Left alone, a cannabis plant grows like a Christmas tree: one tall main stem with a big flower on top and a skirt of side branches that get smaller and more shaded the lower they are. The top bud is the one in the photos; the dozen below it end up small and loose, because they spent the grow in the shade of the leaves above. Pruning cannabis, and training it, is mostly about one thing: getting light onto more of the plant than the tip.
For a first grow, you can leave the plant alone and still harvest. If you want to shape it, low-stress training is the gentlest start. Removing heavily shaded lower growth may help, but it is optional, and most of what the technique catalogues sell has never been tested in a trial.
What is low-stress training?
Low-stress training, usually shortened to LST, is bending stems over and tying them down so the plant grows sideways instead of up, without cutting anything. It is the safest place to start, because nothing is removed.
Start when the plant has four or five sets of leaves. Bend the main stem gently toward the rim of the pot and tie it there with soft ties; as the side branches turn upward toward the light, tie those out too, so the plant becomes a flat spread of equal tops. Add a tie every few days through the growing stage, and stop once flowering is under way.
The way not to snap a stem: bend a little at a time, over several days, rather than all the way at once. Bend young, flexible growth, not a stem that has gone woody. Support the bend with your fingers on both sides as you move it. If a stem creases anyway, tape it, leave it, and it will usually heal. We did not find a controlled trial of LST on its own; it is grower practice, and its purpose is plain: it spreads the branches and controls the height.
| Technique | What it is | Stress on the plant | Worth it for a first grow? |
|---|---|---|---|
| Low-stress training | Bending and tying stems sideways | Low | Optional; the gentlest to try |
| Topping | Cutting the main tip once so the plant forks | Moderate; a week to recover | Skip it the first time, or once at most |
| Lollipopping | Clearing heavily shaded lower growth | Low to moderate | Optional, where the lower growth is heavily shaded |
| Defoliation | Removing fan leaves to let light through | Moderate; contested | A few leaves, not a stripping |
| Super-cropping | Crushing a stem so it bends without breaking | High | No |
| Screen of green | Weaving branches through a net to make a flat canopy | Low, but fiddly | Later, once LST feels easy |
| Sea of green | Many small plants flowered early, no training at all | None | A different way of growing, not a technique to add |
When should I top my cannabis plant?
Topping is cutting off the growing tip of the main stem so the plant makes two main stems instead of one. Do it once, while the plant is still growing and has four to six sets of leaves, and not once it is flowering.
The point is a flatter plant with two or four tops at the same height instead of one tall one, so light reaches all of them evenly. The plant stalls for a week or so while it recovers, which is why you top early; topped in flower, it has little time to make up the loss. Skip it if the plant is already short and bushy, if it is sickly, or if it is an autoflower.
Growers say topping raises yield. In one CBD-type trial, topping increased flower weight, but the increase in total CBD was not statistically significant. In a trial on large plants, topping once made the flowers more even from top to bottom without changing the weight, and topping twice raised the weight. Take it as a shaping tool that does little harm, not a doubling of anything.
What is lollipopping?
Lollipopping is clearing the small branches and leaves from the shaded lower part of the plant, so it ends up bare-stemmed below and bushy above, like a lollipop. The growth down there makes small, loose flowers not worth drying; removing it sends the plant’s effort to the tops. There is no fixed line: take what is heavily shaded and leave what is not.
In the large-plant trial, removing the lower branches on its own did not make the flowers more even; it did when combined with removing fan leaves, and neither changed the weight of flower. Of the removals, the one that did was stripping off the main side branches, which cut yield by up to 99%. Lollipopping pairs with what our lighting guide says about light not reaching the lower buds; the alternative to lighting them is to not grow them.
Should I remove fan leaves during flowering?
A few, where they shade a flower; not many, and not the stripping some guides show. The big fan leaves are the plant’s solar panels, and a plant in flower is using them to fill the buds.
This is the most contested technique in home growing, with growers who strip plants bare in flower and growers who never take a leaf. The same large-plant trial found that removing fan leaves let more light down the plant and made the flowers more even from top to bottom, with no change in yield. The plain case for a light hand: take a fan leaf when it is covering a bud site, take leaves that are yellowing anyway, and otherwise leave them.
Outdoors, the reasons change
Outside, the sun moves and reaches the sides of the plant, so there is less need to flatten it. You train an outdoor plant mainly to control height, below a fence line or a neighbor’s view, and to keep it manageable. Support matters more than pruning: stake, cage or trellis a big plant before the branches are heavy and the autumn wind arrives. Timing follows the season: any topping by early summer, and no major cutting once the days shorten and flowering begins. Clearing crowded lower and inner growth also lets air through, which growers in damp climates do against mold; that is grower practice. Siobhan Darwish of Grow Sisters wrote her own guide to pruning and training in 2017, the field grower’s version of this page.
Can I prune autoflowers?
Bend, yes; cut, mostly no. An autoflower flowers on age rather than day length, so it runs on a short clock and has no spare weeks to recover from a topping. Low-stress training, started early and done gently, suits it well; topping and heavy defoliation usually cost more than they return. Our seeds vs clones page explains what autoflowers are.
Pruning cannabis in flower: when to stop, and what to cut with
Major reshaping ends before flowering: topping and heavy training belong to the growing stage. Early in flower, limited removal of shaded lower growth or a leaf that is shading a bud is fine; after that, leave the plant to fill out. Every cut is a wound that takes food and time to heal, and a plant in flower has less of both to spare; keep it fed and watered while it recovers, per our nutrients guide.
Clean the blade between plants, and clean it with bleach. Disease travels on tools, including the viroid that stunts plants and thins their flower, and a pair of scissors used on an infected plant will carry it to the next. In university extension lab tests, a one-in-ten solution of household bleach inactivated the viroid, while alcohol and hydrogen peroxide did not. No method is guaranteed, and all of them work worse on a blade with sap or debris on it, so wipe the blade clean first.
Updated November 2026: this article was rewritten by the editors as a plain-language training and pruning guide for home growers, with the research moved to the linked pages. Originally published 25 June 2021 by Lisa Rennie.
Image: Kindel Media, Pexels.
