Topping vs. FIMming, and when to stop
Topping gives you a predictable, even canopy. FIMming gives you more sites for less recovery time. Either works, the deadline is the part people miss.
Topping
A clean cut just above a node, removing the main growing tip entirely. The plant responds by pushing two colas from the node below the cut. Predictable, easy to do well on the first try.
FIMming
An intentionally imprecise cut through the newest growth, leaving some tissue behind. It tends to produce more than two new growth points, but the result is less consistent than a clean top.
The deadline that matters
Stop training by roughly week 27 at zone 5b. Training after that eats into the pre-flower window, and the plant may not have time to fully recover and even out its canopy before the flip.
What we do
We top twice: once early at four nodes, again about three weeks later on the resulting colas. It's given us a more even canopy than a single early top did in past seasons.