What Is Topping?
Topping is a way to increase the number of head (bud) sites on an individual plant. It can be considered a form of stress training, specifically, a high-stress training method, that is related to pruning in method. If un-topped, the plant will grow into a Christmas tree shape with one large cola at the top. By implementing topping techniques, the grower can sculpt the plant into a hedge shape with multiple head sites. This technique is very important with large plants. Often, the amount of times a plant is topped depends on the pot size and plant spacing within the canopy. Plants in small pots with a tight plant spacing may only need one topping.
Topping is performed by pinching or cutting off the terminal bud site at the tip of the plant. When you remove this site it forces growth hormones to circulate to lower areas of the plant. When a plant has three to five nodes it is developed enough that you can top it. That is about thirty days into the vegetative growth stage. You should not top plants when they are seedlings, and also should not perform topping once plants have entered the floral growth stage. Topping typically results in two new growth sites, but if you want to risk using a high-stress training method the FIM technique can yield four new growth sites. Fimming involves pinching or cutting off about 75% of the tip of a plant. When done correctly it can have great results, but if not performed correctly it can cause too much stress to the plant and kill it.