This board is for growers who already have a working grow room. The topics here are about shaping the plant, not just feeding it. They cover cutting the growing tips, bending stems, spreading plants under a net, removing leaves, and keeping mother plants for cuttings.
Why train a plant at all
A cannabis plant left alone puts most of its energy into one main top. Your lamp lights the whole floor, but much of that light falls on empty space around that single top. Training spreads the growth out, so more tops sit in good light.
Every method on this board solves that same problem. Your choice of method depends mostly on two things. The first is how much time you can spend on each plant. The second is how many plants your room is allowed to hold.
Two things decide whether training helps you or costs you a harvest. The first is timing against the stretch. The second is how you handle leaf removal. Both have their own section below.
The main methods in plain words
The canopy is the top layer of leaves and buds that catches the light. Every method below changes the shape of that layer.
| Method | What you actually do | Plant count and time | Full guide |
|---|---|---|---|
| Topping | Cut off the main growing tip. The plant then grows two main tops instead of one. | Fewer plants; the plant needs time in vegetative growth to recover from the cut. | Topping, FIM and mainlining guide |
| FIM | Pinch off most of the growing tip, but not all of it. This usually gives several new tops. | Similar to topping. | Same guide as topping |
| Mainlining | Top the plant several times and train the branches evenly, so it ends with a set of equal tops. | Few plants; the most vegetative time and hand work. | Same guide as topping |
| LST (low stress training) | Bend stems down and tie them, without breaking anything. The tops spread out to the same height. | Works with any plant count. Nothing is cut, so the plant has no wound to recover from. | LST, HST and supercropping guide |
| HST (high stress training) | Damage the plant on purpose to slow the tallest tops. Supercropping is the most common way to do it. | Few to medium plant count; the plant needs recovery time. | Same guide as LST |
| Supercropping | Squeeze a stem between your fingers until the inside goes soft, then bend it over. The outer skin stays whole. | Same as HST. | Same guide as LST |
| SOG (sea of green) | Grow many small plants with a short vegetative stage. Each plant grows mainly one top. | Many plants, little time per plant. | SOG vs SCROG guide |
| SCROG (screen of green) | Grow a few plants and spread their branches under a flat net, so all tops reach the same height. | Few plants, a longer vegetative stage, regular hand work. | Same guide as SOG |
| Defoliation | Remove some leaves so light reaches the buds lower down. | Any plant count; the risky part is getting the amount and timing right. | Defoliation guide |
How to choose. Start from your plant limit and your time. If your room may hold many plants and you have little time for each one, SOG fits. If you may hold only a few plants, SCROG or mainlining lets each plant fill more of the space. If you have never trained a plant, start with LST. It removes nothing, so a mistake costs you little.
Translator’s note: Before you plan an SOG room, check whether your licence limits how many plants you may grow. Read the conditions on your own licence to see whether they limit plant numbers or growing area. The forum’s licensing guide explains which licence covers which activity.
Translator’s note: Outdoors in Thailand, day length stays close to 12 hours all year. Photoperiod plants (plants that start flowering when nights get long) can therefore start flowering early, which leaves you less time to train them. See why photoperiod plants flower early in southern Thailand. If your vegetative time is short, choose LST or a single topping over mainlining.
Timing against the stretch
The stretch is the fast gain in height after you switch the plant to its flowering light schedule. The stretch guide covers it in detail.
Timing against the stretch decides almost everything in training. If you cut or bend a plant too late in the switch to flowering, it has no time to recover. So the heavy cutting and bending belong in the vegetative stage. The stretch guide gives the exact cut-off points.
The size of the stretch depends mostly on the strain’s genetics. You cannot change it much with technique. So you need to know how much your own strain stretches.
What to do on your next run:
- Measure the height of each plant on the day you switch to the flowering schedule.
- Measure again when the plants stop growing taller.
- Write down both numbers for each strain.
The purpose is planning. On the next run with that strain, you will know when to stop training and how much space to leave under the lamp.
Translator’s note: In Thai rooms at 30–35 °C, or after a power cut has let the room overheat, the plants are already under stress. Do not top, supercrop or bend hard on those days. Wait until the room is back to normal and the plants are well watered, so the extra stress does not add to the heat stress.
Defoliation: the most argued-about method
Defoliation causes more argument on this board than any other method. The reason is simple: there is little good evidence for or against it.
Leaves turn light into food for the plant. When you remove leaves, the plant can make less food. In return, more light reaches the buds lower in the canopy. That trade only pays off under specific conditions. The defoliation guide linked in the table above discusses when.
If you want to test it, use a side-by-side trial:
- Pick plants of the same strain in the same room.
- Defoliate half of them and leave the other half alone.
- Dry and weigh the harvest from each group separately.
The purpose is to find out whether defoliation pays in your room with your strain, rather than relying on someone else’s claim.
Translator’s note: In the Thai rainy season, a dense, leafy canopy holds damp air between the buds. That raises the risk of bud rot (Botrytis) and powdery mildew. Removing some leaves lets air move through the canopy. Each leaf you remove is still lost food, though, and many cuts at once stress the plant. Remove a few leaves at a time. Check your fans first, because poor airflow is often the real cause of damp air in the canopy.
Mother plants and clones
Underneath all these methods sits the cycle of mother plants and clones. A mother plant is a plant kept in vegetative growth permanently. You take clones (cuttings that grow roots and become new plants) from it. Methods like SOG need many identical plants, and clones from one mother give you that. The mother plants and cloning guide covers choosing, keeping and cutting mothers.
A lab-based alternative is tissue culture. This means growing new plants from tiny pieces of plant tissue in sterile containers. Check whether a lab in your area offers tissue culture for cannabis before you plan around it. If no lab is available to you, keeping your own clean mother plant is the practical option.
Translator’s note: Buying clones from another farm is a common shortcut, and a common way to bring in trouble. Clones can carry spider mites and thrips. They can carry hop latent viroid (HLVd), a viroid (a tiny plant pathogen) that often shows no symptoms at first. They may also turn out to be a different strain from the one you were sold. If you do buy clones, keep them in a separate area away from your main room. Check the leaves under a magnifier before they go in. Testing for HLVd needs a molecular lab test (RT-qPCR). Ask other growers in the B2B Services board whether a lab can run it for you.
A good first mother is a plant of a strain you have already grown and measured. Then you already know how it stretches and how it responds to training.
Where to start
- Read the stretch guide first. Measure the stretch of your strain on your next run, as described above. Everything else depends on that number.
- Try LST on one or two plants. The purpose is to learn how your strain bends and spreads, without cutting anything.
- Add topping in the vegetative stage once LST goes well. Note how many days each plant needs to recover. That tells you how much vegetative time to plan for.
- Choose SOG or SCROG from your plant limit and your time, using the table above.
- Test defoliation on half the plants only, and weigh the two halves separately.
- Keep one clean mother plant of a strain you have measured, so your next runs start from identical plants.
For a fixed schedule built on a mother and clone cycle, see two-room perpetual harvest.
Ask your question below
Post your training questions directly under this topic. Include the strain, room size, number of plants, lamp height, the method you used and the day you did it, plus photos of the canopy. With those details, other growers can tell you what to change.