LST vs topping: which to use, how to do each, and what the research found

LST vs topping comes down to bend or cut. Low-stress training bends stems sideways and ties them down, so the main growing tip stays and the lower branches catch up. Topping cuts that tip off, which breaks what the University of Saskatchewan calls apical dominance and pushes the side shoots to grow into new main tops. Both turn a Christmas-tree plant into a wider, flatter canopy. In one 2022 indoor study, topped plants gave more dried flower than unpruned ones, though not significantly more CBD. That study did not test LST.

Pick LST if you want to avoid wounds or are growing an autoflower on a short clock. Top if you want a shorter, bushier plant and have a few weeks of vegetative growth to spare. Plenty of growers do both: top once, then tie the new shoots outward.

Last reviewed: November 2026.

LST vs topping: the difference in one table

Both techniques belong to vegetative growth. USask describes training as optional, done to control the shape and size of the plant and spread the canopy, and it shows the LST version: a branch bent nearly horizontal and held with a wire plant tie, so the lower branches turn upward toward the light. Topping is the cut version of the same idea, and our grower’s glossary defines the related terms such as FIM and supercropping.

How to do low-stress training

Step 1: start during vegetative growth, once the main stem and branches are long enough to bend without snapping.

Step 2: bend the main stem or a tall branch gently toward horizontal and fasten it with a soft plant tie anchored to the pot rim or a stake, the way the USask photos show.

Step 3: repeat with each branch that pokes above the rest, aiming for an even, flat canopy where every top gets similar light.

Step 4: check the ties every few days. Stems thicken quickly in veg, and a tie that was loose last week can cut in now. Move ties outward as the branches grow.

LST keeps working until the flip to 12 hours of light. After that, the stretch in early flower can undo some of your levelling, so leave headroom.

How to top a cannabis plant, and when it is too late

Topping is a single clean cut through the main stem just above a node, removing the growing tip. The two shoots at that node then grow up as new main tops. In the Massuela 2022 study, researchers topped rooted clones at the tenth node of the main stem, 27 days after planting, when the plants had 10 to 14 internodes, using disinfected clippers. You can top earlier on a smaller plant; what matters is that it is healthy and actively growing.

Clean the blade first. OSU Extension reports that hop latent viroid spreads on pruning tools through plant sap, and that bleach solutions inactivate it while ethanol and hydrogen peroxide do not. Clean between plants.

When is it too late to top? Once the plant is flowering. USask advises against pruning branches in early flower because it can cause extra stretching, so do your last topping before you switch the timer to 12 hours of light. A clone fresh from the store should settle in first; see our guide to a clone’s first two weeks.

Do you top autoflowers?

You can, but the timing is tight. USask’s flowering guide says autoflowers begin flowering after about four to five weeks of total growth regardless of light, and its vegetative guide puts their veg stage at three to five weeks. Any cut has to heal inside that window. LST removes nothing, which is why we would reach for ties first on an autoflower and save topping for photoperiod plants, where you control how long veg lasts.

Does topping increase yield?

Sometimes, and it depends on what you measure. Massuela and colleagues grew one CBD-dominant genotype indoors. Topped plants produced significantly more dried flower and leaf than unpruned plants and plants with their lowest branches removed, with more of the flower toward the top. Total CBD yield showed a trend of topped above control, but the difference was not statistically significant.

A 2021 greenhouse study by Danziger and Bernstein on tall high-CBD plants found that topping once did not significantly change flower yield, while a double prune, with a second cut at the switch to flowering, raised it. That second cut runs against the USask advice above, and those plants grew to about 2.5 meters, so it is a poor template for a tent. The fair summary is that topping reliably makes plants shorter and bushier, and yield gains vary.

For what to do with leaves and lower branches later in the grow, see our pruning guide; for the whole season, see how to grow cannabis at home. Plan the canopy around the legal plant count: Health and Safety Code section 11362.2(a)(3) allows not more than six living plants per private residence in California, kept in a locked space out of public view under (a)(2), and OLCC allows four per residence in Oregon. Training lets fewer plants fill the space. This is general information, not legal advice.

Frequently asked questions

Sources

• California Health and Safety Code section 11362.2
• OLCC: Recreational marijuana FAQ
• Massuela et al. 2022, Plants: Harvest time and pruning technique in medicinal cannabis
• Danziger and Bernstein 2021, Plants: Shape matters
• USask: Vegetative growth
• USask: Flowering
• OSU Extension: Hop latent viroid in hemp
• DCC: What's legal

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