2023, California's licensed canopy is dominated by a few large farms, Canadian excise duty can take 30 % or more of a producer's gross revenue, and regulators have recalled legal product for mould and pesticides. But no data show the grey market was cleaner, and Health Canada's own testing found illegal flower far dirtier than legal flower. Craft vs industrial is the real fault line. Growing your own, where legal, is the surest way to control quality. (Contested) - [How hybrid 'strains' emerged](https://genetixbay.com/knowledge/genetics-history/how-hybrid-strains-emerged.md): Modern drug-type cannabis is mostly a mix of South Asian-derived long-flowering types and Central Asian (Afghan) hashish types, crossed from the 1970s onwards in North America, then distributed by Dutch seed companies from the mid-1980s, and multiplied into thousands of names in clone-driven and legal markets since the 1990s. The broad story is supported by genetics; most specific pedigrees are oral claims with conflicting versions. (Contested) - [Indica, sativa and ruderalis: what the names really mean](https://genetixbay.com/knowledge/genetics-history/indica-sativa-ruderalis.md): Cannabis is one species, Cannabis sativa L., showing different phenotypes. Nearly everything grown today is a hybrid, with a few outlier landraces. Distinct groups, ruderalis included, may have existed long ago, but not today. As a guide to effects or species, indica vs sativa is nonsense: genetic and chemical studies show the labels don't match ancestry or predict chemistry. At most they describe plant shape: leaflet width, structure and flowering time. (Supported) - [Landrace hunting or biopiracy? Benefit-sharing, consent and cannabis](https://genetixbay.com/knowledge/genetics-history/landrace-hunting-and-biopiracy.md): International law says a country owns rights over its genetic resources: under the Convention on Biological Diversity (1992) and the Nagoya Protocol (in force 2014), anyone taking plant material for breeding or research needs prior informed consent and mutually agreed terms, including benefit-sharing. Cannabis falls through the cracks: it isn't in the Plant Treaty's crop list, it's still a Schedule I drug under the 1961 Single Convention, most seed was collected before these rules existed, and the US and Canada aren't Nagoya parties. Turmeric, neem, hoodia and rooibos show what credit and compensation look like when they're taken seriously. GenetixBay's position: credit the source region and community on every record, document provenance honestly with evidence levels, encourage benefit-sharing and fair practice, and reward returning value to source communities. (Supported) - [Landraces of the world: an overview](https://genetixbay.com/knowledge/genetics-history/landraces-of-the-world.md): Drug-type cannabis landraces developed across South and Central Asia and were carried to Africa, the Middle East and the Americas, where local farmers adapted them over centuries. Genomic work points to an Asian origin of domestication (exact region contested). Many traditional landraces are now endangered by hybrid replacement, and most 'landrace' seed in commerce is better described as heirloom: collected at some point, then maintained elsewhere. Every origin story here is a claim; this article labels the evidence. (Supported) - [Old cannabis wasn't weak: the "so much stronger than 20 years ago" myth](https://genetixbay.com/knowledge/genetics-history/old-cannabis-was-not-weak.md): "Cannabis is far stronger than it used to be" is false as a claim about the plant's genetics. Famous hashish, charas and sinsemilla traditions are centuries old and impossible with 5 % plants, and old seed grown well today still tests high. The 'weak old weed' numbers come from seized samples: mostly cheap compressed export brick of leaf, seed and stem, often stored for years before testing, measured with changing methods. The best of what source regions grew was rarely exported. What changed is the market and growing technique: fresh, seedless, indoor flower. (Myth) - [Patents and the gene pool: who can own a cannabis plant?](https://genetixbay.com/knowledge/genetics-history/patents-and-the-gene-pool.md): Cannabis can be protected by US utility patents (covering plants, traits, extracts and methods), plant patents (for asexually reproduced varieties) and plant variety protection certificates (for seed-propagated hemp, since 2019), plus plant breeders' rights in Canada and the EU. Grants are public record. Legal commentators worry that thin prior art and broad claims could fence off parts of a shared gene pool. The open responses are public, dated documentation: prior-art databases, open-source seed pledges and genotype registries. GenetixBay's answer is preservation, GB-ID documentation and open sharing. (Supported) - [Same cut, a thousand names: renaming, relabelling and the shrinking gene pool](https://genetixbay.com/knowledge/genetics-history/same-cut-a-thousand-names.md): Renaming clones, relabelling cuts and reusing famous names make the market look far more diverse than it is. Genetic studies find the same plant sold under different names and different plants sold under one name: in one study 35 % of comparisons put a sample closer to a differently named sample than to its namesakes, and in Nevada 637 recorded names (396 after cleaning) covered three chemical profiles. Hidden sameness makes breeders cross near-identical material while believing they're adding diversity. GenetixBay's answer is the GB-ID: a permanent record tied to the plant, its source and its evidence, not to its name. (Supported) - [Why everything tastes the same: the evidence that commercial cannabis is converging](https://genetixbay.com/knowledge/genetics-history/why-everything-tastes-the-same.md): Growers keep saying modern weed all tastes the same, and the data back them up. A study of nearly 90,000 US lab results found THC-dominant flower falling into just three terpene groups, two of which held about 87 % of samples. Strain names and indica/sativa labels promise far more variety than the chemistry shows, traditional landraces in their home regions are being replaced by introduced hybrids, and retail prices rise with THC rather than aroma. GenetixBay's answer is preservation, documentation with GB-IDs, and open sharing of distinctive lines. (Supported) - [Why strain names are unreliable: what genetic studies show](https://genetixbay.com/knowledge/genetics-history/why-strain-names-are-unreliable.md): Several genetic and chemical studies of retail cannabis show that the same strain name often hides different genotypes, that 'indica' and 'sativa' labels don't match genome-wide ancestry, and that potency labels vary by lab. Some names are reasonably consistent, many are not. A name is a claim; a documented source, a GB-ID with evidence and, ultimately, DNA are the evidence. (Supported) ## Symptom checker Describe what you see, answer a few questions, get the likely cause, the test that confirms it and the fix. Interactive: https://genetixbay.com/knowledge/diagnose/ · Graph (symptoms, causes, questions, tests): https://genetixbay.com/knowledge/api/diagnosis.json. Guidance, not a guarantee: confirm with the tests. - [Lower (older) leaves turning evenly yellow](https://genetixbay.com/knowledge/diagnose/yellow-lower-leaves.md): likely causes Nitrogen deficiency, Normal late-flower fade (senescence), Overwatering (roots short of air) - [Whole plant pale or lime green](https://genetixbay.com/knowledge/diagnose/whole-plant-pale.md): likely causes General underfeeding (whole feed too weak), Nitrogen deficiency, Overwatering (roots short of air) - [Yellow between the veins on older leaves, veins stay green](https://genetixbay.com/knowledge/diagnose/interveinal-yellow-old.md): likely causes Magnesium deficiency, Low root-zone pH starving calcium and magnesium, Unbuffered or new coco pulling calcium and magnesium - [Yellow edges and leaf teeth on older leaves](https://genetixbay.com/knowledge/diagnose/yellow-margins-old.md): likely causes Potassium deficiency, Manganese toxicity (usually low pH), Salt build-up in the root zone - [New growth evenly pale or yellow](https://genetixbay.com/knowledge/diagnose/yellow-new-growth.md): likely causes High root-zone pH locking out iron, manganese, zinc, boron and copper, Aphids, Sulfur deficiency - [Yellow between the veins on the newest leaves, veins green](https://genetixbay.com/knowledge/diagnose/interveinal-yellow-new.md): likely causes High root-zone pH locking out iron, manganese, zinc, boron and copper, Hard, alkaline water pushing pH up over weeks, Uncalibrated or failing pH or EC meter - [Netted yellowing on upper and middle leaves with small tan specks](https://genetixbay.com/knowledge/diagnose/netted-yellow-upper-spots.md): likely causes High root-zone pH locking out iron, manganese, zinc, boron and copper, Manganese deficiency - [New leaves almost white](https://genetixbay.com/knowledge/diagnose/white-new-growth.md): likely causes Light bleaching at the canopy top, High root-zone pH locking out iron, manganese, zinc, boron and copper, Iron deficiency (usually high pH) - [Yellow then tan edges on new leaves](https://genetixbay.com/knowledge/diagnose/yellow-new-margins.md): likely causes High root-zone pH locking out iron, manganese, zinc, boron and copper, Calcium deficiency (often a delivery problem), Zinc deficiency - [Top leaves or bracts bleached white or yellow nearest the light](https://genetixbay.com/knowledge/diagnose/bleached-top-leaves.md): likely causes Light bleaching at the canopy top, Heat or light stress foxtailing on the top colas, Light burn: too much light for the plant's climate and CO2 - [Middle leaves yellowing first](https://genetixbay.com/knowledge/diagnose/yellow-middle-leaves.md): likely causes Sulfur deficiency, Molybdenum deficiency, Very low pH limiting molybdenum - [Mottled mosaic or yellow streaks, distorted leaves](https://genetixbay.com/knowledge/diagnose/mosaic-mottle.md): likely causes Plant virus (e.g. beet curly top, lettuce chlorosis virus), Hop latent viroid (dudding), Herbicide drift or residue - [Fan leaves yellowing late in flower while buds keep ripening](https://genetixbay.com/knowledge/diagnose/late-flower-fade.md): likely causes Normal late-flower fade (senescence) - [Sudden yellowing across the plant within days](https://genetixbay.com/knowledge/diagnose/sudden-yellowing.md): likely causes Root rot (Pythium), Low dissolved oxygen in the root zone - [Seedling leaves (cotyledons) yellowing](https://genetixbay.com/knowledge/diagnose/yellow-cotyledons.md): likely causes Seed leaves yellowing as true leaves take over (normal), Overwatering (roots short of air), Nitrogen deficiency - [Damage only on one side of the plant or one area of the room](https://genetixbay.com/knowledge/diagnose/damage-one-side.md): likely causes Wind burn from a fan blowing directly on leaves, Physical damage (kinks, splits, broken branches), Fusarium wilt or crown rot - [Rust-brown spots on newer and middle leaves](https://genetixbay.com/knowledge/diagnose/rust-spots-new.md): likely causes Calcium deficiency (often a delivery problem), Low root-zone pH starving calcium and magnesium, Unbuffered or new coco pulling calcium and magnesium - [Dark olive or brown sunken spots on older leaves](https://genetixbay.com/knowledge/diagnose/olive-spots-old.md): likely causes Phosphorus deficiency, High pH reducing phosphorus availability - [Round brown spots with yellow halos on lower leaves](https://genetixbay.com/knowledge/diagnose/spots-yellow-halo.md): likely causes Septoria leaf spot - [Tan, crispy scorched edges on older leaves](https://genetixbay.com/knowledge/diagnose/scorched-margins-old.md): likely causes Potassium deficiency, Nutrient burn (feed too strong), Ammonium toxicity (too much NH4 in the feed) - [Brown, burnt leaf tips](https://genetixbay.com/knowledge/diagnose/burnt-tips.md): likely causes Nutrient burn (feed too strong), Salt build-up in the root zone, Sodium build-up (softened water, coco, recirculation) - [Small tan dead specks between veins on upper leaves](https://genetixbay.com/knowledge/diagnose/tan-specks-upper.md): likely causes Manganese deficiency - [Brown or dark speckling and bronzing on older leaves](https://genetixbay.com/knowledge/diagnose/brown-speckles-old.md): likely causes Manganese toxicity (usually low pH), Low root-zone pH starving calcium and magnesium, Iron and manganese excess at very low pH - [Irregular dead or bleached patches after spraying](https://genetixbay.com/knowledge/diagnose/random-dead-patches.md): likely causes Spray or foliar burn (pesticide, oil, soap, foliar feed) - [Crispy, papery or scorched top leaves](https://genetixbay.com/knowledge/diagnose/crispy-top-leaves.md): likely causes Heat stress, Light burn: too much light for the plant's climate and CO2, Air too dry / VPD too high - [Dry, torn or curled leaves facing a fan](https://genetixbay.com/knowledge/diagnose/wind-burn.md): likely causes Wind burn from a fan blowing directly on leaves - [Lower leaves dying and dropping quickly](https://genetixbay.com/knowledge/diagnose/lower-leaves-dying-fast.md): likely causes Nitrogen deficiency, Shaded lower leaves dying back (normal), Septoria leaf spot - [Dark, water-soaked lesions on leaves or stems](https://genetixbay.com/knowledge/diagnose/water-soaked-lesions.md): likely causes Botrytis bud rot (grey mould), Humidity too high / VPD too low - [Small raised blisters or corky bumps on leaf undersides](https://genetixbay.com/knowledge/diagnose/oedema-bumps.md): likely causes Humidity too high / VPD too low, Overwatering (roots short of air), Oedema (water uptake outrunning transpiration) - [Dark brown lesions on sugar leaves in flower](https://genetixbay.com/knowledge/diagnose/dark-lesions-sugar-leaves.md): likely causes Potassium deficiency - [Holes chewed in leaves or ragged edges](https://genetixbay.com/knowledge/diagnose/holes-in-leaves.md): likely causes Caterpillars and budworms - [Dark green, glossy leaves with tips hooking down (the claw)](https://genetixbay.com/knowledge/diagnose/clawing-dark.md): likely causes Nutrient burn (feed too strong), Too much nitrogen, Overwatering (roots short of air) - [Leaves curling down and limp while the pot is wet](https://genetixbay.com/knowledge/diagnose/curl-down-wet.md): likely causes Overwatering (roots short of air), Humidity too high / VPD too low, Oedema (water uptake outrunning transpiration) - [Leaves folding up along the midrib (taco)](https://genetixbay.com/knowledge/diagnose/taco-leaves.md): likely causes Heat stress, Light burn: too much light for the plant's climate and CO2, Air too dry / VPD too high - [Leaf edges curling up (canoeing)](https://genetixbay.com/knowledge/diagnose/canoe-edges-up.md): likely causes Heat stress, Air too dry / VPD too high, Light burn: too much light for the plant's climate and CO2 - [Leaves held upward, praying, healthy colour](https://genetixbay.com/knowledge/diagnose/praying-leaves.md): likely causes Normal leaf movement (praying by day, drooping at night) - [Twisted, distorted or crinkled new growth](https://genetixbay.com/knowledge/diagnose/twisted-new-growth.md): likely causes Calcium deficiency (often a delivery problem), Broad mites, Aphids - [Glossy, stiff, curled growing tips that stop growing](https://genetixbay.com/knowledge/diagnose/glossy-hardened-tips.md): likely causes Broad mites - [Growing tips dying or aborting](https://genetixbay.com/knowledge/diagnose/dying-growing-tips.md): likely causes Calcium deficiency (often a delivery problem), Boron deficiency, Broad mites - [Small, narrow or cupped new leaves](https://genetixbay.com/knowledge/diagnose/small-narrow-new-leaves.md): likely causes Calcium deficiency (often a delivery problem), High root-zone pH locking out iron, manganese, zinc, boron and copper, Broad mites - [Single-bladed, round or smooth-edged new leaves](https://genetixbay.com/knowledge/diagnose/single-blade-leaves.md): likely causes Light leak or interrupted dark period, Re-vegetation from too-long days in flower - [Leaf edges rolling under, leaves curling downward without darkening](https://genetixbay.com/knowledge/diagnose/margins-roll-under.md): likely causes Heat stress, Calcium deficiency (often a delivery problem), CO2 set far too high - [Drooping while the pot is heavy and wet](https://genetixbay.com/knowledge/diagnose/droop-wet-pot.md): likely causes Overwatering (roots short of air) - [Wilting with a light, dry pot](https://genetixbay.com/knowledge/diagnose/wilt-dry-pot.md): likely causes Underwatering, Dry, water-repellent medium (water runs straight through) - [Wilting even though the root zone is moist, not recovering overnight](https://genetixbay.com/knowledge/diagnose/wilt-moist-not-recovering.md): likely causes Root rot (Pythium), Low dissolved oxygen in the root zone, Reservoir or root zone too warm - [Sudden collapse of a hydro or aero plant within hours](https://genetixbay.com/knowledge/diagnose/sudden-collapse-hydro.md): likely causes Pump, timer, air or emitter failure in a hydro, aero or drip system - [Wilting under the lights that recovers at lights-off](https://genetixbay.com/knowledge/diagnose/midday-wilt.md): likely causes Heat stress, Air too dry / VPD too high, Low dissolved oxygen in the root zone - [A single branch wilting or dying](https://genetixbay.com/knowledge/diagnose/branch-wilt.md): likely causes Physical damage (kinks, splits, broken branches), Fusarium wilt or crown rot - [Seedling stem pinched and collapsing at the soil line](https://genetixbay.com/knowledge/diagnose/damping-off.md): likely causes Damping-off, Fungus gnats, Root rot (Pythium) - [Cuttings wilting](https://genetixbay.com/knowledge/diagnose/clone-wilting.md): likely causes Cuttings losing water faster than they can root, Air too dry / VPD too high, Fungus gnats - [Drooping or stall right after transplanting](https://genetixbay.com/knowledge/diagnose/droop-after-transplant.md): likely causes Transplant shock, Recovery stall after topping, supercropping or heavy defoliation - [Leaves droop at lights-off and lift in the morning](https://genetixbay.com/knowledge/diagnose/night-droop.md): likely causes Normal leaf movement (praying by day, drooping at night) - [Weak, floppy stems that can't hold the plant up](https://genetixbay.com/knowledge/diagnose/weak-stems.md): likely causes Not enough light, General underfeeding (whole feed too weak), Too much nitrogen - [Kinked, split or snapped stem](https://genetixbay.com/knowledge/diagnose/stem-damage.md): likely causes Physical damage (kinks, splits, broken branches) - [Brown, soft or sunken stem base or crown](https://genetixbay.com/knowledge/diagnose/stem-base-rot.md): likely causes Fusarium wilt or crown rot, Root rot (Pythium) - [Brown streaks inside the stem when cut](https://genetixbay.com/knowledge/diagnose/stem-internal-browning.md): likely causes Fusarium wilt or crown rot - [Lesions or grey mould on stems](https://genetixbay.com/knowledge/diagnose/stem-cankers.md): likely causes Botrytis bud rot (grey mould) - [Brittle stems that snap easily](https://genetixbay.com/knowledge/diagnose/brittle-stems.md): likely causes Hop latent viroid (dudding), Hemp russet mites - [Purple or red stems and petioles](https://genetixbay.com/knowledge/diagnose/purple-stems.md): likely causes Genetic purple colour (anthocyanin), Cold stress, Cold root zone (below about 16 °C / 61 °F) - [Red-purple petioles with yellowing lower leaves](https://genetixbay.com/knowledge/diagnose/red-petioles-yellow-lower.md): likely causes Nitrogen deficiency, Normal late-flower fade (senescence) - [Purple leaves, bracts or sugar leaves](https://genetixbay.com/knowledge/diagnose/purple-leaves.md): likely causes Genetic purple colour (anthocyanin), Normal late-flower fade (senescence), Cold stress - [Very dark green, glossy leaves](https://genetixbay.com/knowledge/diagnose/dark-green-leaves.md): likely causes Nutrient burn (feed too strong), Too much nitrogen, Cal-Mag overuse (excess calcium and nitrogen) - [Dark, dull blue-green leaves with purple or bronze blotches](https://genetixbay.com/knowledge/diagnose/dark-dull-purple-blotch.md): likely causes Cold stress, High pH reducing phosphorus availability, Phosphorus deficiency - [Bronzed, rusty-looking leaf surfaces](https://genetixbay.com/knowledge/diagnose/bronze-leaves.md): likely causes Hemp russet mites, Twospotted spider mites, Broad mites - [Dull, grey-green, leathery leaves](https://genetixbay.com/knowledge/diagnose/dull-grey-leaves.md): likely causes Sodium build-up (softened water, coco, recirculation), Salt build-up in the root zone, Chloride excess (salinity) - [Purple or dark buds in late flower](https://genetixbay.com/knowledge/diagnose/purple-buds.md): likely causes Genetic purple colour (anthocyanin) - [White powdery spots that wipe off and come back](https://genetixbay.com/knowledge/diagnose/white-powder.md): likely causes Powdery mildew, Humidity too high / VPD too low - [Grey, fuzzy mould](https://genetixbay.com/knowledge/diagnose/grey-fuzz.md): likely causes Botrytis bud rot (grey mould), Humidity too high / VPD too low - [White crust or residue that wipes off and stays gone](https://genetixbay.com/knowledge/diagnose/white-residue.md): likely causes Hard-water or spray residue, Spray or foliar burn (pesticide, oil, soap, foliar feed), Hard, alkaline water pushing pH up over weeks - [Sticky, shiny leaves (honeydew)](https://genetixbay.com/knowledge/diagnose/sticky-honeydew.md): likely causes Aphids, Whiteflies, Mealybugs - [Black sooty coating on leaves](https://genetixbay.com/knowledge/diagnose/sooty-mould.md): likely causes Whiteflies, Aphids, Mealybugs - [White cottony or waxy clumps in leaf axils and stems](https://genetixbay.com/knowledge/diagnose/white-cottony-clumps.md): likely causes Mealybugs - [White fuzz or threads on the medium surface](https://genetixbay.com/knowledge/diagnose/white-fuzz-medium.md): likely causes Harmless white fungus (mycelium) on organic medium - [White crust on the medium surface or pot edges](https://genetixbay.com/knowledge/diagnose/salt-crust-medium.md): likely causes Salt build-up in the root zone, Hard, alkaline water pushing pH up over weeks - [Green slime or algae on the medium, roots or in the reservoir](https://genetixbay.com/knowledge/diagnose/green-slime.md): likely causes Algae from light reaching wet surfaces or the reservoir - [Yellow patches on top of leaves with grey-purple fuzz underneath](https://genetixbay.com/knowledge/diagnose/fuzzy-underside-yellow-top.md): likely causes Downy mildew - [White crystals or sparkles on leaves and buds that don't wipe off](https://genetixbay.com/knowledge/diagnose/white-sparkle-trichomes.md): likely causes Trichomes or harmless features mistaken for a problem, Thrips - [Single yellow or brown sugar leaf on an otherwise green cola](https://genetixbay.com/knowledge/diagnose/bud-rot-dead-leaf.md): likely causes Botrytis bud rot (grey mould) - [Brown, mushy or grey tissue inside buds](https://genetixbay.com/knowledge/diagnose/bud-brown-inside.md): likely causes Botrytis bud rot (grey mould), Caterpillars and budworms - [White powder on buds and sugar leaves](https://genetixbay.com/knowledge/diagnose/powder-on-buds.md): likely causes Powdery mildew - [Foxtails: new calyx spires growing out of mature buds](https://genetixbay.com/knowledge/diagnose/foxtails.md): likely causes Heat or light stress foxtailing on the top colas, Heat stress, Cultivar foxtailing (genetic) - [Yellow banana-shaped anthers in the buds](https://genetixbay.com/knowledge/diagnose/nanners.md): likely causes Hermaphrodite (herm-prone genetics revealed by stress), Light leak or interrupted dark period, Heat stress - [Pollen sacs (balls) at nodes of a female plant](https://genetixbay.com/knowledge/diagnose/pollen-sacs.md): likely causes Hermaphrodite (herm-prone genetics revealed by stress), Light leak or interrupted dark period - [Seeds in the buds](https://genetixbay.com/knowledge/diagnose/seeds-in-buds.md): likely causes Hermaphrodite (herm-prone genetics revealed by stress) - [Airy, loose, larfy buds](https://genetixbay.com/knowledge/diagnose/airy-buds.md): likely causes Hop latent viroid (dudding), Not enough light, Heat stress - [Pistils browning early in flower](https://genetixbay.com/knowledge/diagnose/pistils-brown-early.md): likely causes Heat stress, Heat or light stress foxtailing on the top colas, Light bleaching at the canopy top - [Droppings (frass), webbing or holes in buds](https://genetixbay.com/knowledge/diagnose/frass-in-buds.md): likely causes Caterpillars and budworms - [Flowering not starting or very slow after the flip](https://genetixbay.com/knowledge/diagnose/flowering-delayed.md): likely causes Light leak or interrupted dark period, Long-flowering or light-sensitive cultivar - [Bud swell stalls in mid-late flower](https://genetixbay.com/knowledge/diagnose/buds-stall.md): likely causes Nitrogen deficiency, Re-vegetation from too-long days in flower, Potassium deficiency - [Musty, mouldy smell in the canopy](https://genetixbay.com/knowledge/diagnose/musty-smell.md): likely causes Botrytis bud rot (grey mould), Humidity too high / VPD too low - [Brown, slimy roots; outer layer slides off](https://genetixbay.com/knowledge/diagnose/roots-brown-slimy.md): likely causes Root rot (Pythium), Reservoir or root zone too warm, Low dissolved oxygen in the root zone - [Tan or tea-stained roots that are still firm](https://genetixbay.com/knowledge/diagnose/roots-stained-firm.md): likely causes Harmless root staining (nutrients, tannins, additives), Ammonium toxicity (too much NH4 in the feed) - [Rotten, sour or sewer smell from roots, medium or reservoir](https://genetixbay.com/knowledge/diagnose/root-zone-smell.md): likely causes Low dissolved oxygen in the root zone, Reservoir or root zone too warm, Root rot (Pythium) - [Thick mat of circling roots at the pot wall](https://genetixbay.com/knowledge/diagnose/roots-circling.md): likely causes Root-bound in a pot too small - [No fresh white root tips](https://genetixbay.com/knowledge/diagnose/no-new-root-tips.md): likely causes Low dissolved oxygen in the root zone, Chlorine or chloramine in tap water harming roots and soil life, Pump, timer, air or emitter failure in a hydro, aero or drip system - [Short, stubby, brown root tips](https://genetixbay.com/knowledge/diagnose/stubby-root-tips.md): likely causes Nutrient burn (feed too strong), Salt build-up in the root zone, Copper toxicity (copper sprays, ionisers, pipework) - [White waxy residue and tiny insects on roots](https://genetixbay.com/knowledge/diagnose/root-aphids.md): likely causes Root aphids, Mealybugs - [Tiny clear larvae with black heads in the medium](https://genetixbay.com/knowledge/diagnose/larvae-in-medium.md): likely causes Fungus gnats, Overwatering (roots short of air) - [Small black flies around the medium](https://genetixbay.com/knowledge/diagnose/gnats-flying.md): likely causes Fungus gnats, Overwatering (roots short of air), Algae from light reaching wet surfaces or the reservoir - [Reservoir or root zone water warm (above 23 °C / 73 °F)](https://genetixbay.com/knowledge/diagnose/reservoir-warm.md): likely causes Reservoir or root zone too warm, Pump, timer, air or emitter failure in a hydro, aero or drip system - [Cloudy, foamy or slimy reservoir](https://genetixbay.com/knowledge/diagnose/reservoir-cloudy.md): likely causes Algae from light reaching wet surfaces or the reservoir, Reservoir or root zone too warm, Root rot (Pythium) - [Root-zone or reservoir pH climbing steadily](https://genetixbay.com/knowledge/diagnose/ph-rising.md): likely causes Hard, alkaline water pushing pH up over weeks, High root-zone pH locking out iron, manganese, zinc, boron and copper, Algae from light reaching wet surfaces or the reservoir - [Reservoir pH falling fast without explanation](https://genetixbay.com/knowledge/diagnose/ph-falling.md): likely causes Low root-zone pH starving calcium and magnesium, Ammonium toxicity (too much NH4 in the feed), Root rot (Pythium) - [Reservoir EC rising as the water level drops](https://genetixbay.com/knowledge/diagnose/ec-rising.md): likely causes Nutrient burn (feed too strong) - [Runoff EC well above input EC](https://genetixbay.com/knowledge/diagnose/runoff-ec-high.md): likely causes Nutrient burn (feed too strong), Salt build-up in the root zone, Sodium build-up (softened water, coco, recirculation) - [Runoff EC much lower than input, or reservoir EC dropping fast](https://genetixbay.com/knowledge/diagnose/runoff-ec-low.md): likely causes General underfeeding (whole feed too weak), Nitrogen deficiency - [Medium stays wet for 4+ days after watering](https://genetixbay.com/knowledge/diagnose/medium-stays-wet.md): likely causes Overwatering (roots short of air), Humidity too high / VPD too low, Cold root zone (below about 16 °C / 61 °F) - [Medium dries out within a day; water runs straight through or down the sides](https://genetixbay.com/knowledge/diagnose/medium-dries-fast.md): likely causes Root-bound in a pot too small, Underwatering, Dry, water-repellent medium (water runs straight through) - [White scale on pots, pumps, drippers or the meter](https://genetixbay.com/knowledge/diagnose/white-scale-equipment.md): likely causes Hard, alkaline water pushing pH up over weeks, Cal-Mag overuse (excess calcium and nitrogen) - [Stretched, thin plant with long gaps between nodes](https://genetixbay.com/knowledge/diagnose/stretchy.md): likely causes Normal stretch after the flip, Not enough light - [Excessive stretch after the flip (more than about 3x)](https://genetixbay.com/knowledge/diagnose/excess-flower-stretch.md): likely causes Long-flowering or light-sensitive cultivar, Normal stretch after the flip, Not enough light - [Leggy seedling with a long, thin stem](https://genetixbay.com/knowledge/diagnose/leggy-seedling.md): likely causes Not enough light - [Stunted, slow growth across the plant](https://genetixbay.com/knowledge/diagnose/stunted.md): likely causes Overwatering (roots short of air), Autoflower stunted by early stress, General underfeeding (whole feed too weak) - [One plant much smaller than identical siblings](https://genetixbay.com/knowledge/diagnose/one-plant-stunted.md): likely causes Hop latent viroid (dudding), Weak or slow individual phenotype, Root aphids - [Short internodes, compact growth and small leaves](https://genetixbay.com/knowledge/diagnose/compact-small-leaves.md): likely causes Hop latent viroid (dudding), Light burn: too much light for the plant's climate and CO2, Cold stress - [Seedling stalled for over a week](https://genetixbay.com/knowledge/diagnose/seedling-stalled.md): likely causes Overwatering (roots short of air), Autoflower stunted by early stress, Fungus gnats - [Autoflower started flowering while still small](https://genetixbay.com/knowledge/diagnose/auto-small.md): likely causes Autoflower stunted by early stress, Overwatering (roots short of air), Recovery stall after topping, supercropping or heavy defoliation - [Flowering plant pushing new leafy growth instead of buds](https://genetixbay.com/knowledge/diagnose/reveg-in-flower.md): likely causes Light leak or interrupted dark period, Re-vegetation from too-long days in flower - [Sudden leaf drop over a day or two](https://genetixbay.com/knowledge/diagnose/leaf-drop-sudden.md): likely causes Cold stress - [Fine pale stippling (tiny white or yellow dots) on leaf tops](https://genetixbay.com/knowledge/diagnose/stippling.md): likely causes Twospotted spider mites, Thrips, Whiteflies - [Fine silk webbing on leaves, buds or tips](https://genetixbay.com/knowledge/diagnose/webbing.md): likely causes Twospotted spider mites - [Tiny moving dots under the leaves](https://genetixbay.com/knowledge/diagnose/moving-dots-underside.md): likely causes Twospotted spider mites - [Silvery streaks or patches dotted with black specks](https://genetixbay.com/knowledge/diagnose/silvering.md): likely causes Thrips - [Clusters of soft, pear-shaped insects on stems or leaf undersides](https://genetixbay.com/knowledge/diagnose/aphid-clusters.md): likely causes Aphids - [White flakes (shed insect skins) on leaves](https://genetixbay.com/knowledge/diagnose/white-cast-skins.md): likely causes Aphids - [Tiny white flies that rise when the plant is shaken](https://genetixbay.com/knowledge/diagnose/whiteflies.md): likely causes Whiteflies - [Caterpillars on leaves or buds](https://genetixbay.com/knowledge/diagnose/caterpillars-visible.md): likely causes Caterpillars and budworms - [Ants on the plant](https://genetixbay.com/knowledge/diagnose/ants.md): likely causes Aphids - [Winding pale trails in leaves](https://genetixbay.com/knowledge/diagnose/leaf-trails.md): likely causes Leafminers - [Purple or red veins, mostly on leaf undersides](https://genetixbay.com/knowledge/diagnose/purple-veins.md): likely causes Genetic purple colour (anthocyanin), Cold stress, Phosphorus deficiency - [Pinkish-white mould inside buds](https://genetixbay.com/knowledge/diagnose/pink-bud-rot.md): likely causes Fusarium wilt or crown rot - [Brown, crispy bracts or bud tips on the top colas](https://genetixbay.com/knowledge/diagnose/bud-tips-burnt.md): likely causes Heat stress, Light bleaching at the canopy top - [Tiny black specks on leaf surfaces](https://genetixbay.com/knowledge/diagnose/thrips-frass.md): likely causes Thrips - [Plant stopped drinking; pot or reservoir level barely drops](https://genetixbay.com/knowledge/diagnose/plant-not-drinking.md): likely causes Overwatering (roots short of air), Root rot (Pythium), Cold root zone (below about 16 °C / 61 °F) - [Condensation or wet leaves at lights-off](https://genetixbay.com/knowledge/diagnose/condensation.md): likely causes Humidity too high / VPD too low, Botrytis bud rot (grey mould) - [Some pots dry while others on the same line stay wet](https://genetixbay.com/knowledge/diagnose/uneven-drip-wetting.md): likely causes Pump, timer, air or emitter failure in a hydro, aero or drip system - [Reservoir or root zone cold (below 16 °C / 61 °F)](https://genetixbay.com/knowledge/diagnose/reservoir-cold.md): likely causes Cold root zone (below about 16 °C / 61 °F) - [Seed shell stuck on the seedling's first leaves](https://genetixbay.com/knowledge/diagnose/seed-shell-stuck.md): likely causes Seed coat stuck on the cotyledons (helmet head) - [Yellow tips on lower fan leaves moving down the leaflet](https://genetixbay.com/knowledge/diagnose/yellow-tips-lower.md): likely causes Nitrogen deficiency, Potassium deficiency - [Newest leaves limp while older leaves stay firm](https://genetixbay.com/knowledge/diagnose/new-growth-limp.md): likely causes Heat stress, Copper deficiency, Boron deficiency - [Water pools on the surface and drains slowly](https://genetixbay.com/knowledge/diagnose/water-pools-slow-drain.md): likely causes Overwatering (roots short of air), Root-bound in a pot too small - [Tiny white insects jumping on the medium surface](https://genetixbay.com/knowledge/diagnose/tiny-white-jumpers-soil.md): likely causes Springtails (harmless soil insects) ## Quick answers One canonical grower question per page, answer first, each linked to its full article. Index: https://genetixbay.com/knowledge/answers/ · JSON: https://genetixbay.com/knowledge/api/answers.json - [Can I flower a photoperiod plant 12/12 from seed?](https://genetixbay.com/knowledge/answers/12-12-from-seed.md): Yes, a photoperiod plant can be grown 12/12 from seed, but it won't flower straight away: it first has to mature, forming its first single flowers at around the 7th node, typically after 3–5 weeks. The result is a short plant with one main cola, ready in roughly 3 months. It suits low headroom or many small plants, but per plant it yields less than a vegged plant. - [Can I grow autoflowers and photoperiods in the same tent?](https://genetixbay.com/knowledge/answers/autos-and-photos-in-one-tent.md): You can grow autoflowers and photoperiods in the same tent, but one schedule must lose. On 18/6 to 20/4 the autos thrive and the photos stay in veg; on 12/12 the photos flower and the autos lose about a third of their daily light, and yield with it. The best plan is to veg photos alongside autos, then flip after the autos are harvested, or use two spaces. - [Can I grow cannabis in a closet or cupboard?](https://genetixbay.com/knowledge/answers/can-i-grow-in-a-closet.md): Yes, you can grow cannabis in a closet or cupboard if it can be made light-tight, ventilated and safely powered. A space about 60 x 60 cm (2 x 2 ft) and 140–180 cm tall suits one or two plants under a 100–150 W efficient LED, with an extractor fan changing the air about once a minute through a carbon filter. Check local rules first. - [Can I grow seeds I found in my weed?](https://genetixbay.com/knowledge/answers/can-i-grow-bag-seed.md): You can grow seeds found in your weed, but bag seed is a gamble. Seed in sinsemilla bud often comes from a plant that hermed and pollinated itself, so it tends to be nearly all female and to pass the herm tendency on. Its parents, sex and flowering time are unknown. It is fine for practice; for a real grow, buy documented seed. Check local seed rules first. - [Can you clone an autoflower?](https://genetixbay.com/knowledge/answers/can-you-clone-autoflowers.md): You can root a cutting from an autoflower, but it is impractical. The clone keeps flowering on its parent's age-based clock, so it starts flowering while it is still rooting and finishes tiny, often only a few grams. An autoflower also can't be kept as a mother. To repeat a good auto, grow its seed again, or breed from it. - [How long do autoflowers take from seed to harvest?](https://genetixbay.com/knowledge/answers/how-long-do-autoflowers-take.md): Autoflowers usually take about 9–14 weeks from sprouting to harvest, with fast lines near week 9–10 and long lines near week 13–14. They start flowering at about 3–5 weeks old whatever the light schedule. Add 1–2 weeks of drying before the buds are smokeable. Any setback, such as overwatering, transplanting or hunger, costs time the plant can't recover. - [How many plants can I fit in my grow tent?](https://genetixbay.com/knowledge/answers/how-many-plants-per-tent.md): A grow tent fits about one or two trained plants in 60 x 60 cm (2 x 2 ft), two in 2 x 4 ft and two to four in 4 x 4 ft: roughly 1–4 plants per square metre. A sea of green packs 9–25 small plants per square metre. More plants raise yield per area only up to a point, and legal plant limits usually decide first. - [How much electricity does a home grow use?](https://genetixbay.com/knowledge/answers/electricity-cost-of-growing.md): A home grow uses about 300 kWh per photoperiod run in a 2 x 2 ft tent (150 W LED plus fans) and about 850 kWh in a 4 x 4 ft tent (500 W LED plus fans), with 4 weeks of veg at 18/6 and 10 weeks of flower at 12/12. At 0.15 per kWh that is roughly 45 and 130 in local currency. Dehumidifiers and heaters add more. - [How much weed does one plant produce?](https://genetixbay.com/knowledge/answers/how-much-does-one-plant-yield.md): One indoor cannabis plant produces whatever its share of the canopy yields: roughly 100–500 g of dry flower per square metre of canopy in controlled trials, depending mostly on light. A single plant filling a 60 x 60 cm (2 x 2 ft) tent at moderate light gives about 40–180 g (1.5–6 oz). Per plant is a poor measure: yield follows canopy area and light, not plant count. - [How much yield should I expect per watt or per square foot?](https://genetixbay.com/knowledge/answers/grams-per-watt.md): Expect roughly 100–500 g of dry flower per square metre (about 10–50 g, or 0.3–1.6 oz, per square foot) indoors, rising with light; well-run research rooms at 750–900 µmol/m²/s measured 500–750 g/m². Worked back from those trials, that is roughly 0.7–2 g per watt of efficient LED. A 4 x 4 ft tent therefore gives about 150–700 g, set mainly by canopy light. - [How should I feed autoflowers?](https://genetixbay.com/knowledge/answers/feeding-autoflowers.md): Feed autoflowers lighter than photoperiods but don't starve them: plain water or about EC 0.4–0.6 mS/cm for the first two weeks, 0.8–1.2 in weeks 3–4 and 1.2–1.8 in flower, starting at a quarter to half the label rate. Quality bagged soil often needs water only for 2–3 weeks. Feed through to harvest; don't flush. Hunger in week 3 costs yield an auto can't recover. - [How tall do cannabis plants get indoors?](https://genetixbay.com/knowledge/answers/how-tall-do-plants-get-indoors.md): Indoor cannabis usually finishes about 60–150 cm (2–5 ft) tall, because the grower sets the height: a photoperiod plant grows 50–100% taller after the flip, stretchy cultivars up to 3×, so a plant flipped at 40–60 cm ends near 60–150 cm. Autoflowers usually fit a 140–160 cm tent. Outdoors, unrestricted plants reach about 1–5 m (3–16 ft). - [What are pistils?](https://genetixbay.com/knowledge/answers/what-are-pistils.md): Pistils are the female reproductive organs of cannabis flowers. The white or coloured 'hairs' growers call pistils are strictly the stigmas: each female flower has two, sticking out of its bract to catch pollen. They appear first at the nodes as preflowers, then by the hundred in buds, and darken through orange or brown with age, heat or pollination. Judge harvest by trichomes, not pistil colour. - [What are terpenes in cannabis?](https://genetixbay.com/knowledge/answers/what-are-terpenes.md): Terpenes are the volatile aroma compounds cannabis makes in its glandular trichomes, alongside cannabinoids; myrcene, limonene, caryophyllene, pinene and terpinolene are common. Total terpenes average about 2% of flower weight. In nearly 90,000 US lab results, THC-dominant flower fell into three terpene groups. The 'gas' smell comes mostly from trace sulfur compounds, not terpenes. Terpenes evaporate, so drying and storage matter. - [What is THCA?](https://genetixbay.com/knowledge/answers/what-is-thca.md): THCA (tetrahydrocannabinolic acid) is the acid form of THC that the living cannabis plant actually makes and stores in its trichome heads. Fresh and dried flower is mostly THCA, not THC. Heat (smoking, vaping, baking) removes a CO2 molecule and turns THCA into THC. Labels report total THC = THC + 0.877 × THCA, so 30% THCA means about 26% total THC. - [What is a node on a cannabis plant?](https://genetixbay.com/knowledge/answers/what-is-a-node.md): A node on a cannabis plant is the point on a stem where a leaf and its axillary bud attach; branches, flowers, preflowers and clone roots all start there. The stem between two nodes is the internode. Count nodes upward from the cotyledons, which are not counted. Topping is usually done above the 3rd to 5th node, and preflowers often appear around the 4th to 7th. - [What is the difference between THC and CBD plants?](https://genetixbay.com/knowledge/answers/thc-vs-cbd-plants.md): THC and CBD plants are the same species; the difference is which enzyme turns the shared precursor CBGA into cannabinoid acids. THC-dominant plants carry working THCA synthase, CBD-dominant plants CBDA synthase, and mixed 1:1 plants one of each. The trait is inherited as one near-codominant block, so THC x CBD gives mixed F1s and a 1:2:1 split in the F2. - [What is the difference between a strain and a cultivar?](https://genetixbay.com/knowledge/answers/strain-vs-cultivar.md): A cultivar is a formal botanical term: a cultivated plant group that is distinct, uniform and stable when propagated, by seed or cuttings. A strain is the popular cannabis word, used loosely for anything from one clone to a brand name. A chemovar is a cultivar defined by its chemistry. Genetic studies show many strain names don't reliably mean one genotype. - [What is the difference between fan leaves and sugar leaves?](https://genetixbay.com/knowledge/answers/fan-leaves-vs-sugar-leaves.md): Fan leaves are the big palmate leaves, usually 5–9 serrated leaflets on long stalks, that do most of a cannabis plant's photosynthesis and carry few trichomes. Sugar leaves are the small, resin-coated leaves growing out of the buds, trimmed at harvest and often kept for processing. GenetixBay's house rule is 'tuck, don't pluck': keep fan leaves working and move them aside instead of stripping them. - [What is the difference between hemp and marijuana?](https://genetixbay.com/knowledge/answers/hemp-vs-marijuana.md): Hemp and marijuana are the same species, Cannabis sativa. The difference is chemistry, breeding and law: hemp is cannabis grown for fibre, seed or low-THC flower, defined in many laws as no more than 0.3% THC by dry weight, while marijuana is drug-type cannabis bred for high THC. The two groups are genetically distinct populations, and many fibre hemps are bred monoecious. - [What pot size is best for autoflowers?](https://genetixbay.com/knowledge/answers/best-pot-size-for-autoflowers.md): For autoflowers, an 11–15 L (3–4 gal) pot is the usual final pot, and up to 19 L (5 gal) is forgiving for a first grow. Sow the seed straight into it and don't transplant. Bigger pots give bigger plants within reason, but pot size trades against feeding frequency: small pots can still grow big autos if you water and feed often. - [When do autoflowers start flowering?](https://genetixbay.com/knowledge/answers/when-do-autoflowers-start-flowering.md): Autoflowers usually start flowering about 3–5 weeks after sprouting, with white pistils at the main tip around day 21–35, whatever the light schedule. Preflowers at the nodes often appear a few days earlier, in week 4. Photoperiod plants are different: they flower only after long nights begin, with pistil clusters about 10–14 days after the switch to 12/12. - [When do cannabis plants show their sex?](https://genetixbay.com/knowledge/answers/when-do-plants-show-sex.md): Cannabis plants usually show their sex about 4–6 weeks from seed under long days, when single preflowers form at the nodes; research found the first pair around the 7th node. You need a 30–60x loupe. Males often show first. For an earlier answer, flower a cutting on 12/12 (about 1–2 weeks) or use a DNA sex test from the first true leaves. - [When should I flip my plants to flower?](https://genetixbay.com/knowledge/answers/when-to-flip-to-flower.md): Flip a photoperiod plant to 12/12 (or 13/11) when it is about half the final height your space allows, because most plants grow 50–100% taller, sometimes up to 3×, in the first two to three weeks after the flip. The plant must also be mature, showing preflowers at the nodes. The flip is not day 1 of flower: real flowering starts about 10–14 days later. - [Why do photoperiod plants need long nights to flower?](https://genetixbay.com/knowledge/answers/why-flowering-needs-darkness.md): Photoperiod cannabis is a short-day plant: it measures the uninterrupted night with phytochrome, a light-sensing pigment, and flowers once the night passes a cultivar-specific critical length, around 10–11 hours of darkness in drug-type cultivars tested. 12/12 works for essentially all cultivars; 13/11 also works for many. Light during the night, even very dim, resets the count and can delay flowering in sensitive cultivars. - [Why is my autoflower so small?](https://genetixbay.com/knowledge/answers/why-is-my-autoflower-small.md): An autoflower ends up small when something slows it in the first 3–5 weeks, before it starts flowering by age. The usual causes are overwatering a seedling in a big wet pot, transplant shock, a small pot, topping, weak light under about 300–600 µmol/m²/s, or hunger and pH problems. The auto keeps its countdown regardless, so the lost growth never comes back. - [What should I do with a male plant?](https://genetixbay.com/knowledge/answers/what-to-do-with-a-male-plant.md): A male cannabis plant must leave the flowering room before its pollen sacs open, usually within 1–2 weeks of showing, or it will seed every female. That doesn't mean binning it. Males carry half of every seed's genes, and GenetixBay encourages and rewards them. Either isolate a good male, collect and store its pollen and record it in the Stud Book, or remove it if you're not breeding. - [Can I root clones in plain water?](https://genetixbay.com/knowledge/answers/rooting-clones-in-water.md): Yes. Cannabis cuttings can root in plain water, usually in 10–21 days, but results are less even than in a plug or aeroponic cloner. Keep the water dark, at 20–24 °C (68–75 °F), change it every 2–3 days, and add an air stone if you can. Move them to medium when roots are 2–5 cm (1–2 in) long; long water roots transplant badly. - [Can I take clones from a flowering plant?](https://genetixbay.com/knowledge/answers/can-i-clone-a-flowering-plant.md): Yes. You can clone a flowering cannabis plant (monster cropping), but expect slower rooting, often 2–4 weeks, and a further 2–6 weeks of odd, single-bladed regrowth while the cutting re-vegs under 18–24 hours of light. Success is best from the first 2–3 weeks of flower, using lower branches with little bud. It's a rescue method; cloning before the flip is far easier. - [Do I need rooting hormone for clones?](https://genetixbay.com/knowledge/answers/do-i-need-rooting-hormone.md): You don't strictly need rooting hormone for cannabis clones, but it clearly helps. In a controlled study, an IBA gel gave 2.1 times the rooting success of a willow-extract gel, and in hemp, hormone-treated cuttings rooted far better than untreated ones. Use an IBA gel or powder (commonly 1,000–3,000 ppm), dip once from a decanted portion, and expect roots in 7–14 days. - [Do clones need nutrients before they root?](https://genetixbay.com/knowledge/answers/do-clones-need-nutrients.md): No. Unrooted cannabis clones don't need nutrients: they live on reserves in their stem and leaves, and plain water or a very weak solution (EC up to about 0.4 mS/cm, 200 ppm500) is enough. Strong feed can burn the cut stem. Once roots show, feed rooted clones and seedlings at a quarter to half strength, EC 0.4–0.8 mS/cm (200–400 ppm500). - [How do I clone a cannabis plant?](https://genetixbay.com/knowledge/answers/how-to-clone-cannabis.md): To clone cannabis, cut an 8–15 cm (3–6 in) shoot tip with 2–3 nodes from a healthy vegetative plant, cut below a node with a clean blade, dip it in IBA rooting gel and set it in a moist plug. Keep it at 22–26 °C (72–79 °F), 75–90% RH under gentle light of 50–150 µmol/m²/s. Most cuttings root in 7–14 days. - [How do I reveg a plant after harvest?](https://genetixbay.com/knowledge/answers/how-to-reveg-a-plant.md): To reveg a photoperiod cannabis plant after harvest, leave the lower branches with some leaves and small buds, put it back on 18/6 or 24/0, feed lightly and wait. Expect 2–6 weeks of rounded, single-bladed leaves before normal growth returns. Success varies: stripped, very late or autoflower plants usually fail. Clone the new shoots as soon as they look normal. - [How long do clones take to root?](https://genetixbay.com/knowledge/answers/how-long-do-clones-take-to-root.md): Most cannabis clones root in 7–14 days, with the first roots showing around days 7–12 at a medium temperature of 22–26 °C (72–79 °F), high humidity and gentle light. Cuttings in a cold medium, from flowering plants or without rooting hormone can take 2–4 weeks or fail. If nothing after 3 weeks, check medium temperature, wetness and the cutting's source. - [Is a clone the same sex and age as its mother?](https://genetixbay.com/knowledge/answers/is-a-clone-the-same-as-its-mother.md): A cannabis clone is genetically the same as its mother, including her sex: every clone of a female is female. It is also physiologically mature, not a new seedling, so it can flower as soon as it gets 12/12. Apart from rare somatic mutations and carried-over pathogens such as hop latent viroid, it is the same genotype; there is zero genetic drift. - [What humidity and light do clones need?](https://genetixbay.com/knowledge/answers/humidity-and-light-for-clones.md): Unrooted cannabis clones do best at 75–90% RH (a leaf VPD of about 0.2–0.5 kPa), a medium temperature of 22–26 °C (72–79 °F), and gentle light of 50–150 µmol/m²/s on 18–24 hours, a DLI of about 3–10 mol/m²/day. Once roots show, lower humidity over 3–5 days toward 65–75% and raise light toward 150–300 µmol/m²/s. - [What is the best medium for rooting clones?](https://genetixbay.com/knowledge/answers/best-medium-for-rooting-clones.md): There's no single best medium for rooting cannabis clones; the best is the one that stays moist while holding plenty of air. Studies disagree: rockwool rooted best (up to 80%) in one hemp trial, but worst (0% at 9 days) when kept at full water capacity in another, where a 50:50 peat-perlite mix won. Rockwool, peat or coco plugs and aeroponic cloners all work if not waterlogged. - [When are rooted clones ready to transplant?](https://genetixbay.com/knowledge/answers/when-to-transplant-clones.md): Rooted cannabis clones are ready to transplant when several white roots, about 2–5 cm (1–2 in) long, are poking out of the sides or base of the plug, usually 10–14 days after cutting. Harden them off from the dome over 3–5 days first. Move them into a 0.5–3 L pot of pre-moistened medium at the same pH and keep light gentle for a few days. - [Why are my clones wilting?](https://genetixbay.com/knowledge/answers/why-are-my-clones-wilting.md): Cannabis clones wilt because they have no roots to replace the water their leaves lose. Some droop on day 1–2 is normal; lasting wilt means humidity is too low (aim 75–90% RH), light or heat too strong (keep 50–150 µmol/m²/s), or the stem rotting in a soggy plug. Yellowing after a week is usually the cutting using its stored reserves, not a disaster. - [Are praying leaves a good sign?](https://genetixbay.com/knowledge/answers/praying-leaves.md): Praying leaves, with fan leaves angled upwards and the blades flat, usually mean a cannabis plant is well watered and getting good light. It is a good sign, but not proof of perfect health. If the leaf edges curl up into a taco near the lamp, that is heat or light stress: keep leaf temperature under about 30 °C (86 °F). Leaves often lower again at night, which is normal. - [Can you smoke buds from a hermaphrodite plant?](https://genetixbay.com/knowledge/answers/can-you-smoke-a-hermie.md): Yes, buds from a hermaphrodite plant can be used if they are free of mould. The herm doesn't make them unsafe, but if they were pollinated, seed formation lowers quality and seeds need picking out. Finish or harvest the plant, pick out the seeds, check the buds for rot, and never keep the plant as a mother or grow its seeds. A herm is a genetic defect to cull. - [How do I stop my plants from turning hermaphrodite?](https://genetixbay.com/knowledge/answers/how-to-prevent-hermaphrodites.md): Prevent hermaphrodites by starting with well-bred genetics first, then removing the stresses that reveal weak plants. Choose lines with a published herm rate and plant count, keep the 12-hour dark period fully light-tight, hold canopy temperature under about 30 °C (86 °F), and avoid heavy pruning or drought in flower. A herm is mainly a breeding fault: cull any plant that herms and never breed from it. - [Is it normal for leaves to droop at night?](https://genetixbay.com/knowledge/answers/leaves-droop-at-night.md): Yes, cannabis leaves commonly droop or lower during the dark period and lift again within an hour or two of lights-on. Daily leaf movement is normal in many plants. Worry only if the leaves are still drooping 2 hours after lights-on, or droop during the day: then lift the pot to check for over- or underwatering, and check the roots if the pot is a normal weight. - [Why are my pistils turning brown early?](https://genetixbay.com/knowledge/answers/pistils-turning-brown-early.md): Pistils that brown early, before about week 6 of flower, have usually been pollinated, heat- or light-stressed near the lamp, handled, or are the cultivar's normal colour. They are not a harvest signal by themselves. Check the buds nearest the light (leaf temperature under about 30 °C / 86 °F), look for seeds and anthers, and judge ripeness by calyx trichomes under 60–100× magnification. - [Why are my stems weak and floppy?](https://genetixbay.com/knowledge/answers/weak-floppy-stems.md): Weak, floppy cannabis stems usually come from too little light, which makes plants stretch, and too little air movement, because stems thicken in response to being moved. Give seedlings and veg plants enough light, run a fan so leaves flutter gently at about 0.3–1.0 m/s, and support heavy flowering branches with a trellis or stakes. If the whole plant wilts, check the watering first. - [Why are there seeds in my buds?](https://genetixbay.com/knowledge/answers/why-are-there-seeds-in-my-buds.md): Seeds in cannabis buds mean the flowers were pollinated, usually weeks before harvest. With no male in the room, the usual source is a hermaphrodite: a female growing anthers, often hidden inside the buds. Herm-prone plants are mainly the result of poor breeding, and stress reveals them. Find the source, cull the herm, and don't grow the seeds: they carry the same tendency. - [Why is my plant growing single-finger leaves?](https://genetixbay.com/knowledge/answers/single-finger-leaves-reveg.md): Single-finger, rounded leaves on a cannabis plant usually mean it is revegging: switching from flowering back to vegetative growth because its nights became too short or were broken by light. Common causes are light leaks in flower, timer faults, outdoor plants put out under short spring days, and clones cut from flowering plants. Keep the dark period truly dark, below about 0.01–2 µmol/m²/s. - [Why is my whole plant pale or light green?](https://genetixbay.com/knowledge/answers/whole-plant-pale-green.md): A cannabis plant that is pale all over is usually short of nitrogen, or has roots that can't take nitrogen up because they are overwatered, cold or at the wrong pH. Check the root zone first: pH 6.0–7.0 in soil, 5.5–6.5 in coco and hydro, and roots at about 20 °C (68 °F). Then raise nitrogen modestly, by 10–20%. Some cultivars are naturally lime green. - [Do milk or baking soda sprays work for powdery mildew?](https://genetixbay.com/knowledge/answers/home-remedies-for-powdery-mildew.md): Milk and bicarbonate sprays suppress powdery mildew on leaves; they do not cure it. Trials on squash and pumpkin found milk above about 10% and 0.5% bicarbonate plus oil cut disease, but there are no cannabis trials. Use them only in veg, with full coverage every 7–10 days, alongside airflow and stable humidity. Never spray them on buds after the first 2–3 weeks of flower. - [How do I stop algae in my reservoir or on my medium?](https://genetixbay.com/knowledge/answers/algae-in-reservoir.md): Algae in a cannabis reservoir or on the medium means light is reaching wet, nutrient-rich surfaces. Stop it by keeping light out: opaque reservoirs and lids, no gaps around net pots, covered tubing, and a dry or covered top layer on coco and rockwool. Keep the solution at 18–22 °C (64–72 °F). Scrub and disinfect between runs. Algicides and routine peroxide are not the fix. - [My buds got mouldy in the jar: what now?](https://genetixbay.com/knowledge/answers/mould-in-curing-jars.md): Mouldy buds in a curing jar must be thrown away, not trimmed and smoked. Mouldy flower carries spores and possible mycotoxins. Bin every bud with fuzz, grey dust or brown inner tissue, then open every other jar and check it. Spread the rest out to dry until a sealed sample reads a stable 55–65% RH (water activity 0.55–0.65). Jar mould usually means buds went in too wet. - [Should I wash my buds after harvest?](https://genetixbay.com/knowledge/answers/should-i-wash-my-buds.md): Wash buds only if they are dirty, such as outdoor plants covered in dust, ash, pollen or insects. Washing doesn't rescue buds with powdery mildew or bud rot, and no study shows it removes mould. If you do wash, shake the water off at once and hang the buds in moving air so the extra water doesn't start mould. Indoor plants from a clean room don't need washing. - [What is the white fuzz on top of my soil?](https://genetixbay.com/knowledge/answers/white-fuzz-on-soil.md): White fuzz on top of cannabis soil is usually harmless fungal growth (mycelium) feeding on organic matter in a surface that stays wet. It rarely harms the plant, but it means you water too often or the air is too still, and wet surfaces breed fungus gnats. Let the top 3–5 cm dry between waterings and move air over the pots. A hard, crunchy white crust is salt, not fungus. - [Are purple (blurple) LEDs as good as white LEDs?](https://genetixbay.com/knowledge/answers/blurple-vs-white-led.md): Purple (blurple) LEDs grow cannabis about as well as white LEDs at the same PPFD, because photon quantity and efficacy matter far more than colour. White LEDs win in practice: green light reaches lower leaves, you can see deficiencies and pests, and good white fixtures exceed 2.5–3 µmol/J. Judge any LED by its measured PPFD and µmol/J, not its colour. - [Can I grow cannabis with household LED or CFL bulbs?](https://genetixbay.com/knowledge/answers/can-i-grow-with-household-bulbs.md): You can keep seedlings and clones alive under household LED or CFL bulbs, but you can't grow good flower with them. Seedlings need about 150–300 µmol/m²/s; flower wants 600–1,200 µmol/m²/s over the whole canopy, which takes roughly 25–40 W of efficient horticultural LED per square foot. A handful of household bulbs delivers a fraction of that, so yields are small and buds airy. - [Can I open my tent during the dark period?](https://genetixbay.com/knowledge/answers/opening-tent-during-dark-period.md): You can open a flowering tent during the dark period only if the room outside is dark too, and briefly. Light in the dark period, even very dim, can delay or weaken flowering: delays have been reported from about 2 µmol/m²/s in hemp and 0.01 µmol/m²/s in sensitive cannabis. If you must work, use a dim green headlamp for a few minutes. In veg, it doesn't matter. - [Do I need an intake fan or is passive intake enough?](https://genetixbay.com/knowledge/answers/do-i-need-an-intake-fan.md): Passive intake is enough for most grow tents: an exhaust fan pulls air out and low, open intake ports let fresh air in, keeping the tent under slight negative pressure so smell can't escape. Make the open intake area about 2–3 times the exhaust duct area. Add an intake fan only for big rooms or long intake runs, and keep it weaker than the exhaust. - [How can I measure PPFD without a PAR meter?](https://genetixbay.com/knowledge/answers/measure-ppfd-without-a-par-meter.md): Without a PAR meter, estimate PPFD from the fixture's published PPFD map at your hanging height, cross-check with watts × µmol/J ÷ canopy area, and use a phone or lux meter only for comparisons. Lux-to-PPFD conversion depends on spectrum (about 54 lux per µmol/m²/s in sunlight) and phone apps are often off by 20 % or more. Watch the top leaves to confirm. - [How cold is too cold for cannabis?](https://genetixbay.com/knowledge/answers/how-cold-is-too-cold.md): Cannabis gets too cold when air at the canopy stays below about 15 °C (59 °F): growth, water use and ripening slow sharply, and humid cold nights invite bud rot. Lights-on air below about 20 °C (68 °F) already costs growth. Late-flower nights of 16–20 °C (61–68 °F) are fine. Keep the root zone at 18–22 °C (64–72 °F); cold roots stall a plant even when the air is warm. - [How do I check if my hygrometer is accurate?](https://genetixbay.com/knowledge/answers/calibrate-a-hygrometer.md): Check a hygrometer with a salt test: seal it for 12–24 hours in a bag or jar with a damp slurry of table salt, which holds air at about 75 % RH at room temperature. Note how far it reads off and correct for that. For a second point, magnesium chloride gives about 33 %. Cheap sensors drift 3–5 % RH, enough to mislead VPD and bud-rot decisions. - [How do I keep my grow tent warm in winter?](https://genetixbay.com/knowledge/answers/how-to-keep-a-grow-tent-warm.md): Keep a grow tent warm in winter by keeping the light's own heat in: slow the exhaust on a thermostat, insulate the tent and floor, run the lights during the coldest hours, and only then add a thermostat-controlled heater. Hold 24–28 °C (75–82 °F) by day in veg, 22–26 °C (72–79 °F) in flower, nights 3–6 °C (5–10 °F) cooler, and the root zone at 18–22 °C (64–72 °F). - [How do I lower the humidity in my grow tent?](https://genetixbay.com/knowledge/answers/how-to-lower-humidity-in-a-grow-tent.md): Lower grow-tent humidity by removing the water the plants transpire: more exhaust if the room air is drier, then a dehumidifier sized to roughly the litres you irrigate per day, running through lights-off. Targets are 55–70 % RH in veg, 50–60 % in early flower and 40–50 % in late flower. Ramp temperature down slowly at lights-off and remove standing water. - [How do I lower the temperature in my grow tent?](https://genetixbay.com/knowledge/answers/how-to-cool-a-grow-tent.md): Lower grow-tent temperature by removing the light's heat faster: more exhaust from a cooler room, drivers or ballasts outside the tent, lights dimmed 10–20 %, and lights run in the coolest hours. Aim for 24–28 °C (75–82 °F) in veg and 22–26 °C (72–79 °F) in flower. Above about 30 °C (86 °F) without added CO₂, photosynthesis falls. - [How do I raise the humidity in my grow tent?](https://genetixbay.com/knowledge/answers/how-to-raise-humidity-in-a-grow-tent.md): Raise grow-tent humidity by keeping the water your plants transpire: slow the exhaust first, then add a humidifier on a humidistat. Targets are 65–75 % RH for seedlings, 55–70 % in veg and 50–60 % in early flower. Low RH matters most for seedlings and clones; in late flower, 40–50 % is the goal, so dry air is rarely a problem then. - [How do I stop my grow tent from smelling?](https://genetixbay.com/knowledge/answers/how-to-control-grow-smell.md): Stop a grow tent smelling by keeping it under negative pressure and sending all exhaust air through an activated-carbon filter rated at or above the fan's airflow. Size the fan for about one tent air exchange per minute plus 25–50 % for filter and duct losses, seal unused ports, and keep RH below about 60 %. Never use an ozone generator in an occupied home. - [How long does a carbon filter last?](https://genetixbay.com/knowledge/answers/how-long-does-a-carbon-filter-last.md): A grow-tent carbon filter usually lasts about 12–18 months of continuous use, less in humid rooms or with very pungent cultivars, longer if it only runs in flower. Replace it when you can smell flowering plants at the exhaust outlet. A washable pre-filter sleeve cleaned monthly, and RH kept below about 60 %, are what stretch filter life. - [How long does the flowering stage take?](https://genetixbay.com/knowledge/answers/how-long-does-flowering-take.md): Most photoperiod cannabis flowers for about 7–10 weeks, counted from the first pistil clusters, but harvest comes about 9–12 weeks after the flip, because the flip isn't day 1 of flower: a 10–14 day transition comes first. A breeder's '8 weeks' usually means harvest about 9.5–10 weeks after switching to 12/12. Long-flowering equatorial types can take 11–16 weeks or more. - [In which weeks of flower do buds grow the most?](https://genetixbay.com/knowledge/answers/when-do-buds-grow-the-most.md): Cannabis buds put on most of their mass from roughly week 3 to week 7 of flower, counted from the first pistil clusters, and keep gaining weight and resin right through the final weeks. In one controlled trial, inflorescence dry weight kept increasing at every harvest from week 5 to week 11. That is why the last weeks need full light and feed: taper nitrogen, don't flush. - [LED or HPS: which is better for cannabis?](https://genetixbay.com/knowledge/answers/led-vs-hps.md): LED versus HPS for cannabis quality and yield per photon is an open question at GenetixBay: perhaps. At equal PPFD, research shows similar yields, while LED wins clearly on running cost, about 2.5–3 µmol/J against roughly 1.7 µmol/J for HPS, and on leaf heat load. One small trial found more flower mass under HPS but higher cannabinoid concentration under LED. A Bay Trial will test it. - [Should I mist my plants?](https://genetixbay.com/knowledge/answers/should-i-mist-my-plants.md): Don't mist established cannabis plants, and never mist buds in flower. A spray of water raises humidity for minutes, not hours, and wet leaves and buds invite powdery mildew and bud rot. Misting is useful only for unrooted clones under a dome, at 75–90 % RH. To raise humidity for growing plants, use a humidifier on a humidistat or slow the exhaust. - [Should I run my room warmer with LEDs than with HPS?](https://genetixbay.com/knowledge/answers/led-grow-room-temperature.md): Yes, run an LED room about 1–3 °C (2–5 °F) warmer than an HPS room. Under LEDs, well-watered leaves usually sit 1–3 °C below air temperature; under HPS they sit near or above it, because HPS radiates more heat onto the leaf. For a target leaf temperature of about 24–27 °C (75–81 °F), that means roughly 26–28 °C (79–82 °F) air under LED. Measure leaves with an IR thermometer. - [Should my exhaust fan run 24/7?](https://genetixbay.com/knowledge/answers/run-exhaust-fan-24-7.md): Yes, in most vented tents the exhaust fan should run 24/7, slowed by a temperature and humidity controller rather than switched off. Lights-off is when humidity spikes and, in flower, when smell builds, so an off fan invites bud rot and odour. Circulation fans should always run 24 hours. The exception is a sealed CO₂ room, where exhaust stays off during lights-on. - [What happens if my lights accidentally stay on during flower?](https://genetixbay.com/knowledge/answers/lights-stayed-on-during-flower.md): One accidental 24-hour light period in flower usually costs a photoperiod plant a day or two, not the crop. Fix the timer and return to your normal 12/12 or 13/11 straight away; no long 'make-up' darkness is needed. It matters most in the first two weeks after the flip, when induction can stall. Watch for pollen sacs for 2–3 weeks: a plant that herms from one night is herm-prone. - [What should I look for when buying a grow light?](https://genetixbay.com/knowledge/answers/what-to-look-for-in-a-grow-light.md): When buying a grow light, look first for efficacy above about 2.5 µmol/J, a measured PPFD map over your tent's footprint showing 600–900 µmol/m²/s average with edges at least 70–80 % of the centre, and a real wattage at the wall. Then a dimmer, a broad white spectrum, a driver you can mount outside the tent and an electrical safety certification. Ignore lumens and 'equivalent watts'. - [What wattage LED do I need for my tent?](https://genetixbay.com/knowledge/answers/what-wattage-light-for-my-tent.md): For flower, plan on roughly 25–40 W of efficient LED (2.5–3.0 µmol/J) per square foot, about 270–430 W/m², which gives an average of about 600–900 µmol/m²/s. That's 100–150 W for a 2 × 2 ft tent, 225–320 W for 3 × 3, 200–300 W for 2 × 4 and 400–650 W for 4 × 4. Experienced growers pushing 1,000–1,200 µmol/m²/s need about 35–50 W/ft². - [Why don't lumens matter for grow lights?](https://genetixbay.com/knowledge/answers/lumens-vs-ppfd.md): Lumens don't matter for grow lights because lumens, lux and foot-candles measure light as the human eye sees it, weighted heavily to green-yellow, while plants use photons from 400–700 nm about equally. The plant-relevant numbers are PPF (µmol/s from the fixture), PPFD (µmol/m²/s at the canopy), DLI (mol/m²/day) and efficacy (µmol/J). Lux converts to PPFD only roughly, and only for a known spectrum. - [How do I set up a grow tent?](https://genetixbay.com/knowledge/answers/how-to-set-up-a-grow-tent.md): Set up a grow tent in this order: check the circuit, build the frame, hang the carbon filter high with the exhaust fan pulling through it, open low intakes on the far side, hang the light level over the canopy, add a clip fan, mount power off the floor, then run the empty tent for 48 hours, logging temperature and RH, before any plant goes in. - [Is an indoor grow a fire risk?](https://genetixbay.com/knowledge/answers/grow-room-electrical-safety.md): An indoor grow is a real fire risk only when it's set up badly: overloaded circuits, daisy-chained power strips, damaged cords, heaters and water near plugs. Keep continuous load under 80 % of the circuit (about 1,440 W on a 15 A, 120 V circuit; about 2,900 W on 16 A, 230 V), use RCD/GFCI protection, give cables drip loops and fit a working smoke alarm. - [What meters do I actually need for growing?](https://genetixbay.com/knowledge/answers/meters-you-need-for-growing.md): For a first grow you need three meters: a pH meter calibrated with pH 7 and pH 4 buffers, an EC meter checked against a 1.413 mS/cm standard, and a thermo-hygrometer with min/max memory, salt-tested for accuracy. An IR thermometer is a cheap fourth. A PAR meter is worth it once you grow regularly. A meter you don't calibrate is worse than none. - [What size grow tent should I get?](https://genetixbay.com/knowledge/answers/what-size-grow-tent.md): For a first grow, a 60 × 60 cm (2 × 2 ft) to 90 × 90 cm (3 × 3 ft) tent, 160–180 cm (5.3–6 ft) tall, is the forgiving choice: one to three plants and a 100–320 W LED. A 120 × 120 cm (4 × 4 ft) tent suits two to four plants and 400–650 W. Check your legal plant limit and ceiling first. - [Can I plant seeds straight into the final pot?](https://genetixbay.com/knowledge/answers/plant-straight-into-final-pot.md): Yes. You can plant cannabis seeds straight into the final pot, and for autoflowers it's the GenetixBay house position: sow into an 11–15 L final pot, because any setback costs an auto time. Photoperiods can be sown direct too. The catch is watering: wet only a small circle around the seedling for the first 2–3 weeks, or the big unrooted volume stays soggy. - [Do cannabis seedlings need a humidity dome?](https://genetixbay.com/knowledge/answers/do-seedlings-need-a-dome.md): Cannabis seedlings don't strictly need a humidity dome, but one helps in dry rooms for the first 3–7 days by holding 65–75% RH around them. Vent it daily, and remove it gradually once the first true leaves are growing well. A dome left closed for days breeds mould and damping-off. If your room already sits at 60–70% RH, skip the dome. - [Do cannabis seeds need light to germinate?](https://genetixbay.com/knowledge/answers/do-seeds-need-light-to-germinate.md): No. Cannabis seeds do not need light to germinate; they need warmth (22–27 °C / 72–81 °F), moisture and air, and germinate well in the dark. Light becomes essential the moment the seedling breaks the surface: start at about 100–200 µmol/m²/s for 18 hours, rising to 150–300. A seedling left in the dark after emerging stretches and weakens within a day or two. - [Do seeds that float mean they are duds?](https://genetixbay.com/knowledge/answers/do-floating-seeds-mean-duds.md): No. A cannabis seed that floats is not necessarily a dud; the float test is unreliable because it mostly measures air trapped in or on the shell, and many floaters sink within a few hours and germinate normally. The only reliable check is a germination test: 10 seeds on a damp towel at 22–26 °C (72–79 °F) in the dark for 7 days. - [How long is the seedling stage?](https://genetixbay.com/knowledge/answers/how-long-is-the-seedling-stage.md): The cannabis seedling stage lasts about 2–3 weeks from emergence. It ends when the plant has 3–4 nodes of true leaves with full-sized, multi-fingered leaflets and roots filling a small pot; then it's in veg. At 150–300 µmol/m²/s, 18 hours a day and 23–27 °C (73–81 °F) it moves fastest. Cold, low light or overwatering can stretch it to 4 weeks or more. - [What do I do if the seed shell is stuck on my seedling?](https://genetixbay.com/knowledge/answers/seed-shell-stuck-on-seedling.md): A seed shell stuck on a cannabis seedling (helmet head) usually comes off by itself within a day or two. Mist it, keep the air humid at 65–75% RH, wait 24–48 hours, then ease it off gently only if it is still trapping the leaves. Pulling a dry shell can snap the cotyledons or stem. It is most often caused by planting too shallow or a surface that dried out. - [What light schedule should seedlings get?](https://genetixbay.com/knowledge/answers/light-schedule-for-seedlings.md): Photoperiod and autoflower seedlings both do well on 18/6: 18 hours of light at about 150–300 µmol/m²/s, a DLI of 10–19 mol/m²/day. 24/0 is fine too, because cannabis needs no sleep period in veg; it just costs more power, so drop the intensity to keep the same DLI. Never put photoperiod seedlings on 12/12 unless you want them to flower small. - [Which way up do I plant a germinated seed?](https://genetixbay.com/knowledge/answers/which-way-up-to-plant-a-seed.md): Plant a germinated cannabis seed taproot (radicle) pointing down, 0.5–1.5 cm (¼–½ in) deep, in moist, light mix. Move it once the taproot is about 0.5–2 cm long, before it gets long and brittle. If you get it wrong, don't dig it up: the root turns down by itself. Handling and breaking the taproot does more harm than planting it sideways. - [Why are my seedling's leaves yellow or pale?](https://genetixbay.com/knowledge/answers/seedling-leaves-yellow.md): Yellow or pale cannabis seedling leaves usually mean overwatering, too little light, or hunger in an inert medium. Cotyledons yellowing around days 10–14 is often normal as true leaves take over. Check the pot weight and PPFD (150–300 µmol/m²/s) first; in coco, rockwool or hydro, start a light feed at EC 0.4–0.8 mS/cm (200–400 ppm500). Soil seedlings rarely need feed before 2–3 weeks. - [Why is my seedling drooping?](https://genetixbay.com/knowledge/answers/why-is-my-seedling-drooping.md): A drooping cannabis seedling is most often overwatered: a big pot or soggy plug leaves its tiny roots short of oxygen. Less often it is dry, hot or under a light that is too strong. If the stem is pinched and brown at the soil line, it is damping-off and can't be saved. Water small amounts around the stem only when the pot lightens, at 23–27 °C (73–81 °F). - [Why won't my seeds germinate?](https://genetixbay.com/knowledge/answers/why-wont-my-seeds-germinate.md): Cannabis seeds usually fail to germinate because they are too cold, too wet, too dry or old. Fresh seed shows a taproot in 1–5 days at 22–27 °C (72–81 °F); old seed can take up to 10 days. Below about 18 °C (64 °F) germination slows sharply, and soaking longer than 24 hours or a sopping towel can drown the seed. Old seed may still sprout in 1% hydrogen peroxide. - [Can I dry my buds in my grow tent?](https://genetixbay.com/knowledge/answers/can-i-dry-in-my-grow-tent.md): Yes, a grow tent makes a good drying space once the plants are out and the light is off. Keep it dark, at 15–21 °C (60–70 °F) and 55–62% RH, with the exhaust on low and a fan moving room air, not blowing on the buds. Never dry in a tent with the grow light or heat running, or alongside live plants. Expect 7–14 days. - [Can I quick-dry buds in an oven, microwave or paper bag?](https://genetixbay.com/knowledge/answers/quick-drying-methods.md): Quick-drying cannabis in an oven or microwave makes harsh, grassy flower and drives off the volatile terpenes a slow dry keeps; the idea that it is a harmless shortcut is a Myth. Paper bags are a slow method, not a fast one, and work for small amounts in a dry room if turned daily. For good flower, dry in the dark for 7–14 days at 15–21 °C and 55–62% RH. - [How do I check trichomes?](https://genetixbay.com/knowledge/answers/how-to-check-trichomes.md): Check cannabis trichomes with a 60–100× loupe or clip-on phone microscope, looking at the heads on the calyxes, not the sugar leaves. Sample a top cola, a mid-canopy bud and a lower bud, and score the share of clear, cloudy and amber heads. Start checking at the early end of the cultivar's window, counted from the flip plus the 10–14 day transition, and repeat every 2–3 days. - [How do I rehydrate over-dried buds?](https://genetixbay.com/knowledge/answers/rehydrate-over-dried-buds.md): To rehydrate over-dried buds, seal them in a jar with a fresh, slightly moister bud for about a day, then check that the equilibrated jar reads 55–62% RH (water activity 0.55–0.62). This restores the feel, not the lost aroma: a cure never fixes a bad dry. GenetixBay doesn't recommend humidity packs, which rob terpenes, or fruit peel and lettuce, which add mould risk and off-flavours. - [How do I trim buds?](https://genetixbay.com/knowledge/answers/how-to-trim-buds.md): Trim cannabis by removing the big fan leaves at harvest, then snipping or brushing the sugar leaves back to the bud, either wet on harvest day or dry once small stems snap after 7–14 days. Wet versus dry trim is grower preference. Use sharp, small scissors, gloves and a tray to catch trichomes, and keep the trim for hash or edibles. Handle buds by the stem. - [How full should I fill my curing jars?](https://genetixbay.com/knowledge/answers/how-full-to-fill-curing-jars.md): Fill curing jars about three-quarters full, loosely, so the buds don't crush and air can move around them when you burp. A packed jar holds wet pockets and flattens buds. A jar that is mostly empty holds a lot of air and swings humidity. Once the cure is done, after 2–8 weeks, fill storage jars fuller to cut the air in contact with the buds. - [How soon after harvest can I smoke my buds?](https://genetixbay.com/knowledge/answers/how-soon-after-harvest-can-i-smoke.md): Cannabis can be smoked once it is properly dried, usually 7–14 days after harvest, when small stems snap and a sealed sample jar reads a stable 58–65% RH. It is noticeably better after at least 2 weeks of curing, and most growers cure for 4–8 weeks. Fresh or fast-dried samples smoke harsh and grassy and don't represent how the finished crop will taste. - [Should I hang the whole plant or cut branches to dry?](https://genetixbay.com/knowledge/answers/hang-whole-plant-or-branches.md): Hang the whole plant if your dry room runs on the dry side or you want the slowest dry, because the stem and leaves slow water loss. Cut branches if space is tight or the room is humid, since smaller pieces dry faster and evenly. Wet-trimmed buds go on a rack and dry fastest. Whatever the method, aim for 7–14 days at 15–21 °C (60–70 °F) and 55–62% RH. - [Should I harvest the whole plant at once or in stages?](https://genetixbay.com/knowledge/answers/harvest-in-stages.md): Harvest a cannabis plant in stages when the top colas are ready and the lower buds clearly aren't, often a difference of several days. Cut the tops at mostly cloudy with some amber, then give the lower buds roughly 5–10 more days, feeding normally. If the whole plant reads within a few percent, or bud rot or pollen threatens, harvest everything at once. Never flush or darken before either cut. - [What happens if I harvest too early or too late?](https://genetixbay.com/knowledge/answers/harvesting-too-early-or-late.md): Harvest too early and you lose weight and resin: buds are still filling, and cannabinoid concentration hasn't reached its plateau. Harvest too late and the plant senesces, cannabinoid concentration starts falling, and bud-rot risk climbs. The window between is fairly wide. Most growers cut at mostly cloudy with about 5–20% amber, a matter of preference. Amber doesn't mean CBN or couch-lock. - [Why did my buds lose their smell?](https://genetixbay.com/knowledge/answers/buds-lost-their-smell.md): Buds lose their smell mostly because volatile terpenes escaped during a fast, warm or over-dry dry, and then during storage in warmth, light or air. Humidity packs and frequent jar opening make it worse. The aroma doesn't come back: a cure never fixes a bad dry. Next time, dry for 7–14 days at 15–21 °C and 55–62% RH and keep buds at water activity 0.55–0.65. - [Why do my curing jars smell like ammonia?](https://genetixbay.com/knowledge/answers/ammonia-smell-in-jars.md): An ammonia or musty smell in a curing jar means the buds went in too wet and microbes are starting to break them down, a step before visible mould. Act at once: tip the buds out, check the cores for rot, and spread them on a screen to dry until a sealed sample reads a stable 58–65% RH. Burping more often alone won't fix it. - [Why is my homegrown weed harsh?](https://genetixbay.com/knowledge/answers/why-is-my-weed-harsh.md): Homegrown cannabis is usually harsh because it was dried too fast, over-dried, or smoked before a proper cure, not because it wasn't flushed. Flushing is a Myth that costs yield and resin. Dry slowly for 7–14 days at 15–21 °C (60–70 °F) and 55–62% RH, then cure for at least 2 weeks, with water activity falling slowly from about 0.62–0.65 towards 0.55–0.58. - [Can I use regular garden fertiliser on cannabis?](https://genetixbay.com/knowledge/answers/use-regular-plant-fertiliser.md): Yes, regular garden fertiliser works on cannabis in soil, because roots take up the same ions whatever the label says. Pick a complete feed with calcium, magnesium and micronutrients, and dose by element: aim for roughly 150-200 mg/L nitrogen in veg and 30-60 mg/L phosphorus. All-purpose feeds suit veg, tomato feeds suit flower. Avoid lawn feeds with herbicides, and use fully soluble salts in hydro. - [Do banana peels, coffee grounds or eggshells feed cannabis?](https://genetixbay.com/knowledge/answers/kitchen-scraps-as-fertiliser.md): No, not in any useful way: feeding cannabis with kitchen scraps is a Myth. Banana peels hold some potassium but release it only as they rot; peel water is a trace dose. Raw coffee grounds reduced plant growth in a controlled study. Eggshells are calcium carbonate that dissolves very slowly and acts more like lime than feed. Compost the scraps first, and feed the plant properly. - [Do mycorrhizae help cannabis?](https://genetixbay.com/knowledge/answers/do-mycorrhizae-help.md): Mycorrhizae can help cannabis a little, mainly with phosphorus uptake in low-phosphorus soil, but commercial inoculants often don't deliver. In a seedling trial the highest dose raised root length 34% and phosphorus content 24%. A global test of 28 commercial products found most failed to colonise roots. In fully fed hydro or coco, phosphorus is plentiful and colonisation is suppressed, so inoculants are mostly wasted money. - [Does compost tea work for cannabis?](https://genetixbay.com/knowledge/answers/does-compost-tea-work.md): Compost tea is not a meaningful fertiliser for cannabis, and its disease-control effects are inconsistent. Reviews found some teas suppressed some diseases in some trials, with no reliable recipe, and there are no controlled cannabis trials. Adding molasses, kelp or fish to brew grew E. coli and Salmonella 10- to 10,000-fold in one study. If you use it, apply it to living soil, not flowers, within hours of brewing. - [Does foliar feeding work on cannabis?](https://genetixbay.com/knowledge/answers/does-foliar-feeding-work.md): Foliar feeding works on cannabis as a quick, small top-up, not as a feed. Leaves absorb little and unevenly, so a spray can green new growth within days for magnesium, iron or zinc in veg, but it cannot supply nitrogen, potassium or calcium in useful amounts. Use it in veg only, at low light or lights-off, and never spray flowers. Fix the root zone at the same time. - [How do I fix nutrient lockout?](https://genetixbay.com/knowledge/answers/how-to-fix-nutrient-lockout.md): Fix nutrient lockout by finding its cause first: most lockout is root-zone pH out of range, salt build-up or damaged roots, not true antagonism. Calibrate your meter, check runoff pH and EC, and look at the roots. If runoff EC is about 0.8-1.0 mS/cm or more above input, flush the root zone with 2-3 times the pot volume, then resume normal feeding. Correct pH gradually and stop stacking boosters. - [How long can mixed nutrient solution be stored?](https://genetixbay.com/knowledge/answers/how-long-can-mixed-nutrients-sit.md): Mixed mineral nutrient solution keeps about a week if it is covered, dark and cool, roughly the same 7-14 days a DWC reservoir runs between changes; an open, warm, lit jug is best used within 1-3 days. Light breaks down chelated iron, warmth grows microbes, and organic or sugary additives spoil within a day or two. Recheck pH and EC before use. - [In what order should I mix nutrients?](https://genetixbay.com/knowledge/answers/order-to-mix-nutrients.md): Mix nutrients into the full volume of water in this order: silica first, then Cal-Mag or part A, then part B, then any additives, stirring between each, and adjust pH last. Silica first because it is strongly alkaline (pH about 11-12). Calcium and the sulfates and phosphates in part B must meet only once diluted, or they precipitate. Then check EC against your target. - [Is it worth fixing a deficiency in late flower?](https://genetixbay.com/knowledge/answers/fix-deficiency-in-late-flower.md): It depends what you're seeing. Lower fan leaves yellowing in the last 2-3 weeks is normal remobilisation, not a deficiency, so leave it. A real problem that spreads to sugar leaves and new growth with 3 or more weeks to go is worth fixing, usually by correcting root-zone pH or runoff EC and keeping the feed at stage strength. Never flush, and never foliar spray buds. - [Should I feed every time I water?](https://genetixbay.com/knowledge/answers/feed-every-watering.md): Whether to feed every watering depends on the medium. In coco, rockwool and hydro, yes: every irrigation carries nutrient solution at stage strength, about EC 1.2-1.8 mS/cm in veg and 1.6-2.2 in flower. In bagged soil, feed every second or third watering at EC 0.8-1.6 once the starter charge runs out. In living soil, water only and top-dress. Runoff EC tells you if the rhythm is right. - [Should I use full-strength nutrients from the feeding chart?](https://genetixbay.com/knowledge/answers/full-strength-feeding-chart.md): Usually not at first. Feeding charts are written as upper limits, often for hard water and vigorous plants. Start at about half to three-quarters of the chart and steer by EC instead: about 0.6-1.0 mS/cm for seedlings, 1.2-1.8 in veg and 1.6-2.2 in flower for coco and hydro, and 0.8-1.6 in soil. Raise strength only if runoff EC and leaves say the plant wants more. - [What are macronutrients and micronutrients?](https://genetixbay.com/knowledge/answers/macro-vs-micronutrients.md): Macronutrients are the elements cannabis needs in large amounts: nitrogen, phosphorus and potassium (primary) plus calcium, magnesium and sulfur (secondary), fed at roughly 30-250 mg/L each. Micronutrients are needed in traces, under about 3 mg/L: iron, manganese, zinc, copper, boron, molybdenum, plus chloride and nickel. Carbon, hydrogen and oxygen come from air and water. Silicon is beneficial, not essential. - [What does N-P-K mean on a fertiliser label?](https://genetixbay.com/knowledge/answers/what-does-npk-mean.md): N-P-K on a fertiliser label is the guaranteed percentage by weight of nitrogen (N), phosphate (P2O5) and potash (K2O). Only the N figure is the actual element. Multiply the middle number by 0.44 for elemental phosphorus and the last by 0.83 for potassium, so a 10-10-10 holds 10% N, about 4.4% P and 8.3% K. Cannabis feed targets and research use elements in mg/L, not oxides. - [When does pre-fertilised soil run out of nutrients?](https://genetixbay.com/knowledge/answers/when-does-soil-run-out-of-nutrients.md): A typical pre-fertilised bagged potting mix feeds cannabis for about 2-4 weeks, then runs short, usually in mid-veg. Heavily amended or super-soil-style mixes and big pots last longer. The sign is the oldest, lowest leaves turning pale yellow from the tip inward and climbing, which is nitrogen running out. Then start feeding at half the label rate, around EC 0.8-1.6 mS/cm, every second or third watering. - [When should I stop feeding before harvest?](https://genetixbay.com/knowledge/answers/when-to-stop-feeding-before-harvest.md): Don't stop feeding before harvest. Stopping nutrients or flushing with plain water in the last 1-3 weeks is a harmful Myth: the plant is still packing on weight and resin. Feed through to the chop at stage strength. The GenetixBay approach is to taper only nitrogen over the last 3-4 weeks, down to 0-20 mg/L in the final days, while keeping P, K, Ca, Mg, S and micros fed. - [Which nutrients do I actually need for a first grow?](https://genetixbay.com/knowledge/answers/which-nutrients-to-buy.md): For a first grow you need one complete base nutrient made for your medium (soil, or a two-part A and B for coco and hydro), Cal-Mag only if you use RO or soft water or coco, a pH down, and a pH and EC meter. Boosters, sugars and most additives are optional: cannabis trials found no yield gain above about 30-60 mg/L phosphorus or from doubling feed strength. - [Will damaged leaves recover after I fix the problem?](https://genetixbay.com/knowledge/answers/do-damaged-leaves-recover.md): Mostly no. Brown, burnt or dead leaf tissue never recovers, and badly yellowed leaves rarely regreen; only mildly pale leaves may partly recover once the nutrient is back. Judge your fix on new growth, which should look healthy within about 5-10 days. Leave damaged leaves that are still mostly green, because they still photosynthesise. Remove only leaves that are mostly dead, diseased, or shading nothing useful. - [Can I grow autoflowers outdoors?](https://genetixbay.com/knowledge/answers/autoflowers-outdoors.md): Yes: autoflowers grow well outdoors because they flower by age, not day length, finishing about 9–14 weeks from seed. Sow straight into the final container or bed once nights stay above about 10 °C (50 °F). At mid-latitudes a late-spring sowing finishes in mid to late summer, and a second sowing by early summer can finish before autumn rain. Any setback costs yield: no transplanting, LST instead of topping. - [Can I start plants indoors and move them outside?](https://genetixbay.com/knowledge/answers/start-indoors-move-outside.md): Yes: starting photoperiod cannabis indoors 3–6 weeks before your last frost and moving it outside is standard practice, if you harden it off over 7–14 days. Keep it on long days indoors (18 h or more), and move it out only once natural days are about 14.5 hours or longer, or it may flower and re-veg. Autoflowers should start in the final container, which you carry outside. - [How do I grow outdoors in a short northern season?](https://genetixbay.com/knowledge/answers/outdoor-short-season.md): To grow outdoors in a short northern season (roughly 50° latitude and above, with frost by late September or October), pick plants that finish by late September: autoflowers, or early-finishing photoperiod lines. Start indoors 3–6 weeks before last frost, harden off, plant out in early June, and use a greenhouse, hoop cover or light deprivation to dodge autumn rain. Check local rules first. - [How much sun does outdoor cannabis need?](https://genetixbay.com/knowledge/answers/how-much-sun-outdoors.md): Outdoor cannabis needs at least 6–8 hours of direct sun a day, and more is better: full summer sun reaches 1,500–2,000 µmol/m²/s at midday and a daily light integral of roughly 40–60 mol/m²/day on clear days. Yield rises roughly in proportion to light, so a part-shaded spot yields less, not nothing. Under about 4 hours of direct sun, expect thin, airy buds. - [How should I prepare soil or pots for outdoor plants?](https://genetixbay.com/knowledge/answers/outdoor-soil-and-pot-size.md): For outdoor cannabis in the ground, dig a hole about 60–90 cm (2–3 ft) wide and 45–60 cm (18–24 in) deep, mix in compost and perlite or pumice, and aim for soil pH 6.0–7.0 with good drainage. In containers, use potting mix, not garden soil: about 75–380 L (20–100 US gal) for full-season photoperiods and 11–25 L (3–7 US gal) for autoflowers. Bigger holds more water. - [When do outdoor plants start flowering?](https://genetixbay.com/knowledge/answers/when-do-outdoor-plants-flower.md): Outdoor photoperiod cannabis starts flowering when days shorten past its cultivar's threshold, often around 14–14.5 hours of daylight. At 35–50° latitude that is usually late July to mid-August in the Northern Hemisphere and late January to mid-February in the Southern. Plants show pistils over the next 10–14 days. Higher latitudes cross the threshold later; near the tropics plants can flower almost any time. - [When is outdoor cannabis ready to harvest?](https://genetixbay.com/knowledge/answers/when-to-harvest-outdoors.md): Outdoor cannabis is ready when its trichomes are mostly cloudy with some amber (roughly 5–20%), which at 35–50° latitude usually falls between mid-September and late October in the Northern Hemisphere and between March and April in the Southern. Early cultivars finish first; late tropical lines run into November or May. Weather can overrule the trichomes: harvest ahead of long rain spells or a hard freeze. - [When should I plant cannabis outdoors?](https://genetixbay.com/knowledge/answers/when-to-plant-outdoors.md): Plant cannabis outdoors after your last frost, once nights stay above about 10 °C (50 °F). At mid-latitudes (35–50°) that is usually mid-May to mid-June in the Northern Hemisphere and mid-November to mid-December in the Southern. Planting photoperiods much earlier, while days are under about 14 hours, risks early flowering and re-veg. Autoflowers can go out any time with 9–14 warm weeks left. - [Can I use neem oil in flower?](https://genetixbay.com/knowledge/answers/neem-oil-in-flower.md): No: neem oil does not belong on cannabis in flower. 'Natural, so it's safe on buds' is a myth. Neem leaves an oily, bitter residue on resin, wet buds invite bud rot, and azadirachtin (crude neem's active) is one of 96 actives Canada tests licensed cannabis for. Use neem only in veg, and stop all oil sprays before flowers form, roughly by the end of the 10–14 day transition. - [Do sticky traps work?](https://genetixbay.com/knowledge/answers/do-sticky-traps-work.md): Sticky traps work as a monitoring tool, not a cure. Yellow cards catch fungus gnats, whiteflies, winged aphids and leafminers; blue cards are somewhat more attractive to thrips. They catch only flying adults, so they never fix larvae in the medium or spider mites. Count catches weekly and replace the card: a rising count is your early warning, and a falling count shows the real treatment is working. - [How did pests get into my sealed tent?](https://genetixbay.com/knowledge/answers/how-did-pests-get-in-my-tent.md): Pests don't appear from nowhere in a sealed cannabis tent; something carried them in. The usual routes, most likely first, are new clones, your own clothes and hands after the garden, pets and houseplants, unfinished compost or open media bags (fungus gnats), and the intake air for tiny fliers like thrips and whiteflies. Low populations hide for weeks, so the source often predates the symptoms. - [How do I prevent pests in an indoor grow?](https://genetixbay.com/knowledge/answers/how-to-prevent-pests-indoors.md): To prevent pests in an indoor grow, stop them coming in and catch the rest early. Quarantine every new clone for 2–3 weeks, start from seed where you can, keep outdoor clothes, pets and houseplants out, and work clean rooms first. Scout leaf undersides weekly with a 10–20x lens, count sticky cards weekly, release preventive predators in veg, and clean the room between cycles. - [What are the small white bugs in my soil?](https://genetixbay.com/knowledge/answers/small-white-bugs-in-soil.md): Small white bugs in cannabis soil that jump when disturbed are almost always springtails: about 1.5 mm (1/16 in), harmless scavengers of wet, organic media. Slow, round specks are soil mites, often harmless or predatory. The ones that matter are worm-like larvae with a shiny black head (fungus gnats) and pale aphids clustered on roots (root aphids). Tip the plant out and look at the roots. - [What can I safely spray on plants in flower?](https://genetixbay.com/knowledge/answers/what-can-i-spray-in-flower.md): On cannabis in flower, the safe default is to spray nothing on buds. Stop oils, soaps, sulfur and bicarbonates by the first 2–3 weeks of flower; after that, wet buds invite botrytis and residues stay in the product. Outdoors, Bt for small caterpillars is one of the few options, only where registered for cannabis. Otherwise rely on beneficials, removal and climate, and harvest early if needed. - [What is eating holes in my leaves?](https://genetixbay.com/knowledge/answers/holes-in-leaves.md): Holes in cannabis leaves are usually chewing pests, and the clue left behind names them. Dark frass pellets mean caterpillars; silvery slime trails mean slugs or snails; ragged margins on outdoor edge plants mean grasshoppers; a seedling cut through at the soil line means cutworms. Indoors, chewers are rare: holes there are more often dead, dried tissue from nutrient or burn spots falling out. Check at night with a torch. - [Are pH test drops accurate enough?](https://genetixbay.com/knowledge/answers/ph-drops-vs-ph-meter.md): pH test drops and strips are accurate enough for soil and rough water checks, but not for hydro or coco. Colour kits read in steps of roughly 0.5 pH unit and are hard to judge in coloured nutrient solution, while hydro's working band, 5.5-6.2, is only 0.7 wide. A calibrated digital meter reads to 0.1 or better. Use drops as a backup that catches a failing meter. - [Can I use distilled water or rainwater for cannabis?](https://genetixbay.com/knowledge/answers/can-i-use-distilled-water.md): Yes. Distilled, RO and clean rainwater work well for cannabis because they start near EC 0 with no sodium, chloride or alkalinity, but they also carry no calcium or magnesium and no pH buffer. Add a complete feed that includes Ca and Mg, or a Cal-Mag supplement, to reach about 150-200 mg/L Ca and 40-70 mg/L Mg, and expect pH to swing easily. Rain is naturally about pH 5.6. - [Can I use vinegar or lemon juice to lower pH?](https://genetixbay.com/knowledge/answers/vinegar-or-lemon-to-lower-ph.md): You can, but you shouldn't: the idea that vinegar or lemon juice is a fine pH down is a Myth. In a hydroponic trial, vinegar cut yields of lettuce, basil and Swiss chard, and lime juice cut basil and chard yields, while a mineral pH down held pH most steadily with the least product. Kitchen acids are weak and rebound. Use phosphoric, nitric or sulfuric acid. - [Do I really need to pH my water?](https://genetixbay.com/knowledge/answers/do-i-need-to-ph-my-water.md): In coco, rockwool and hydro, yes: adjust every batch to about pH 5.5-6.2 in hydro or 5.8-6.3 in coco, because these media barely buffer pH. In bagged soil, adjusting to pH 6.2-6.8 is good practice but the mix buffers small errors, and your water's alkalinity matters more than its pH. In living soil, generally no. The accepted ranges are soil 6.0-7.0 and soilless 5.5-6.5. - [How do I fix soil pH that is too high or too low?](https://genetixbay.com/knowledge/answers/fix-soil-ph.md): Raise soil pH with agricultural or dolomitic lime and lower it with elemental sulfur; both take weeks, so build them into the mix before planting. In a pot mid-grow, correct slowly through the water instead: pH-adjust each watering and treat hard water's alkalinity. Aim for a root zone of pH 6.0-7.0, ideally 6.2-6.8, and act if runoff stays below about 5.8 or above 7.3. - [How do I raise or lower the pH of my water?](https://genetixbay.com/knowledge/answers/how-to-adjust-ph.md): Lower pH with a mineral acid pH down (phosphoric, nitric or sulfuric) and raise it with potassium hydroxide or potassium silicate, after the nutrients are in. Add a few drops per 10 litres, stir, wait, re-read. In hydro, recheck after 15-30 minutes of circulation. A steady rise of 0.1-0.4 pH per day in a healthy reservoir is normal, from nitrate uptake and aeration stripping CO2. - [Is a TDS meter the same as an EC meter?](https://genetixbay.com/knowledge/answers/tds-meter-vs-ec-meter.md): Yes, essentially. A TDS or ppm meter measures electrical conductivity (EC) and multiplies it by an assumed factor: 0.5 on the 500 scale, 0.7 on the 700 scale, sometimes 0.64. So 1.0 mS/cm reads 500 ppm on one meter and 700 on another. The ppm figure is an estimate, not your nutrients' real concentration. Read and talk in EC, or always state the scale. - [Should I pH my water before or after adding nutrients?](https://genetixbay.com/knowledge/answers/ph-before-or-after-nutrients.md): Adjust pH after adding nutrients. Fertiliser salts, and silica most of all, change the solution's pH, so adjusting plain water first means adjusting twice. Mix everything, stir, then bring the feed to about pH 5.5-6.2 for hydro, 5.8-6.3 for coco or 6.2-6.8 for soil. In hydro, aerate a fresh mix 30-60 minutes before the final reading. Calibrate the meter first. - [Are fabric pots better than plastic pots?](https://genetixbay.com/knowledge/answers/fabric-pots-vs-plastic-pots.md): Fabric pots are better than plastic pots for hand-watered soil, mainly because they dry faster and run cooler. Water evaporates through the walls, which cuts overwatering risk and kept substrate about 6 °C (11 °F) cooler than black plastic in one nursery study. The cost is more frequent watering. Plastic suits automated drip, coco and growers who water rarely. - [Can I mix soil and coco?](https://genetixbay.com/knowledge/answers/can-i-mix-soil-and-coco.md): Yes, you can mix soil and coco: adding buffered coco to potting mix lightens it, holds water well and stays airy. Decide which system the blend behaves like. Mostly soil (coco 50% or less): water at pH 6.2–6.8 and feed at soil strength. Mostly coco: run pH 5.8–6.2 and feed every watering. Use washed, buffered coco or it will grab calcium and magnesium. - [Can I reuse soil from my last grow?](https://genetixbay.com/knowledge/answers/can-i-reuse-soil.md): Yes, you can reuse soil from your last grow if the plants were healthy. Break up the root ball, add fresh compost or worm castings, slow-release organic amendments and perlite, then keep it moist for 2–4 weeks before planting. Don't reuse soil from plants with root rot, wilt or root pests. Coco can be rinsed and re-buffered; living soil is reused in place, no-till. - [How much water does a cannabis plant use per day?](https://genetixbay.com/knowledge/answers/how-much-water-per-day.md): A cannabis plant uses roughly 50–250 mL of water a day as a seedling, 0.5–1.5 L in veg and about 1.5–2 L a day as a large flowering plant indoors. Plan the room at up to about 10 L per m² of flowering canopy per day (1 L per ft²) under strong light and heat. Nearly all of it is transpired, so light, temperature and VPD drive use. - [How often should I water my cannabis plants?](https://genetixbay.com/knowledge/answers/how-often-to-water.md): Water by weight, not by calendar. In soil, water when the pot feels about 40–50% lighter than just after watering, usually every 2–4 days for established plants. Coco and rockwool want watering once to several times a day with 10–30% runoff. Seedlings in big pots need small amounts around the stem. The pot's weight and the plant's size set the schedule, not the day of the week. - [Should I put gravel or rocks in the bottom of my pots?](https://genetixbay.com/knowledge/answers/gravel-in-bottom-of-pots.md): No, you don't need gravel or rocks in the bottom of a pot, and the idea that a drainage layer is necessary to stop waterlogging is a myth. Its effect on drainage is small and disputed, and it takes away root volume. A free-draining mix with 20–35% perlite or pumice, open drainage holes and an empty saucer do the job better. - [Should I top off my reservoir with plain water or nutrient solution?](https://genetixbay.com/knowledge/answers/top-off-reservoir-water-or-nutrients.md): Let the reservoir's EC decide what you top off a hydro reservoir with. If EC has risen since the last check, top off with plain, pH-adjusted water; if it holds steady, top off with solution at the reservoir's current EC; if it falls, the plants are hungry, so use solution at full target strength. Without a meter, plain or quarter-strength water is the safe default. Refresh fully every 7–14 days. - [Should I water when the lights come on or before they go off?](https://genetixbay.com/knowledge/answers/water-at-lights-on-or-off.md): Water cannabis soon after the lights come on, ideally within the first 1–3 hours. Plants transpire mostly in the light, so a morning watering is used during the day and the pot dries back overnight. Watering just before lights-off leaves a wet, cool pot in the dark, which slows dryback, raises humidity and favours fungus gnats and root rot. Drip-fed coco stops irrigating 2–6 hours before lights-off. - [What coco to perlite ratio should I use?](https://genetixbay.com/knowledge/answers/coco-perlite-ratio.md): The usual coco to perlite ratio is 70:30 for hand-watered pots. Coco takes 0–30% perlite: hand watering once a day or less suits 20–30% perlite for extra air and margin, while automated high-frequency drip can run 0–20% or plain coco. More perlite means more air, faster drying and more irrigations; less perlite holds more water. - [What is super soil?](https://genetixbay.com/knowledge/answers/what-is-super-soil.md): Super soil is a heavily amended organic soil, rich in compost, worm castings and slow-release amendments, cooked moist for weeks and meant to feed a cannabis plant through most of its life with plain water. It is usually layered: a strong layer low in the pot, milder soil on top for young roots. Many growers still top-dress in mid flower. - [What soil should I use for growing cannabis?](https://genetixbay.com/knowledge/answers/best-soil-for-cannabis.md): The best soil for growing cannabis indoors is a quality bagged potting mix, peat- or coco-based with compost and a light starter fertiliser, opened up with 20–35% perlite or pumice. Never use garden soil in pots. The starter charge feeds for 2–4 weeks; after that, feed at EC 0.8–1.6 mS/cm with water at pH 6.2–6.8. - [Why does water run straight through or pool on top of my pot?](https://genetixbay.com/knowledge/answers/water-runs-through-or-pools.md): Water runs straight through a pot when the mix has dried out, shrunk from the wall and turned water-repellent, so water channels down the sides and out the bottom while the root ball stays dry. Water pools on top when the surface is crusted or compacted, the mix is too fine, or drainage holes are blocked. Fix both by watering slowly in 2–3 passes or bottom-soaking for 20–30 minutes. - [Can I defoliate autoflowers?](https://genetixbay.com/knowledge/answers/can-i-defoliate-autoflowers.md): You can defoliate autoflowers, but only lightly, and GenetixBay advises tucking instead. An autoflower runs on a fixed countdown of about 9–14 weeks from germination, so any setback costs yield it can't recover. Tuck fan leaves away from bud sites, remove only damaged, dying or soil-touching leaves, take no more than a few at a time, and never schwazz an auto. - [How can I increase my yield indoors?](https://genetixbay.com/knowledge/answers/how-to-increase-yield-indoors.md): Increase indoor yield with more usable light first: dry flower yield rose linearly from 116 to 519 g/m² as canopy PPFD went from 120 to 1,800 µmol/m²/s. Then fill the space with an even canopy, through training or more plants per m², give roots enough volume and water, and feed through to harvest. Defoliation doesn't raise yield; pre-harvest flushing costs it. - [How do I get bigger, denser buds?](https://genetixbay.com/knowledge/answers/how-to-get-bigger-denser-buds.md): Bigger, denser buds come mainly from more light at every bud site: 800–1,200 µmol/m²/s at canopy in flower at ambient CO₂, on an even canopy. Then keep flower days at 22–26 °C (72–79 °F), feed a complete, balanced flower diet through to harvest, and harvest ripe. Bloom boosters, pre-harvest flushing and 48-hour darkness don't help. - [How long does a plant take to recover after topping?](https://genetixbay.com/knowledge/answers/recovery-after-topping.md): A healthy cannabis plant takes about 3–7 days after topping before the two new shoots show visible regrowth, and roughly a week until they grow at equal speed. Allow 5–10 days of recovery before flipping, and do the last top at least 7–10 days before 12/12. Stressed, root-bound or very young plants recover more slowly. - [My plant is too tall for my tent: what can I do?](https://genetixbay.com/knowledge/answers/plant-too-tall-for-tent.md): If your plant is too tall for the tent, bend it rather than cut it. In veg or the first two weeks of flower, supercrop or tie the tallest tops down and outward; later, bend and tie woody tops sideways. Raise or dim the light so tops get no more than about 1,200 µmol/m²/s, drop the pot off any riser, and next time flip at half the final height. - [What is schwazzing?](https://genetixbay.com/knowledge/answers/what-is-schwazzing.md): Schwazzing is an aggressive defoliation schedule that strips almost every fan leaf at the start of flower and again around day 21. Proponents say it pushes light into bud sites; no controlled cannabis trial shows it raises yield or cannabinoids. GenetixBay's position is tuck, don't pluck: strip within reason if you must, never on stressed plants or autoflowers. - [When should I stop training my plants?](https://genetixbay.com/knowledge/answers/when-to-stop-training.md): Stop training cannabis by technique. Do the last topping at least 7–10 days before the flip to 12/12. Finish hard LST bending and supercropping by flower week 2–3, when stems lignify at the end of the stretch. Keep tucking under a net for about the first 2 weeks of stretch. After that, only gentle guiding and support. - [Why are my buds airy or larfy?](https://genetixbay.com/knowledge/answers/why-are-my-buds-airy.md): Airy, larfy buds are usually buds that got too little light: lower and inner sites often receive a fraction of the canopy-top PPFD, well below the 800–1,200 µmol/m²/s flower target. Other causes are heat above about 30 °C (86 °F), harvesting too early, root-zone or feeding problems, and cultivars that naturally make loose flowers. Check light at the bud, not the top. ## Glossary - [Glossary index](https://genetixbay.com/knowledge/glossary/): 759 terms with synonyms, A–Z and by category - [Compact glossary](https://genetixbay.com/llms-glossary.txt): every term on one line, "Term (aka …): definition. URL" - [Glossary JSON](https://genetixbay.com/knowledge/api/glossary.json): every term, aliases, category, related terms and articles - [Bay Lines](https://genetixbay.com/knowledge/glossary/bay-lines.md): Bay Lines are GenetixBay's community breeding programme: lines bred from member-nominated keepers and documented males, tested and released with full records. - [Bay Trials](https://genetixbay.com/knowledge/glossary/bay-trials.md): Bay Trials are GenetixBay's member-run controlled grow experiments that test growing claims side by side and publish the results openly. - [Cultured Pearls](https://genetixbay.com/knowledge/glossary/cultured-pearls.md): Cultured Pearls are GenetixBay Pearls bought with money, usable only as store credit in the GenetixBay store; they never transfer between members. - [Evidence ladder](https://genetixbay.com/knowledge/glossary/evidence-ladder.md): The GenetixBay evidence ladder labels every growing claim as Established, Supported, Grower practice, Contested or Myth, according to how strong the evidence is. - [Evidence levels L0-L4](https://genetixbay.com/knowledge/glossary/evidence-levels-l0-l4.md): GenetixBay evidence levels rate lineage claims from L0 (unverified) through L1 community reported, L2 breeder reported and L3 documented to L4 lab-confirmed. - [Founding Member](https://genetixbay.com/knowledge/glossary/founding-member.md): A Founding Member is an early backer of GenetixBay who joins before launch, getting first access, a permanent badge and among the lowest numbers in the archive. - [GB-ID](https://genetixbay.com/knowledge/glossary/gb-id.md): A GB-ID is GenetixBay's permanent identifier, such as GB-GEN-0001842-6, for a genetic line, landrace, seed batch, plant, cut, grow, harvest, trial or document, so records never get lost or renamed. - [Herm threshold](https://genetixbay.com/knowledge/glossary/herm-threshold.md): The herm threshold is GenetixBay's two-tier herm standard: a 10-plant screening grow with zero herms to be featured, then about 150 or more community-grown plants before a line can be Verified under 2% herm rate. - [Jardin](https://genetixbay.com/knowledge/glossary/jardin.md): Jardin is GenetixBay's grow system in development: a controller and sensor kit for logging and climate control, with per-element custom nutrient dosing. - [Mythbusters](https://genetixbay.com/knowledge/glossary/mythbusters.md): Mythbusters is GenetixBay's page of growing myths and their verdicts, with open Bay Trials and finished results marked Busted, Confirmed or Inconclusive. - [Open research](https://genetixbay.com/knowledge/glossary/open-research.md): Open research is GenetixBay's approach of settling growing questions with member-run controlled trials and publishing protocols, data and verdicts for anyone to see. - [Pearls](https://genetixbay.com/knowledge/glossary/pearls.md): Pearls are GenetixBay's community points, in two kinds: Wild Pearls earned by contributing, and Cultured Pearls bought as store credit; neither has cash value. - [Professor Greenleaf](https://genetixbay.com/knowledge/glossary/professor-greenleaf.md): Professor Greenleaf is GenetixBay's character and botanical knowledge assistant, who answers growing and breeding questions from the cited knowledge base and the grower's own records. - [Seed Club](https://genetixbay.com/knowledge/glossary/seed-club.md): The Seed Club is GenetixBay's seed programme run through a licensed partner, offering tested seed lots with published batch records where the law allows. - [Stud Book](https://genetixbay.com/knowledge/glossary/stud-book.md): The Stud Book is GenetixBay's showcase of documented male plants, with selection journals, keeper details and sire credits; males are encouraged and rewarded. - [The Swap](https://genetixbay.com/knowledge/glossary/the-swap.md): The Swap is GenetixBay's pseudonymous, escrowed member-to-member exchange, reviving the Bay's 2009 peer-to-peer roots, running only in the modes local law allows. - [Wild Pearls](https://genetixbay.com/knowledge/glossary/wild-pearls.md): Wild Pearls are GenetixBay points earned by contributing, such as journals, males, preservation and trials; they can move between members but have no cash value. ## Optional - [Lab notes](https://genetixbay.com/blog/): build updates and grow science from the GenetixBay lab - [Fund the Bay](https://genetixbay.com/fund): founding rewards ## Français (fr-CA) French pages live on https://genetixbay.ca/fr/ (hreflang fr-CA); genetixbay.ca shows prices in CAD, genetixbay.com in USD. - [llms.txt en français](https://genetixbay.ca/llms-fr.txt): 10 translated articles (machine drafts in review) and 718 glossary definitions