How to Top and Prune a Weed Plant: Topping, LST, Lollipopping and Defoliation

Pruning cannabis plants: the methods at a glance

Not every method suits every plant. The table shows when to use each one, how much stress it puts on the plant and whether it is suitable for autoflowers.

For a first grow, two methods are usually enough: LST for a flat canopy and a little lollipopping before flowering. Topping is the next step once your plants are healthy and growing vigorously.

Topping: how to top a weed plant

When you top a cannabis plant, you cut off the tip of the main stem. The plant then sends its energy into the two shoots directly below the cut — one main top becomes two. Repeat this on the new tops and you get four, then eight main colas.

When to top weed plants

The best time to top a cannabis plant is when it has 4–6 leaf pairs — usually in week 3–5 of the vegetative stage. By then it has enough roots and leaf mass to recover from the cut quickly. What the plant looks like at this age is shown in our guide to the cannabis seedling stage week by week.

How to top a pot plant step by step

• Tools: small, sharp, clean scissors — wipe them with alcohol first.
• Where to cut: directly above the 3rd to 5th node, so that the two side shoots at that node stay undamaged. A node is the point where leaves and side shoots grow from the stem — see our guide to cannabis plant parts.
• Afterwards: the plant needs about a week to recover. Don’t transplant it or feed heavily during that time.
• Topping again: only once the new shoots have formed 2–3 leaf pairs of their own.

Every topping adds a few days to the vegetative stage. With photoperiod strains that is not a problem, because you decide when flowering starts. Autoflowers, on the other hand, miss those days later on (see below).

Tip: strong shoots you remove from a photoperiod plant can also be rooted as clones — see our guide to cloning cannabis.

LST: low stress training

With LST (low stress training) you don’t cut anything off. You gently bend the main stem and side shoots to the side and fix them to the rim of the pot with soft, coated wire or plant ties. The tops then grow side by side instead of one above the other, and all of them get a similar amount of light.

• Start: from week 2–3 of the vegetative stage, while the shoots are still flexible.
• Technique: bend slowly, never snap. Better a little further each day than too much at once.
• Adjust: the tips turn back up towards the light within a day — re-tie them regularly.
• Goal: a flat, even canopy in which all tops are roughly the same distance from the lamp.

LST is the gentlest method and therefore the first choice for autoflowers, for small grow tents and for balconies where the plant shouldn’t get too tall. It combines well with a single topping.

What is lollipopping? Clear the bottom, harvest the top

When you lollipop a weed plant, you remove the weak side shoots and small leaves from the lower third. What is left are bare stems at the bottom and a dense canopy on top — the plant looks like a lollipop. The reason: under a lamp, very little light reaches the bottom of the plant. Only small, airy buds form there, and they still use up energy.

• When: just before switching to 12/12 or in the first two weeks of flowering, during the stretch.
• What can go: all shoots below the canopy that sit in the shade and won’t reach the light any more.
• What stays: the top two thirds of the plant with all its strong shoots.
• In two steps: better to prune once before flowering and once in flowering week 2 than everything at once.

Lollipopping pays off especially with photoperiod plants under a lamp. Outdoors, where the sun reaches the plant from all sides, it is usually enough to remove the lowest shoots close to the ground.

Cannabis defoliation: how much is right?

With defoliation you remove large fan leaves that cover bud sites or make the canopy so dense that hardly any air gets through. But fan leaves are also the plant’s power stations — so defoliate in moderation.

• When: just before the switch to flowering and, if needed, lightly around flowering week 3. After that, only remove sick or yellow leaves.
• How much: per round, only as many leaves as it takes for the plant to look visibly more open, but never bare — as a guide, no more than about a fifth of the leaf mass.
• Which leaves: large fan leaves lying directly over a bud site or growing into the centre of the canopy. Young leaves at the growing tips stay.

Heavy defoliation during flowering is risky: stripping a flowering plant of most of its fan leaves takes away the energy the buds need to fill out. In flowering, remove only individual leaves.

Defoliation or removing side shoots?

Removing side shoots means cutting out whole small branches from the leaf axils rather than leaves — essentially what happens in the lower part of the plant when you lollipop. Defoliation, by contrast, only concerns leaves.

Other methods: FIM, supercropping and mainlining

FIM

With FIM you don’t cut the growing tip off completely as with topping, but only most of it — about three quarters of the young tip. This often produces more than two new tops, but the result is less predictable. The timing is the same as for topping.

Supercropping

With supercropping you squeeze a shoot that has grown too tall between your fingers until the inside gives way, then bend it to the side. A thickened “knuckle” forms at that spot. The method works well against single shoots that are too tall, but it stresses the plant heavily — only in the vegetative stage and only on healthy photoperiod plants.

Mainlining

With mainlining you top the young plant early and remove everything below, so that only two symmetrical main shoots remain. You top these again until you have a “manifold” with usually eight equally strong tops. It costs a few extra weeks of vegetative growth and some patience — suitable for experienced growers with photoperiod strains.

When to prune cannabis plants: the calendar

When is it too late to top? As soon as the plant has been switched to 12/12 — or an autoflower shows its first pistils — it is too late. A topped plant needs vegetative time to grow new main shoots. What happens in flowering week by week is explained in our guide to the cannabis flowering stage week by week.

Topping autoflowers and pruning them

Autoflowering seeds have a short, fixed vegetative stage of about 3–4 weeks. Every day the plant needs to recover from a cut is missing later in size and yield. That is why the following applies to autoflowers:

• LST: yes — the best method for autoflowers, from about week 2.
• Topping: at most once and only on a strong, healthy plant, by week 3 at the latest. If in doubt, leave it out.
• Defoliation and lollipopping: only lightly and in small steps — remove a few large fan leaves that shade bud sites rather than stripping the plant.
• Supercropping and mainlining: no.

Outdoors: pruning against mould

In a wet autumn, mould is the biggest threat to outdoor plants. A dense canopy dries only slowly after rain and morning dew — exactly where bud rot sets in. Targeted pruning helps:

• Remove the lowest shoots: everything close to the ground that gets splashed and hardly sees the sun.
• Thin out the canopy: remove individual fan leaves inside the plant so the wind can blow through it.
• LST instead of height: a wide, open plant dries faster than a tall, dense bush.

How to spot mould early is covered in our guide to bud rot and cannabis mould. Strains that finish before the autumn rains are listed under outdoor cannabis seeds.

Common pruning mistakes

• Topping too early: before the 4th leaf pair the plant lacks reserves and stalls for a long time.
• Too much at once: topping, defoliating and transplanting in the same week overwhelms any plant.
• Stripping the plant bare: without fan leaves, there is no energy left for the buds.
• Heavy cuts in flowering: from flowering week 3, prune lightly only.
• Blunt or dirty scissors: they crush the tissue and open the door to disease.
• Training sick plants: fix the problem first, then prune.

If you are just starting out, you will find the whole process from seed to harvest in our guide how to grow cannabis.

Strains that respond well to training

Vigorous photoperiod strains with sturdy side shoots are well suited to topping and LST. For example Kukulkan (Black Domina × Chronic, up to 950–1,000 g/1.5 m² under 720 W LED), Tutankhamon (AK-47 genetics, easy to grow, up to 900–1,000 g/1.5 m²) and Anubis (Somango × Wembley, up to 850–1,000 g/1.5 m²). All three are available as feminized seeds and come straight from the breeder — Pyramid Seeds has bred its own genetics since 2002 — with a germination guarantee and discreet shipping.