Short answer
Topping removes the main growing tip of a cannabis plant directly above a node. The plant then grows two shoots from that node in place of one. Do it in the vegetative stage, after 4 to 6 nodes form. Use clean scissors and cut 1/4 inch above the node.
What you need
- Clean scissors or pruning snips
- 70% isopropyl alcohol
- A plant with 4 to 6 nodes, 12 to 18 inches tall
Steps
- Wipe the blades with 70% isopropyl alcohol. Let them dry.
- Count nodes from the base. A node is the point where a leaf pair meets the stem.
- Find the top node. It holds the newest leaf pair and the apical bud.
- Cut the stem 1/4 inch above the top node. One clean cut. Do not crush the stem.
- Leave the node itself intact. Two axillary buds sit at that node.
- Return the plant to its light schedule. Keep air temperature at 70 to 80 F.
- Look for two new shoots in 2 to 5 days.
- Top again after each shoot adds 2 to 3 nodes. Four cuts give eight main colas.
Timing
Top in the vegetative stage. Stop 2 to 3 weeks before you switch to a 12/12 light cycle. Plants need that window to recover. Topping during flower costs bud sites and adds stress.
What topping does
Apical dominance is the mechanism. The apical bud makes auxin. Auxin moves down the stem and slows axillary bud growth. Remove the tip and auxin at that point drops. Lower buds break and grow.
step by step cannabis topping instructions
Limits
Topping changes plant shape. It does not raise yield on its own. Branch count goes up. Light, root space, nutrients, and genetics set the ceiling. Plants with low vigor and autoflowering plants do not recover from the cut. Skip topping on weak plants. Data on yield gain from topping alone in cannabis is thin. Most numbers come from grower reports, not controlled trials.