Short answer. Tissue culture (micropropagation) means growing small plant pieces in sterile jars on a gel of nutrients, sugar and plant growth regulators. For cannabis its main uses are clean, space-saving clone banks and producing pathogen-tested stock. It is learnable at home, but most failures are contamination, and published protocols often work on only one or two cultivars [1].
What's happening
Plant cells can regrow shoots and roots when given the right nutrients and hormone balance. In culture there are no pests and little space needed, so hundreds of genotypes fit on a shelf. Monthony et al. (2021) reviewed the field and found important gaps: many studies used hemp as a stand-in for drug-type cannabis, tested one cultivar, or were not independently replicated [1] (Supported as a caution).
The stages
| Stage | What happens | Typical duration |
|---|---|---|
| 0. Mother prep | Clean, pest-free, tested mother; spray-free for a while | 2-4 weeks |
| I. Initiation | Surface-sterilise nodal segments or shoot tips; place on medium | 2-4 weeks |
| II. Multiplication | Shoots grow and are subdivided | 3-6 weeks per cycle |
| III. Rooting | Transfer to rooting medium (often auxin) | 2-4 weeks |
| IV. Acclimatisation | Move to plugs under high humidity, then harden off | 1-3 weeks |
Durations are indicative (Grower practice and [1][2]).
Media and conditions
| Factor | Common choice | Notes |
|---|---|---|
| Basal salts | MS (Murashige and Skoog) or DKW (Driver and Kuniyuki walnut) | DKW often reported to perform better for cannabis shoots (Supported, genotype dependent) [1] |
| Sugar | Sucrose ~2-3% (20-30 g/L) | |
| Gel | Agar ~6-8 g/L or gellan gum | |
| pH | ~5.7-5.8 before autoclaving | |
| Cytokinin (multiplication) | e.g., meta-topolin or BAP at low µM | Concentrations vary by protocol [1][2] |
| Auxin (rooting) | e.g., IBA | |
| Temperature | ~22-25 °C (72-77 °F) | |
| Light | ~16 h, low intensity ~30-60 µmol/m²/s |
These are typical ranges across published protocols; check the protocol you follow for exact valuesbeing reviewed.
Does it clean up HLVd?
Meristem (shoot-tip) culture combined with testing is a standard route for producing pathogen-free stock in many crops, and is used for cannabis. Viroids can be difficult to eliminate and success is not guaranteed; every plantlet must be tested before release [3] (Supported for the approach; elimination rates in cannabis are poorly documented)being reviewed.
Is it a perfect genetic freeze?
Nearly, but not perfectly. Somatic mutations occur in all dividing tissue [4], and culture can add some variation (somaclonal variation) depending on method. Slow-growth storage (lower temperature, fewer transfers) reduces the number of cell divisions (Supported in general plant TC) [1].
Safety
- Autoclaves and pressure cookers: follow the manufacturer's instructions; never open under pressure.
- Bleach (sodium hypochlorite) for surface sterilisation: gloves and eye protection; never mix with acids or ammonia.
- Ethanol (70%) and flame or bead sterilisers near each other are a fire risk. Keep ethanol closed and away from flames.
Common mistakes
- Starting from a dirty mother. Internal bacteria show up weeks later.
- Copying one paper's hormone recipe and expecting it to work on every cultivar.
- Skipping acclimatisation humidity: plantlets lose water fast in normal air.
- Calling tissue culture "virus free" without tests.
Evidence
- Feasibility and limitations of cannabis TC: Supported (reviews) [1][2].
- DKW vs MS for cannabis: Supported, genotype dependent [1].
- Viroid elimination through meristem culture: Grower practice / limited published data [3].
