Cannabis Pruning and Training: LST, Topping, FIM and More

Left alone, a cannabis plant grows like a Christmas tree, one tall central cola shading a crowd of weak little branches below it. Pruning and training fix that by reshaping the plant into a wide, even canopy where many bud sites all catch strong light, which gives you more and bigger buds, better airflow, and a plant that fits your space and your lamp. The techniques cover gentle bending, cutting the growing tip, crushing and bending stems, and thinning leaves, and the skill is knowing which to use, when, and how much.

Key Takeaways

• Training reshapes the plant to catch more light and grow more colas. A wide, even canopy beats one tall stalk shading everything below it.
• It works by breaking apical dominance. The top bud suppresses the lower ones, and training releases them to grow.
• Bending is low stress, cutting is high stress. LST ties branches down without wounds, while topping, FIM, and super cropping wound the plant to redirect it.
• Do the heavy stuff in veg. Photoperiod plants recover during veg and should be healed before the flip, and autoflowers need a gentler hand.
• Restraint beats overdoing it. Research shows a couple of well-timed cuts can raise yield, while over-pruning can lower it.
• Clean tools and good timing matter most. Sterile scissors and the right growth stage protect the plant from stress and disease.

This guide walks through the main methods, LST, topping, FIM, super cropping, defoliation, and more, explains the plant science that makes them work, and takes you through the key ones step by step. At Barney’s Farm, decades of breeding produce vigorous plants that respond well to training, and a little shaping is how you get the most out of them.

Why Train a Cannabis Plant at All

The whole point of training is to control how the plant spends its energy and how light reaches it. Shoot branching is a major determinant of a plant’s architecture and directly affects its yield, and removing the shoot tip by pruning releases the lower buds to grow. By flattening and spreading the plant, you turn one dominant cola into a canopy of many, and several benefits follow at once. More bud sites sit up in strong light instead of being shaded out, the plant fits the height of your tent and the footprint of your light, the open structure lets air move through the canopy so mold has a harder time, and the buds finish more evenly. Dense-budded cultivars like Critical Kush especially benefit from the extra airflow that an open, trained canopy provides.

Apical Dominance: The Science That Makes It Work

Every training technique traces back to one piece of plant biology called apical dominance. The bud at the very top of the plant produces a hormone, auxin, that flows down the stem and holds back the lower side buds, which keeps the plant growing tall and narrow so it can outrace its neighbors to the light. Gardeners and growers use this to shape plants by pruning, because removing the stem tip takes away the auxin source and lifts its block on the lower buds, which then grow out into a bushier plant. Once you understand that the top is suppressing the rest, every method below makes sense, since each one is a way to weaken or redirect that dominance so the lower branches catch up.

Low-Stress Training (LST)

Low-stress training is the gentlest method and a good place to start. You bend the branches down and tie them in place without ever cutting the plant, which flattens the canopy and exposes the lower bud sites to light. Pulling the tall central stem over to the side also eases its dominance, so the lower branches grow up to meet it and you end up with an even, level canopy of many tops. Because there are no wounds, there is no recovery time, and LST works on both photoperiod plants and autoflowers. All you need is soft plant ties or coated wire and something to anchor to, like the rim of the pot or a few stakes.

How to LST a Plant, Step by Step

1. Start early in veg. Begin once the plant has several nodes and while the main stem is still young and flexible.
2. Bend the main stem to the side. Gently bend the top of the plant over toward horizontal and secure it with a soft tie to the pot rim or a stake.
3. Tie down the tall branches. As branches reach upward, bend the tallest ones outward so the whole canopy sits at an even height.
4. Retie as it grows. Adjust the ties every few days, spreading the branches to fill the space and keep the canopy flat.
5. Ease off by early flower. Make your last bends in the first weeks of flower, then let the buds develop undisturbed.

Topping

Topping is the classic high-stress technique. You cut off the growing tip above a node, which removes the top bud and its auxin, and the two buds waiting at the node below grow into two new main colas. Doing it again on each of those tops gives you four, then eight, and so on. Because one or two of the new tops will eventually take over and reimpose that dominance, growers repeat the process to build more colas. Topping is best done in veg on a healthy plant that has settled in, and it needs recovery time, so you finish topping a couple of weeks before you flip to flower.

How to Top a Plant, Step by Step

1. Wait for four or five nodes. Let the plant establish a bit before you cut, so it has the strength to recover.
2. Find the top growth tip. Locate the newest shoot at the very top of the main stem.
3. Cut cleanly above the node below it. With clean, sharp scissors, snip the stem just above the next node down, removing the top growth.
4. Let it recover and split. Over the next several days the two shoots at that node grow into two new main colas.
5. Repeat for more colas, then stop before flower. Top the new tops again once they add a few nodes, and finish all topping a couple of weeks before you switch to 12/12.

FIM, the Almost-Topping

FIM is a close cousin of topping with a looser touch. Instead of a clean cut through the node, you pinch off roughly three-quarters of the top new growth and leave the rest. That messier cut can push the plant to throw out four or more new tops from a single spot, instead of the two you get from topping. The name comes from a growers’ joke about a botched topping, and the technique keeps that rough-and-ready spirit. It puts a little less stress on the plant than a full topping and can bush the plant out faster, though the result is less tidy and predictable, so it suits growers who want more tops from one quick snip.

Super Cropping

Super cropping is a high-stress bending technique for when you need to fix the shape of a plant that is already growing. You gently pinch and roll a branch between your fingers to soften the stiff tissue inside without breaking the outer skin, then bend it over where it has gone soft. The plant heals the spot into a hard knuckle, the branch keeps growing while sitting lower, and its dominance gets redirected. It is a handy way to tuck a branch that is stretching above the canopy back down into the light. The honest caveat is that the evidence for super cropping boosting yield on its own is thin, so use it to correct geometry when you need to instead of as a routine every grow.

Defoliation and Lollipopping

Defoliation means removing select fan leaves so light and air reach the lower buds, and it is the technique growers argue about most. Done in moderation, in late veg and again after the stretch in early flower, it opens up a dense canopy. The key word is moderation. In one study on medical cannabis, pruning the plants twice during the grow was the best treatment for increasing yield, while heavier interventions either reduced yield or made no difference. Stripping too many leaves at once robs the plant of the solar panels it needs and sets it back, so you remove the leaves that are burying bud sites and leave the rest.

Lollipopping is a related cleanup that targets the bottom of the plant. You remove the lower, shaded growth and the small, wispy popcorn buds that never get enough light, so the plant pours its energy into the strong top colas instead of a scatter of weak ones. Those shaded lower sites tend to make airy, larfy buds anyway, so clearing them usually improves what you harvest, as long as you keep it moderate here too.

Screen of Green (ScrOG)

A screen of green, usually shortened to ScrOG, uses a trellis net stretched horizontally over the canopy. As the plant grows up into the net, you tuck the branches sideways through the squares to weave a flat, even layer of many colas that all sit at the same height under the light. ScrOG pairs naturally with LST and topping, and it is one of the best ways to fill the whole footprint of a single lamp with productive tops. You set the net a little above the canopy and do most of the weaving during the stretch, when the branches are growing fast and still easy to bend.

Mainlining, or Manifolding

Mainlining, also called manifolding, is a structured method that combines topping and low-stress training to build a symmetrical plant. You top the young plant down to a single node to create two equal shoots, tie those two down and out, then top each of them again to make four, and keep going until you have a set of eight or more colas that all branch from the same central hub and sit at the same height. Because every cola grows from an equal split, the plant sends its energy evenly to all of them, and the result is a manifold of uniform, chunky tops instead of one dominant cola surrounded by runts. It takes patience and adds veg time, so it rewards growers who like a tidy, repeatable structure and want an even canopy by design.

Combining Techniques for Best Results

In practice, few growers rely on a single method. A common approach is to top a plant to set up several main colas, tie those down with LST to keep the canopy flat, add a ScrOG net to hold the shape, and finish with light defoliation and lollipopping once flowering begins. Each technique handles a different job, so stacking them thoughtfully gives you the even, open, well-lit canopy that all of them are aiming for. The main rule stays the same, which is to space the work out and let the plant recover between rounds instead of hitting it with everything at once.

Timing and Safety

Timing separates training that helps from training that hurts. The high-stress methods like topping and FIM belong in veg, where the plant has time to recover and heal before flowering, and your last cuts should land a couple of weeks before the flip. Low-stress training is gentle enough to use throughout veg and into early flower. Super cropping fits late veg and early flower when you need to correct height, and defoliation works in late veg and after the stretch, though you avoid heavy leaf removal during the stretch itself. Autoflowers deserve special care, since they run on a fixed clock and cannot wait around to recover, so favor LST, keep any high-stress work minimal, and do it very early if at all. Two rules apply to all of it. Train only healthy, recently watered plants, and sterilize your scissors between plants, since plant sap on a dirty blade can spread viroids and disease.

Common Training Mistakes

Most training problems come from a short list of avoidable errors.

• Over-defoliating, which strips away too much of the plant’s photosynthesis and can cut your yield instead of raising it.
• Topping or heavy training too late, which stresses the plant deep into flower when it should be building buds.
• Training autoflowers too hard, which they cannot recover from in time because they flower on a fixed schedule.
• Using dirty scissors, which can carry viroids and pathogens from one plant to the next on the sap.
• Doing too much at once, instead of making a few cuts and letting the plant recover before the next round.
• Training a sick or stressed plant, which needs to get healthy first before it can handle any extra stress.

Frequently Asked Questions

What is the difference between LST and HST?

Low-stress training bends and ties branches without cutting, so there is no wound and no recovery time. High-stress training, like topping, FIM, and super cropping, wounds the plant to redirect its growth and needs time to heal. Many growers combine both.

Does topping actually increase yield?

Topping creates more colas and helps build an even canopy that catches more light. Research on cannabis shows that a couple of well-timed prunes can raise yield, though over-pruning can lower it, so the benefit comes from doing it in moderation and at the right time.

When should I top or train my plant?

Do high-stress work like topping in veg, finishing a couple of weeks before you flip to flower so the plant can recover. Low-stress training is gentle enough to use throughout veg and into early flower. Ease off heavy training once flowering is underway.

Can I train autoflowers?

Yes, but gently. Favor low-stress training, keep high-stress techniques to a minimum, and do any of it very early, because autoflowers run on a fixed clock and cannot wait to recover the way photoperiod plants can.

What is apical dominance?

It is the way the top bud of a plant suppresses the lower buds, using the hormone auxin to keep the plant growing tall and narrow. Training works by weakening or redirecting that dominance so the lower branches grow out and up.

How much can I defoliate?

Moderately. Remove the fan leaves that are shading bud sites or blocking airflow, but leave the plant plenty of foliage, since stripping too much at once stresses it and can reduce your yield.

Closing Thoughts

Training turns one tall cola into a wide canopy of many. You break apical dominance with gentle bends or well-timed cuts, do the heavy work in veg, go easy on autoflowers and on defoliation, and keep your tools clean. Done right, a few well-placed cuts and some patient bending give you more light, more airflow, and more bud from the same plant. Barney’s Farm genetics respond well to a bit of shaping, so train the plant to fill your space and let it reward the effort.

Barney's Farm has been developing premium cannabis genetics since the 1980s, with over 40 Cannabis Cup wins. Explore our full seed catalog and find strains bred for every climate and skill level.