Cloning Techniques
Asexual propagation to create genetically identical plants from a healthy mother.
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Cloning is straightforward and works with basic tools — clean blade, rooting medium, humidity, and patience. You don't need expensive proprietary domes or gels; plain water works. But clones copy everything, including pathogens like Hop Latent Viroid. Tool sterilization between mothers is non-negotiable if you're working with multiple plants. It's the single most cost-effective way to preserve a good phenotype indefinitely.
What Cloning Is
Cloning is asexual propagation: you cut a branch from a living cannabis plant, induce it to grow roots, and end up with a new plant that is genetically identical to the donor (the 'mother'). Because cannabis is dioecious and highly heterozygous, seeds from the same cross produce plants with noticeably different traits. Clones do not — barring rare somatic mutations, a clone is the same plant as its mother Strong evidence[1].
This is why every named commercial cultivar you buy at a dispensary — GG4, Wedding Cake, Cherry Pie — exists as a clone line, not as seed stock. The 'cut' is the plant.
Why Growers Clone
Three practical reasons:
- Consistency. Every plant in the room finishes at roughly the same time with the same structure and cannabinoid profile. This matters for commercial uniformity and for medical patients who need reproducible effects Strong evidence[2].
- Speed. A rooted clone skips germination and early seedling fragility. You save roughly 2–4 weeks compared to starting from seed.
- Preserving a phenotype. When you pop a pack of seeds and find one standout plant ('the keeper'), cloning is the only way to keep that exact plant alive indefinitely. Once it flowers and dies, that genetic combination is gone unless you cloned it.
The trade-off: clones inherit any pathogens the mother has, including the increasingly widespread Hop Latent Viroid (HLVd). HLVd is transmitted almost entirely through infected cutting stock and contaminated tools Strong evidence[3].
When to Start
Take cuttings from a mother that is:
- In vegetative growth (18+ hours of light), not flowering.
- At least 4–6 weeks old with multiple lateral branches.
- Well-fed but not excessively high in nitrogen — very high tissue nitrogen can slow rooting Weak / limited[2].
- Free of visible pests and disease.
Many growers take clones 1–2 weeks before flipping the mother to flower, which gives the clones time to root while the mother finishes. If you plan to keep a dedicated mother plant, you can take cuttings every 2–3 weeks indefinitely as long as you let her recover between rounds.
How to Take a Clone: Step by Step
You need: a clean razor or scalpel, isopropyl alcohol to sterilize it, a rooting medium (rockwool cubes, peat plugs, or plain water), a humidity dome or clear container, and a weak light source (a single T5 fluorescent or low-wattage LED). Rooting hormone (gel or powder containing IBA, indole-3-butyric acid) is optional but improves success rates and rooting speed Strong evidence[2].
Steps:
- Prep the medium. If using rockwool, pre-soak cubes in pH 5.5 water for at least an hour. If using water, fill a clean cup with room-temperature, dechlorinated water.
- Sterilize the blade. Wipe with 70%+ isopropyl alcohol. Do this between every plant if you are taking from multiple mothers — this is the single most effective HLVd precaution Strong evidence[3].
- Select a cutting. Choose a healthy lower branch, 10–15 cm (4–6 inches) long, with at least 2–3 nodes. Lower branches typically root faster than apical tips Weak / limited[2].
- Cut at a 45° angle just below a node, using a clean slice rather than a crush. The angle increases surface area for water uptake and root initiation.
- Remove lower leaves. Strip the bottom 1–2 nodes so they can be buried in the medium. Trim the remaining fan leaves by roughly half to reduce transpiration load.
- (Optional) Dip in rooting hormone. A 1–2 second dip in IBA gel on the cut end. Do not double-dip from the main container — pour out a small working amount to avoid contaminating the bottle.
- Insert into medium. Push the stem into the rockwool cube or plug so the lowest node is buried. For water cloning, simply submerge the bottom 2–3 cm.
- Cover with a humidity dome or clear container. Target 70–90% humidity, 22–25 °C (72–77 °F), and low light (~100–200 µmol/m²/s, or a few inches under a fluorescent). High light at this stage stresses unrooted cuttings.
- Vent and mist once a day for the first 3–4 days. After day 4, gradually reduce humidity by cracking the dome open longer each day.
- Wait. Roots typically appear in 7–14 days. Do not pull on the cutting to 'check.' When you see white roots emerging from the bottom of the cube — or floating in the water — it is ready to transplant.
Common Mistakes
- Overwatering rockwool. Saturated, oxygen-starved cubes are the most common killer. Cubes should be moist, not dripping.
- Too much light. Cuttings have no roots to support photosynthesis. Bright light just dehydrates them. Dim light and high humidity are the recipe.
- Not sterilizing tools. Spreads pathogens between mothers. HLVd in particular is mechanically transmitted by contaminated blades Strong evidence[3].
- Taking clones from flowering plants. It can work ('monstercropping'), but rooting is slow and the resulting plants often show unusual growth patterns for weeks Anecdote.
- Poor mother health. A nitrogen-deficient, pest-stressed, or root-bound mother produces weak clones. Fix the mother first.
- Relying on unproven folklore. Honey, willow water, aspirin, and aloe are popular DIY rooting aids. While some contain trace plant hormones, controlled comparisons against commercial IBA products show marginal or no improvement over plain water Weak / limited[4].
Related Techniques
- Mother plant management. Maintaining a dedicated mother in permanent vegetative growth to supply continuous cuttings.
- Tissue culture (micropropagation). Lab-based cloning from meristem tissue. The main advantage is the ability to produce viroid- and virus-free plants; meristematic tissue can sometimes be cleaned of HLVd, which is impossible with standard cuttings Strong evidence[5].
- Aeroponic and misting cloners. Bare-stem cuttings suspended in air, sprayed with oxygenated water. Faster rooting (often 5–7 days) at the cost of equipment complexity.
- Re-vegging. Forcing a harvested flowering plant back into vegetative growth. Sometimes used to rescue a phenotype that was never cloned before flowering.
Sources
- Peer-reviewed Lata, H., Chandra, S., Khan, I. A., & ElSohly, M. A. (2009). Propagation through alginate encapsulation of axillary buds of Cannabis sativa L.—an important medicinal plant. Physiology and Molecular Biology of Plants, 15(1), 79–86.
- Peer-reviewed Caplan, D., Stemeroff, J., Dixon, M., & Zheng, Y. (2018). Vegetative propagation of cannabis by stem cuttings: effects of leaf number, cutting position, rooting hormone, and leaf tip removal. Canadian Journal of Plant Science, 98(5), 1126–1132.
- Peer-reviewed Bektaş, A., Hardwick, K. M., Waterman, K., & Kristof, J. (2019). Occurrence of hop latent viroid in cannabis sativa with symptoms of cannabis stunting disease in California. Plant Disease, 103(10), 2699.
- Peer-reviewed Davies, P. J. (Ed.). (2010). Plant Hormones: Biosynthesis, Signal Transduction, Action! (3rd ed.). Springer.
- Peer-reviewed Adhikary, D., Kulkarni, M., El-Mezawy, A., Mobini, S., Elhiti, M., Gjuric, R., Ray, A., Polowick, P., Slaski, J. J., Jones, M. P., & Bhowmik, P. (2021). Medical cannabis and industrial hemp tissue culture: present status and future potential. Frontiers in Plant Science, 12, 627240.
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