LST During Late Flower
Low-stress training after week 3 of flower is risky territory — here's when it helps, when it hurts, and how to do it without snapping colas.
Most training should be done in veg and the first two weeks of flower. By late flower, your plant is committed to the buds it has and stems are lignified. There's still a legitimate role for gentle tucking and support to expose lower bud sites to light, but bending main branches at week 5+ is more likely to stress the plant or break a cola than to grow you a bigger harvest. Use it as light management, not as yield magic.
What it is
Low-stress training (LST) is the practice of bending and tying branches to change canopy shape without cutting. Standard LST is done in vegetative growth, when stems are flexible and the plant can recover and redistribute hormones [1]. 'Late-flower LST' refers to any bending, tucking, or repositioning done after roughly week 3 of the flowering stretch, when buds are forming and stems have lignified.
At this stage you are not really 'training' the plant anymore — you are doing canopy management. The plant has already set its bud sites and committed its energy. What you can still influence is how much light each bud gets and whether tall colas tip over under their own weight.
Why growers use it
Three legitimate reasons to touch a flowering plant:
- Light penetration. Buds receive light roughly according to the inverse square of distance from the lamp, and lower buds in a dense canopy can be severely shaded [2]. Gently moving a fan leaf or tucking a side branch can meaningfully change how much PPFD reaches a lower cola.
- Structural support. Heavy colas snap. Tying a leaning branch to a stake is LST in the loosest sense and is almost always worth doing.
- Evening out canopy height. If one cola is racing ahead and burning under the light, lowering it can prevent light stress.
What late-flower LST will not reliably do: dramatically increase yield, change cannabinoid content, or 'wake up' dormant bud sites. Claims that aggressive late training boosts harvests by 20–30% are folklore Anecdote. By week 4 of flower, the plant's yield ceiling is largely set by genetics, light, and what you did in veg.
When to start (and when to stop)
A rough timeline for an 8–9 week flowering photoperiod strain:
- Weeks 1–2 of flower (stretch): Full LST still works. Stems are flexible, the plant is growing fast. This is your last good window for real training [1].
- Week 3: Gentle bending only. Stems are stiffening. Tucking large fan leaves is fine.
- Weeks 4–5: Tucking and tying for support only. No new bends on main branches.
- Week 6 onward: Hands off except to add stakes or netting under heavy colas. Stop defoliation and stop repositioning.
- Final 2 weeks: Do not touch the plant beyond watering. Trichome heads are fragile and stress at this stage can affect terpene retention Weak / limited[3].
Autoflowers compress this timeline. Because they can't be revegged and have a shorter life cycle, late-flower training is even more risky and the conservative cutoff is week 2–3 of flowering.
How to do it (step-by-step)
1. Assess before you touch. Look at the canopy from the side. Identify (a) any cola leaning dangerously, (b) any lower bud sites completely shaded, (c) any cola so close to the light it's bleaching.
2. Stake heavy colas first. Push a bamboo stake or wire tomato cage into the medium next to a leaning branch. Use soft plant ties or velcro strips — never bare wire or zip ties against the stem. Tie in a figure-8 so the stem can flex without abrading.
3. Tuck, don't bend. For light penetration, move a fan leaf aside and clip it back with a soft tie rather than bending the branch underneath. Leaves are far more forgiving than lignified stems.
4. If you must bend a branch, do it incrementally. Wrap your hand around the stem and apply slow, steady pressure for 10–20 seconds before tying. You will sometimes hear a soft crack — that's the outer fibers giving. If it's a clean snap, see step 6.
5. Use a ScrOG net if you planned ahead. A horizontal trellis installed before week 2 of flower lets you weave branches under netting without bending stiff stems later [4].
6. Repair breaks immediately. If a branch snaps but is still attached, splint it with a stake and wrap with electrical tape or plant tape. Cannabis stems can heal partial breaks within a week or two if the cambium stays in contact Anecdote. A fully severed cola can sometimes be salvaged as a 'live harvest' if it's mature enough, but quality is usually reduced.
Common mistakes
- Bending stiff stems without warming them up. Lignified stems crack. If you must bend, do it slowly and accept that some will break.
- Aggressive defoliation framed as 'training.' 'Schwazzing' or heavy mid-flower stripping is popular online but evidence for yield gains is anecdotal and inconsistent Disputed[5]. Removing too many fan leaves in late flower removes the plant's sugar factories at the worst time.
- Repositioning the whole plant. Rotating pots is fine. Tipping the plant on its side to 'train' a cola away from the light is a good way to break the main stem.
- Training in the last two weeks. Stress this late can reduce terpene quality and provides no yield benefit because bud weight gain is nearly complete Weak / limited.
- Ignoring humidity. Damaged tissue in late flower under high RH is a bud rot invitation. If you bend or break anything, watch the wound site for botrytis [6].
Related techniques
- ScrOG (Screen of Green) — the planned version of late-flower canopy management; the net does the work for you.
- Defoliation timing — when to remove leaves and when not to.
- Supercropping — controlled stem crushing, almost always a veg-stage or early-flower technique.
- Lollipopping — removing lower growth before flower so you don't need to manage shaded buds later.
- Bud support and yo-yos — the safest 'late-flower LST' is just holding heavy colas up.
Sources
- Book Cervantes, J. (2015). The Cannabis Encyclopedia: The Definitive Guide to Cultivation & Consumption of Medical Marijuana. Van Patten Publishing.
- Peer-reviewed 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.
- Peer-reviewed Booth, J. K., & Bohlmann, J. (2019). Terpenes in Cannabis sativa – From plant genome to humans. Plant Science, 284, 67–72.
- Peer-reviewed Danziger, N., & Bernstein, N. (2021). Plant architecture manipulation increases cannabinoid standardization in 'drug-type' medical cannabis. Industrial Crops and Products, 167, 113528.
- Peer-reviewed Folina, A., Kakabouki, I., Tourkochoriti, E., Roussis, I., Pateroulakis, H., & Bilalis, D. (2020). Evaluation of the effect of nitrogen fertilization rates and defoliation on the growth of industrial hemp. Notulae Botanicae Horti Agrobotanici Cluj-Napoca, 48(4).
- Government Punja, Z. K. (2021). Emerging diseases of Cannabis sativa and sustainable management. Health Canada / Pest Management Centre research summary; published in Pest Management Science, 77(9), 3857–3870.
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