Topping a plant is a high-stress training (HST) technique that involves removing the main growing tip, or apical meristem, of the stem. This deliberate pruning alters the plant’s natural growth structure from a single, Christmas-tree shape into a wider, bushier canopy. The primary goal is to increase the plant’s overall yield by creating multiple primary growth sites that receive more light exposure.
The Biological Purpose of Topping
The effectiveness of topping is rooted in a natural plant phenomenon known as apical dominance. In an untopped plant, the main shoot produces a growth hormone called auxin, which travels downward through the stem. This high concentration of auxin near the top actively suppresses the development of lateral buds, forcing the plant to prioritize vertical growth.
Removing the apical meristem immediately eliminates the primary source of this growth-inhibiting auxin. The sudden drop in the hormone’s concentration releases the lateral buds from suppression, allowing them to activate and grow into new side branches. The plant redirects its energy and resources into these side shoots, effectively turning the two branches immediately below the cut into new main stems. This hormonal shift transforms a tall, single-cola plant into a broader structure with multiple main stems, maximizing the potential harvest.
Proper Timing for Initial Topping
The timing of the initial topping is important because the plant must be mature and robust enough to handle the stress of the procedure. Topping should only be performed during the plant’s vegetative stage, when it is focused on structural growth rather than flower production. A plant that is topped too early will often struggle to recover, leading to stunted growth.
The most reliable metric for determining readiness is the plant’s node count. Most growers recommend waiting until the plant has developed at least four to five fully formed nodes before making the first cut. At this stage, the plant has established a strong root system and enough energy reserves to recover quickly. Cutting above the fourth or fifth node ensures the remaining plant has enough lower branches to take over as the new main stems.
Factors Limiting the Number of Toppings
The question of how many times a plant can be topped is not governed by a fixed number but by three main constraints: recovery time, cumulative stress, and the finite vegetative period. Practical gardening cycles impose strict limits, meaning each subsequent topping must occur only after the plant has fully recovered from the previous stress event. Recovery typically takes between one and two weeks. During this time, the plant must heal the wound and establish the new lateral branches as the dominant growth tips. Attempting to top the plant again too soon will compound the stress, potentially leading to stunted growth or other signs of distress.
The absolute limit is imposed by the transition to the reproductive stage. Topping must be stopped completely at least one to two weeks before the plant is switched into its flowering cycle. The plant needs all its energy to focus on developing buds or flowers, and the stress of a late topping can severely disrupt this process, potentially reducing the final yield. For this reason, most common gardening cycles allow for a practical range of two to four total toppings. This range maximizes the number of new main stems while still allowing ample recovery time before flowering begins.