# Topping vs LST: it depends on the cultivar, so test yours

> Topping and low-stress training (LST) both aim for a flat canopy of many tops in good light. The founder is personally against topping most of the time and prefers simple LST, because how a plant handles losing its tip is cultivar-dependent: some hazes lose heavy clone-taking without blinking, others crash from losing a limb. The research is thin: one controlled study on large greenhouse plants found pruning twice raised yield per plant, and canopy studies show even light raises cannabinoid uniformity. Run a split-clone test on your own cultivar.

- Canonical: https://genetixbay.com/knowledge/training/topping-vs-lst.html
- Category: Training · Level: Intermediate
- Evidence: Grower practice · Status: Draft: awaiting expert review
- Stage: Veg · Systems: Any system
- Updated: 2026-11-02 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Questions and answers

**Is topping or [LST](https://genetixbay.com/knowledge/glossary/lst.md) better?** Neither wins everywhere; it depends on the cultivar. Both create a [flat canopy](https://genetixbay.com/knowledge/glossary/even-canopy.md) with many tops in good light. LST does it without cutting, so there's no recovery time; topping breaks [apical dominance](https://genetixbay.com/knowledge/glossary/apical-dominance.md) faster but costs a few days. The founder is personally against topping most of the time and prefers simple LST. Test your cultivar with split clones.

**Why do some cannabis plants handle topping badly?** Cultivars differ in how they respond to losing their [growing tip](https://genetixbay.com/knowledge/glossary/apical-meristem.md) or limbs. In the founder's experience some [hazes](https://genetixbay.com/knowledge/glossary/haze.md) shrug off heavy clone-taking and cutting without slowing, while other cultivars stall or even die from the loss of a limb. Stress, small root systems and topping too young make it worse. Watch recovery speed on a test plant before topping a whole room.

**Does topping increase yield in cannabis?** Sometimes. In the one controlled study, on large greenhouse plants of a CBD-dominant medical cultivar, pruning twice raised flower yield per plant, with [cannabidiolic acid](https://genetixbay.com/knowledge/glossary/cbda.md) rising from 14.1 to 22.5 g per plant. Small indoor plants and high-THC cultivars weren't tested, and responses are cultivar-dependent. An even canopy in strong light is what drives yield.

**How do I test topping vs LST on my cultivar?** Take matching clones from one mother, root them together, then train half by topping and half by LST, with the same pots, light, feed and [veg time](https://genetixbay.com/knowledge/glossary/veg-time.md). Record days to recover, days to a full flat canopy, top-cola size and final [dry yield](https://genetixbay.com/knowledge/glossary/yield.md) per plant, and lab-test both if you can. Repeat once before trusting the result, and post it as a GenetixBay grow journal.

**What is LST?** Low-stress training bends and ties stems outward and down so the plant grows as a flat, even canopy without cutting anything. Side branches rise to meet the bent main stem, giving many tops at the same height under the light. It suits [autoflowers](https://genetixbay.com/knowledge/glossary/autoflower.md) and cultivars that recover slowly from cutting, and it pairs with a screen ([SCROG](https://genetixbay.com/knowledge/glossary/scrog.md)).

**Short answer, in plain words.** Topping (cutting off the top) and LST (bending and tying the plant down) chase the same thing: **lots of tops at the same height, all in good light**. LST gets there without cutting. The founder is **personally against topping most of the time** and prefers simple LST, because plants react to cutting very differently: some hazes lost heavy clone-taking "without blinking", while other cultivars crash or even die from losing a limb (founder's field experience) [6]. The research is thin, so the honest answer is: **it depends on the cultivar; test yours.**

> **Greenleaf says:** Tie it down first. You can always cut later, but you can't glue a top back on.

## What do topping and LST each do?

Both break the plant's habit of growing one [main cola](https://genetixbay.com/knowledge/glossary/cola.md). *Established (plant physiology).*

- **Topping** removes the growing tip. The tip makes auxin that suppresses the side buds below it (apical dominance); take the tip away and the two shoots below take over [5].
- **LST** bends the main stem sideways and down. The tip is no longer the highest point, so side branches rise to meet it, and the canopy flattens without a cut.
- **Why it pays:** light falls off down the canopy, yield follows light [4], and lower, shaded buds have lower [cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md) concentration [1]. A flat canopy puts more bud sites in strong light.

**Topping vs simple LST**
- **Topping** (Cut the tip)
  - Pro: Fast, predictable split into two main tops
  - Pro: Pairs well with SCROG
  - Con: Recovery time: days of slower growth
  - Con: Some cultivars handle losing tips or limbs badly (founder's field experience)
  - Con: Risky on stressed or small plants
- **Simple LST** (Bend and tie)
  - Pro: No cut, no recovery stall
  - Pro: Works on autoflowers and sensitive cultivars
  - Pro: Adjustable every few days
  - Con: Needs regular attention in veg
  - Con: Stems lignify; bend early
  - The founder's default most of the time.

## What does the research show?

Not much, and nothing comparing topping with LST directly. *Supported for canopy shape; grower practice for the comparison.*

- **Pruning can raise yield on large plants.** On large (about 2.5 m) greenhouse plants of a CBD-dominant medical cultivar, pruning twice was the only architecture treatment that raised flower yield per plant, with cannabidiolic acid rising from **14.1 to 22.5 g per plant** [1].
- **Opening the canopy evens out potency.** Removing lower branches and leaves let more light in and raised cannabinoid concentration in the lower buds, improving uniformity [1][2].
- **Density changes the answer.** Higher [planting density](https://genetixbay.com/knowledge/glossary/plant-density.md) increased yield per area but reduced cannabinoid uniformity, and architecture treatments interact with density [3].
- **No study has compared topping with LST,** or tested small indoor plants and high-THC cultivars the same way.

**The one controlled pruning result.** 14.1 → 22.5 g: CBDA per plant with pruning twice (Large greenhouse plants, one [CBD](https://genetixbay.com/knowledge/glossary/cbd.md) cultivar); 0: Controlled studies comparing topping with LST. Source: [1]

## Why is it cultivar-dependent?

Plants differ in how quickly they regrow from a cut and how much leaf and root they can afford to lose. In the founder's experience, some hazes kept growing through heavy clone-taking as if nothing happened, while other cultivars stalled for days or died after losing a limb (founder's field experience) [6]. Young, stressed or [root-bound](https://genetixbay.com/knowledge/glossary/root-bound.md) plants recover worse (see [recovery after topping](https://genetixbay.com/knowledge/answers/recovery-after-topping.md)).

## How do I test my own cultivar?

A split-clone side-by-side. *Grower practice; the method GenetixBay uses for every open question.*

**Topping vs LST, the split-clone test.** Matching clones: Same mother, rooted together → Same everything: Pot, light, feed, veg time → Half topped, half LST → Record: Recovery days, canopy days, top size, dry yield → Repeat once, then decide. Source: GenetixBay grow-journal method [6]

Record: days until regrowth after topping, days to a full flat canopy, top-cola size, dry yield per plant, and a lab test if you can. Post it as a GenetixBay grow journal so others growing the same cut can compare.

## Common mistakes

- Topping every cultivar by default without watching how it recovers.
- Topping young, stressed or root-bound plants.
- Topping after the flip, when recovery costs flowering time.
- Bending lignified stems hard and snapping them ([supercropping](https://genetixbay.com/knowledge/glossary/supercropping.md) is a deliberate technique; see [LST](https://genetixbay.com/knowledge/training/lst.md)).

## Sources

1. Danziger N, Bernstein N. 2021. Shape matters: plant architecture affects chemical uniformity in large-size medical cannabis plants. Plants 10(9):1834. https://doi.org/10.3390/plants10091834
2. Danziger N, Bernstein N. 2021. Plant architecture manipulation increases cannabinoid standardization in 'drug-type' medical cannabis. Industrial Crops and Products 167:113528. https://doi.org/10.1016/j.indcrop.2021.113528
3. Danziger N, Bernstein N. 2022. Too dense or not too dense: higher planting density reduces cannabinoid uniformity but increases yield/area in drug-type medical cannabis. Frontiers in Plant Science 13:713481. https://doi.org/10.3389/fpls.2022.713481
4. Rodriguez-Morrison V, Llewellyn D, Zheng Y. 2021. Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science 12:646020. https://doi.org/10.3389/fpls.2021.646020
5. Taiz L, Zeiger E, Møller IM, Murphy A. 2015. Plant Physiology and Development, 6th ed. (auxin and apical dominance). Sinauer Associates.
6. GenetixBay founder. Field experience (first-hand account; GenetixBay house position).