How to LST and HST Cannabis: Low and High Stress Training

LST and HST are the two main ways growers shape a cannabis plant. LST, or low stress training, bends and ties stems without cutting anything, so the plant keeps growing with almost no downtime. HST, or high stress training, cuts or breaks plant tissue through methods like topping, FIMing, and super cropping, which stresses the plant but can build a wider canopy and more main colas. Knowing how to LST and HST cannabis correctly comes down to timing, clean tools, and giving the plant room to recover.

low stress training vs high stress training

What LST and HST Have in Common

Both approaches fight the same problem: a cannabis plant left alone grows one tall central stem, known as apical dominance. That single top cola hogs the light while lower branches stay small and airy. Training redistributes growth hormones so side branches catch up, which spreads light across more bud sites.

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The difference is damage. LST works with the plant's natural flexibility. HST removes or crushes tissue and triggers a repair response.

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• Recovery time: LST needs hours, HST needs days.
• Risk: LST rarely harms a healthy plant, HST can stunt a weak one.
• Best stage: both shine during vegetative growth, though gentle LST can continue into early flower.

LST Methods and How to Do Them

Bending and Tying

Wait until the plant has at least four or five nodes and the stems still flex. Pinch the stem between thumb and forefinger and roll it to soften the fibers, then lean the top outward and anchor it with soft plant ties, garden wire, or twine looped loosely around the branch. Never tie tight enough to cut into the skin.

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Screen of Green (SCROG)

A screen of green uses a horizontal net or trellis placed above the canopy. As shoots grow through the squares, tuck each one under and outward. The goal is a flat, even canopy where every top sits at the same height and receives similar light intensity.

Low Stress Defoliation

Plucking a few shaded fan leaves by hand counts as low stress when you remove only what blocks bud sites. Take a handful at a time rather than stripping the plant.

HST Methods and How to Do Them

Topping

Topping means cutting the main growing tip just above a node. Use clean, sharp scissors and leave a short stub above the node so the plant does not split. Two new shoots usually emerge from that node, turning one top into two.

FIMing

FIMing removes most of the new growth but leaves a sliver of the growing tip behind. The result is often four or more new tops instead of two. It is less predictable than topping, which is why some growers top instead.

Super Cropping

Super cropping bends a stem until the inner tissue crushes without breaking the outer skin. Pinch the spot you want to bend, roll it between your fingers until it feels soft, then fold it over at a gentle angle. The plant forms a knuckle at that point and the branch below it thickens.

Lollipopping and Heavy Defoliation

Lollipopping strips the lower third of the plant, where light rarely reaches and popcorn buds form. Heavy defoliation removes a large share of fan leaves at once and should be saved for a healthy plant in mid to late vegetation.

When to Train: Vegetative vs Flowering

Vegetative growth is the safe window for HST. A plant that is topped or super cropped during veg has weeks to rebuild before flowering starts, and it will fill the space you created. Once buds set, the plant stops stretching and puts energy into flower production, so cutting branches then costs you yield instead of building it. Gentle LST, such as tucking stems or tying down a tall shoot, can continue through the first two weeks of flower while stems still bend.

Step by Step: LST a Young Plant

1. Water the plant a few hours before training so stems are hydrated and flexible.
2. Decide the direction you want the main stem to lean, usually away from the center of the pot.
3. Soften the stem with a gentle pinch and roll between your fingers.
4. Anchor the top to the pot rim or a low tie point with soft, loose material.
5. Return every few days and tie down new shoots as they rise above the canopy.
6. Adjust ties as the stems thicken so nothing digs into the plant.

Step by Step: Top a Plant (HST)

1. Confirm the plant has at least four to six healthy nodes and no signs of stress.
2. Sterilize your scissors with rubbing alcohol.
3. Find the newest growth at the very top of the main stem.
4. Cut just above the node below it, leaving a small stub.
5. Leave the plant undisturbed for several days and watch for two new shoots.

Aftercare for a Stressed Plant

• Hold off on heavy feeding for about a week after HST so roots are not pushed while the plant repairs.
• Keep temperature, humidity, and light schedules steady rather than changing several variables at once.
• Skip further training on the same branch until new growth is clearly visible.
• Watch for slow growth, drooping, or pale new leaves and pause training if they appear.

Common Mistakes

• Training an unhealthy or overwatered plant that has no energy to recover.
• Topping too early, before the plant has enough nodes to support two new tops.
• Bending dry, woody stems that snap instead of flexing.
• Removing too many leaves in one session and shocking the plant.
• Leaving ties on too long so they cut into stems as they thicken.
• Super cropping late in flower, when stems have hardened and buds are already set.

LST vs HST at a Glance

• Choose LST for beginners, autoflowers, seedlings, and plants you want to keep low and even.
• Choose HST for vigorous photoperiod plants in veg, when you want more main colas and a wider canopy.
• Combine both by topping once or twice in veg, then using LST to spread the new tops across a screen.

The short answer to how to LST and HST cannabis is to train early, train in small steps, and let the plant tell you when it has recovered before you push it again.