Cannabis Topping Guide: When and How to Top

Quick answer

Topping means cutting the main growing tip off a cannabis plant above a node. The plant answers with two shoots in place of one. Top when the plant has 4 to 6 nodes and at least 3 weeks of vegetative growth. Cut 1/4 inch above the node with sterilized scissors. Recovery takes 2 to 5 days.

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What topping does

Cannabis grows from one dominant tip. Auxin made at that tip suppresses the shoots below it. This is apical dominance. Remove the tip and the two growth points at the node below take over. Each becomes a main cola. The plant also sends more auxin to lower branches, so side shoots stretch.

how many times to top cannabis plants

When to top

• Nodes: 4 to 6 on the main stem.
• Age: 21 to 28 days from seed, or 10 to 14 days after transplant.
• Height: 8 to 12 inches.
• Health: green leaves, no mites, no nutrient lockout.
• Light: 18/6 or 20/4 veg schedule.

Do not top a plant that stalled from cold, root damage, or overwatering. Fix the cause first.

Cannabis Topping: Benefits and Drawbacks for Growers

How to top: steps

1. Wipe scissors with 70 percent isopropyl alcohol.
2. Find the newest node at the top of the plant.
3. Cut the stem 1/4 inch above that node.
4. Leave both small shoots at the node intact.
5. Return the plant to veg light. Keep LED panels 18 to 24 inches from the canopy.
6. Wait 5 to 7 days after new growth starts before the next cut.

How many times to top

Two to four cuts per plant in veg. Each cut doubles the top count: 1 to 2, 2 to 4, 4 to 8, 8 to 16. Past 16 tops in a 4x4 tent, lower colas sit in shade and come out thin. Most home growers stop at 8.

When not to top

• Autoflowers. The veg clock runs on a fixed timer. A topping stall of 3 to 5 days cuts final yield for most auto grows. Skip it, or top at the third node before day 21.
• Flowering plants. Day 1 of 12/12 to harvest is too late. New tops need 3 or more weeks to fill.
• Seedlings under 3 nodes.
• Plants with powdery mildew, spider mites, or dying leaves.

Topping vs FIM vs LST

FIM cuts about 75 to 80 percent of the new growth instead of the whole tip. It can produce 3 or 4 tops. LST bends stems flat with no cut and no recovery time. Topping gives 2 tops and a 2 to 5 day pause in vertical growth.

Aftercare

Water with plain water at pH 6.0 to 6.5 in soil for the first 3 days. Hold nutrient strength at the current level. Keep air at 70 to 80 F and humidity at 60 to 70 percent. Check the cut site at 48 hours. A white callus is normal. Brown mush means infection, so cut the tissue back to clean green stem.

Yield notes

Topping changes canopy shape, not the genetic ceiling of the plant. Controlled trials on topping in cannabis are rare. Most yield figures come from grower logs, not peer reviewed studies. A topped plant with an even canopy spreads light across the tent. A single cola plant puts one bud under the lamp and leaves the rest dim.