Topping, the removal of a plant’s main growth tip, is a technique used to encourage lateral branching and increase potential harvest volume. This process, known as High-Stress Training (HST), redirects the growth hormone auxin to the lower branches. This causes them to develop into multiple primary colas instead of a single main stalk. An autoflower is a cannabis plant that flowers automatically based on its age rather than relying on a change in the light cycle. Combining the high-stress nature of topping with the autoflower’s fixed, short timeline is a highly debated practice that carries significant risks.
Why Topping Poses a Risk to Autoflowers
Autoflowering plants differ from photoperiod plants because their vegetative growth phase is short and non-negotiable. This phase, when they build their structure, typically lasts only three to four weeks from germination before the plant begins flowering. Photoperiod plants can remain in vegetative growth indefinitely, allowing them ample time to recover from physical stress.
Topping inflicts a substantial wound, forcing the plant to allocate energy toward healing and hormonal re-regulation. This recovery process requires several days to a week. If recovery coincides with the plant’s programmed switch to flowering, it may enter its reproductive phase before reaching an adequate size. This premature flowering results in a stunted plant with reduced overall yield, defeating the training’s purpose.
Identifying the Narrow Window for High-Stress Training
Successful topping requires precise timing to ensure the autoflower has sufficient time to recover before flowering begins. The plant must be healthy and vigorous enough to handle the stress while still firmly within its vegetative phase. Growers should wait until the plant has developed at least three to four true nodes, which are the points on the stem where branches and leaves emerge.
This narrow window usually occurs between Day 14 and Day 21 following germination, depending on the strain’s speed. Topping too early can overwhelm a fragile seedling. Topping even a few days too late risks the plant entering its flowering stretch while still recovering. Missing this opportunity means the plant will not have enough vegetative time left to benefit from the technique.
Executing the Topping Cut Step-by-Step
The physical execution of the cut must be clean and precise to minimize trauma and reduce infection risk. Before making any cut, sterilize your tool, such as a razor blade or small scissors, using isopropyl alcohol. Sanitation prevents the introduction of pathogens into the open wound, which could stall growth.
Identify the apical meristem, which is the tiny, undeveloped growth tip at the top of the main stem. Make a single, clean horizontal cut just above the third or fourth fully developed node down from the top. The goal is to completely remove the apical tip while leaving the two small new growth shoots beneath it intact. These two shoots will receive the redirected growth hormones and develop into the plant’s new main colas.
Following the cut, monitor the plant closely for the next 48 to 72 hours for signs of recovery, such as lower branches beginning to grow more rapidly. Maintain optimal environmental conditions, especially stable temperature and humidity. Avoid any additional stressors during this period. A boost in nitrogen-rich nutrients can assist the plant’s initial regrowth phase.
Safer Methods for Canopy Management
Because of the risks associated with topping autoflowers, many successful growers utilize Low-Stress Training (LST) as the preferred method for canopy management. LST involves gently manipulating the plant’s growth without causing physical damage or open wounds, which eliminates the need for recovery time. This approach is better suited to the autoflower’s fixed, rapid life cycle.
LST is performed by carefully bending the main stem toward the horizontal and securing it with soft plant ties or wire. This technique breaks the plant’s natural apical dominance, allowing the lower side branches to grow upward and form multiple tops. Keeping the canopy level ensures that all potential bud sites receive equal light exposure, which increases overall yield without the risk of stunting the plant. Other low-stress methods include gently tucking large fan leaves out of the way to expose bud sites or using a Screen of Green (ScrOG) net to weave branches.