Topping, a high-stress training technique, involves removing the main growing tip of a cannabis plant to manipulate its natural shape and increase its potential yield. This method encourages a flatter, bushier structure instead of the typical Christmas tree shape. By altering the plant’s architecture, growers aim to maximize the efficiency of indoor lighting and promote the development of multiple large flower clusters, known as colas. Correct timing in applying this technique is paramount, as performing the cut too early or too late can negatively impact the plant’s recovery and the final harvest size.
The Purpose of Topping
The natural growth pattern of cannabis is dictated by a biological mechanism called apical dominance. This phenomenon is driven by the plant hormone auxin, which is produced in the highest concentration at the main growing tip, or apical meristem. High levels of auxin are transported downward, effectively suppressing the development and growth of the lateral side branches below.
Removing the apical tip through topping immediately disrupts this flow of auxin, eliminating the hormonal signal that inhibits lateral growth. This action causes the plant to redistribute its growth energy and resources to the dormant side shoots. Consequently, the lower branches are released from their suppression and accelerate their growth, transforming the plant into a wider, more uniform canopy with multiple dominant shoots. This structural change allows for a more even distribution of light penetration across the entire plant surface, leading directly to higher yields by creating more sites for large colas to form.
Determining the Initial Timing
The first topping cut depends entirely on the plant’s maturity and overall health. Topping should only be attempted during the vegetative growth phase when the plant is robust and actively growing. Attempting this high-stress technique on a seedling or a plant that is already struggling can cause severe stunting or even death, as the plant lacks the necessary energy reserves to recover.
A well-established guideline is to wait until the cannabis plant has developed at least four to six fully formed nodes, which are the points on the stem where leaves and branches emerge. This node count ensures the root system is sufficiently established and the plant has enough lower branching to continue photosynthesizing and recovering quickly. Cutting above the fourth to sixth node allows the remaining part of the plant to utilize existing resources effectively and redirect them into the two new growth tips that will emerge just below the cut. Topping too early, before this developmental stage, risks a prolonged recovery period that can delay the growth cycle significantly.
Subsequent Topping and Stress Management
For growers aiming to maximize the number of main colas, subsequent topping cuts can be performed on the new growth tips that emerge. The timing for these follow-up cuts is governed by the plant’s recovery rate from the previous stress event. A minimum recovery period of one to two weeks is generally required between toppings, allowing the plant to stabilize and regain its vigorous growth before another cut is made.
Observing the plant’s growth vigor is the most reliable indicator for readiness, as the two new main stems should be actively growing and have developed a few new nodes themselves. This repeated topping process must be halted well before the transition to the flowering stage to prevent yield loss. It is generally advised to stop all high-stress training, including topping, at least two to three weeks prior to switching the light cycle to bloom. This necessary buffer period ensures the plant has sufficient time to heal, strengthen the newly formed branches, and focus its energy entirely on flower production rather than repairing damage when the flowering stretch begins.
Executing the Topping Cut and Aftercare
The physical act of topping requires precision to minimize the risk of infection or unnecessary damage to the plant. Begin by sterilizing the cutting tool, such as pruning shears or a razor blade, with rubbing alcohol to prevent introducing pathogens into the open wound. The cut itself should be made cleanly and decisively across the main stem, just above the node chosen for removal.
An ideal location for the cut is slightly above the junction of the stem and the leaves of the next lowest node. This placement encourages the two side shoots at that node to become the new main colas while leaving a small stub that will quickly dry out and seal. Immediately following the cut, the plant will enter a brief period of shock, which might manifest as slight drooping of the leaves. Maintaining optimal environmental conditions, including stable temperature, proper humidity, and consistent light, is important to support the plant’s rapid recovery and the development of the new growth.