Cannabis Training: LST, Topping, FIM, Mainlining and SCROG

Plant training means steering how a cannabis plant grows so that more of its tops get the same amount of light, instead of one tall main cola shading everything below it. If this is your first grow, our advice is to skip training for now. If you have a grow or two behind you, start with low stress training (LST): it is the gentlest method and the hardest to get badly wrong. Topping, FIMing, supercropping and mainlining come after that, and only on photoperiod plants. Training gives you more tops and a flatter canopy. It does not guarantee a bigger harvest, because genetics, light and care still decide most of that.

What plant training does

Left alone, a cannabis plant grows like a Christmas tree. There is one strong main stem with a big cola on top, and side branches that get less light the lower they sit. That shape comes from apical dominance: the growing tip at the top holds back the buds lower down the stem. A 2025 review on mainlining explains that cutting off that tip disrupts apical dominance and sets off hormonal and sugar-signalling changes, mainly around the plant hormone auxin, that wake up the side buds (Ijoma et al., 2025).

Bending works on the same idea without a cut. Pull the main stem sideways and the side shoots end up level with the old top. They then start growing upward as if they were the leader.

Why go to the trouble? Light. In a study on large medical cannabis plants of around 2.5 m tall, the flowers at the bottom had lower cannabinoid levels, and that matched the poor light reaching them. Removing lower leaves and branches to let light in raised the levels down there and made the plant more uniform (Danziger and Bernstein, 2021). That was research on big plants, not a home tent. The principle still holds: an even canopy makes better use of your light than a cone does.

Low stress versus high stress

Low stress training bends and ties the plant without wounding it. High stress training damages the plant on purpose. Topping and FIMing cut tissue away, and supercropping crushes the inside of a stem. High stress methods get a stronger response from the plant, but they cost recovery time, and every wound is a way in for disease. The same review points out that the repeated cutting in mainlining carries a risk of disease and infection.

Who should train, and who shouldn't

We advise beginners against training altogether. This is advanced growing. On a first grow you are still learning to water, feed and read your plant, and a training mistake on top of that makes it hard to tell what went wrong.

If you are just starting out, we would rather see you grow one or a few plants outdoors, if you have the space for it. Give the roots room with big pots or containers, or plant straight into open ground. Spring water and rainwater are best. If your tap water is high in chlorine, fill a barrel and use it the next day: the chlorine evaporates, and if the barrel stands inside, the water is at room temperature by then. Roots don't like cold water, and a cold shock sets plants back. There is more on this in the water and pH chapter of our grow guide, and in our piece on the cannabis root system. Strains that forgive a few mistakes are in our beginner-friendly seeds.

Which method should you pick?

• Autoflower: LST only, started early. We don't top autoflowers (more on that below).
• Photoperiod plant in a small tent or under a low ceiling: LST, maybe with one topping or a FIM. Or start with a plant that stays small, from our compact cannabis seeds for small spaces.
• Photoperiod plant where you want a flat canopy full of even tops: mainlining, SCROG, or the two together.
• A few branches shooting up too tall: supercropping.
• Not sure: LST. It is the one method that rarely ruins anything.

Low stress training (LST)

LST means bending stems and holding them in place with soft ties, so the plant grows wide instead of tall. Start in the vegetative stage, while the stems are young and bend easily. As soon as a stem is long enough to tie down, you can begin.

What you need

• Soft plant ties, plant tape or pipe cleaners. Never bare wire or a coat hanger, which cut into the stem as it thickens.
• Anchor points: small holes drilled around the rim of the pot, or stakes, or a frame around the plant.
• Tape, in case a stem cracks. Here is how to deal with broken stems.

How to do it

• Bend the main stem gently to the side and tie it to the rim of the pot.
• As the side shoots grow up, guide them outward and tie them as well, so the plant spreads out like a wheel.
• Check every day or two. Untie, move and retie as the plant grows. LST is not something you set and forget.
• Don't tie the plant to the floor or to anything that stops you moving the pot, and keep the base of the stem in view so you can check it.

What goes wrong most is a snapped stem. Bend in stages, a little further each day, rather than all the way at once. If you hear a crack or see a crease, stop, support the stem and give the plant a few days.

Our grower Mr. Sour shows LST step by step in these two videos.

Can you keep going once the plant flowers? Small adjustments early in flower are fine, for example pulling a branch into the light or opening up the middle for airflow. Older stems are stiffer and snap more easily, so be gentle, and leave the plant alone once the buds are really forming.

LST on autoflowers

Autoflowers don't wait for shorter days before they flower. Scientists call them photoperiod insensitive, and in 2022 researchers mapped the gene locus behind the trait and named it Autoflower1 (Toth et al., 2022). In practice, an autoflower runs on its own clock and has little time to recover from damage.

That is why we advise against topping autoflowers. They go into flower almost straight away, and topping can disturb that flowering. The mainlining review reaches a similar view: it calls autoflowering strains generally unsuitable for mainlining because of their short vegetative phase.

What does work is gentle LST, started early while the stem is still soft. Tie the main stem down once it is long enough, spread the side shoots out, and leave it at that. No cutting. If you want to try it, browse our autoflower seeds, and read up on pot size for autoflowers before you plant.

Topping

Topping means cutting off the main growing tip just above a node, the point where leaves and side shoots grow from the stem. The two shoots at that node then take over, so the plant grows two main tops where it had one. Top each of those again and you get four.

Let the plant grow several nodes first. A seedling is too small to recover from a cut.

Is there evidence it helps? One study on a CBD-type medical cannabis strain grown indoors compared plants with the main tip cut off, plants with their side shoots removed, and plants left alone. The topped plants made significantly more flower and leaf dry weight than the other two groups. Their total CBD yield, though, did not differ significantly from the untouched plants (Crispim Massuela et al., 2022). So topping gave more mass, not automatically more of what the growers were after. That is one strain under research conditions, so don't read it as a promise either way.

Topping without trouble

• Don't top too often. A plant you keep cutting spends its time recovering instead of growing.
• Work clean. Wear latex gloves or something similar, use clean, sharp scissors, and disinfect them when needed. Every cut is an open wound.
• Only top a healthy plant, and let it recover before the next round of stress.

FIMing, and FIM versus topping

FIM is short for "F*** I Missed". Instead of cutting cleanly below the newest growth, you pinch or cut through the top of that new shoot and leave part of it behind. A FIM can give more than two new tops, but how many varies from plant to plant, and the result is less predictable than topping.

How to choose between them:

• Topping is predictable. You get two tops, a clear structure and a good base for mainlining or SCROG.
• FIM takes away less of the plant and can give more tops, but you can't control the result as well.
• Want control? Top. Want lots of tops and don't mind some unevenness? FIM.
• On autoflowers, neither.

Supercropping

Supercropping is high stress training where you injure a stem on purpose. The mainlining review describes it as deliberately injuring the stem to encourage thicker branch growth. You squeeze the stem between thumb and finger until the fibres inside give way, then bend it over. The skin outside stays whole. Over the following days the plant repairs the spot and a thick knuckle forms there.

It is a handy fix for a branch that has grown too tall and is getting too close to the lamp, and a way to bring a tall plant's tops level with the rest.

How to supercrop

• Choose a branch that is still green and soft. Late in the vegetative stage or early in flower is the usual time.
• Squeeze and roll the stem gently between thumb and finger, a little at a time, until it feels soft.
• Bend it over slowly. If it droops a lot, tie it for support. It normally lifts itself back up within days.
• Not sure how far to go? Bend in stages, a bit further each day.

The risks are a split stem and an open wound. If the skin tears, tape it and keep it clean, because in a damp grow room a wound invites mould. Don't supercrop late in flower, when the plant has no time left to heal.

Mainlining (manifolding)

Mainlining builds a symmetrical plant on purpose: one short trunk that splits into a "manifold" of equal branches, each ending in a cola of about the same size. It combines topping, removing lower growth and tying down. The review by Ijoma et al. (2025) notes that much of what is known about it comes from blogs and growers' own experience, and that the science behind it is still limited. The steps below follow the practice that review describes.

• Wait until the plant has about 5–6 nodes.
• Cut the main stem back to the third node from the base, and remove all growth below that third node.
• Give the plant about five days to recover.
• Tie the two remaining branches down flat. Once they have grown a few nodes, top each of them again, so every branch splits into two.
• Repeat. One topping gives two colas, two give four and three give eight. The review describes topping 3 or 4 times in the vegetative stage, for 8 or 16 colas.
• Then switch the light from 16 hours on and 8 off to 12 on and 12 off to start flowering.

The cost is time. The review lists delayed flowering of around two weeks as a downside, and all that cutting means hygiene matters even more than with a single topping. It is not for autoflowers. For the full method, read our guide to mainlining cannabis.

SCROG, the screen of green

SCROG uses a flat net or screen stretched above the plants. As shoots grow through it, you tuck them back under and push them sideways, so the canopy fills the screen evenly. Think of it as LST with a frame doing the holding. According to the mainlining review, growers often add a screen to a mainlined plant to support the flowering manifold.

• Hang the screen low enough that the plant reaches it during the vegetative stage, and high enough that you can still work underneath.
• Keep tucking shoots under and outward until most of the screen is filled.
• Switch to flower before the screen is completely full, because plants keep growing for a while after the switch.
• Clear out weak growth under the screen. It sits in the shade and won't make much.

Because SCROG is about filling a space with as many good tops as possible, it pairs well with high yielding cannabis seeds.

Defoliation and lollipopping

Lollipopping means removing small shoots and leaves low on the plant that won't get enough light to make decent buds. Defoliation means taking off fan leaves that shade bud sites. In the study on tall plants above, opening up the lower plant helped. But the evidence is mixed: in the topping study, plants with their side shoots removed did no better than untouched plants.

So take a little at a time and never strip a plant bare. Leaves are where the plant makes its food. The pruning, topping and supercropping chapter of our grow guide covers this too.

Mistakes we see most

• Topping too much. More cuts don't mean more buds. Each one costs the plant recovery time.
• Dirty hands and tools. Use gloves and clean scissors, and disinfect them when needed.
• Bending too far in one go. Stems crack and snap. Bend in stages, a bit further every day.
• Topping autoflowers. They flower almost straight away, and topping can disturb that.
• Training on a first grow. Learn the basics first, then add training.

Combining methods

Most growers mix methods. LST plus a single topping is a common start. Topping or mainlining with a SCROG screen on top is a step further. Do the cutting early, while the plant is small, then let it recover before you tie it down. Save supercropping for fixing the odd branch that runs away later on. And give every high stress step its own recovery time before the next one.

An even canopy only pays off if your light covers all of it. Our grow guide's light and lamps chapter helps you check that.

Which seeds suit training?

Almost any photoperiod plant can be trained. Feminized seeds suit topping, mainlining and SCROG well, because every plant is female and you won't spend weeks shaping a male you then have to remove. Have a look at our feminized seeds or indoor cannabis seeds. One example is Chronic Feminized, a strain exclusive to AMS.

For autoflowers and gentle LST, there is Northern Lights XTRM Autoflower, which its product page describes as well suited to indoor growers, and Big Bud Autoflower, a medium-sized plant.