Short answer
Top your cannabis plant when it has 4 to 6 healthy nodes and is still in the vegetative stage. That usually means 3 to 5 weeks from seed, or 2 to 3 weeks after a clone has rooted. Do it at least 1 to 2 weeks before you switch to a 12/12 flowering light schedule. Do not top autoflowers unless you are experienced and the plant is growing fast in its first 2 to 3 weeks.
Prerequisites
- Plant has at least 4 true nodes, or pairs of branches.
- Plant is healthy: green leaves, firm stems, no pests, no nutrient burn.
- Plant is in veg, not flowering.
- You have clean, sharp scissors or pruning shears.
- You can leave the plant undisturbed for 3 to 7 days after the cut.
When to top
- Wait for the 4th to 6th node. Earlier than 3 nodes stresses small plants. Later than 8 nodes wastes growth you could have redirected.
- Check the calendar. Count back from your planned flower flip. Top at least 10 to 14 days before that date.
- Confirm the plant is actively growing. New leaves should be opening every few days.
- Sterilize your scissors with rubbing alcohol.
- Cut the main growth tip just above the node, leaving a short stub. Do not crush the stem.
- Stop. Let the plant recover. New shoots will emerge from the node below the cut.
- Resume normal watering and feeding. Do not top the same spot again.
When not to top
- During flowering. Topping in flower removes bud sites and stalls development.
- On a sick, drooping, or pest-infested plant.
- On seedlings with fewer than 3 nodes.
- On autoflowers in most cases. Their veg window is short, and stress can shrink yield.
- Within 1 to 2 weeks of the 12/12 flip. The plant needs time to redirect growth.
Timing around flowering
The last topping should happen 10 to 14 days before you flip to 12/12. That gives the plant time to heal and push energy into the two new colas. If you top later, the plant may enter flower with uneven branches and smaller tops. For autoflowers, top only if the plant has 4 nodes by day 14 to 21 from sprout, and skip it if growth is slow.
Aftercare and follow-up topping
After the cut, keep light, temperature, and watering steady. Recovery takes about 3 to 7 days. Once the new shoots have 2 to 3 nodes, you can top those branches if you want more colas. Each topping needs its own recovery period. Stop all topping when pre-flowers appear or when you switch to 12/12.