Topping is a cultivation technique where the grower physically removes the newest growth tip from the main stem of the cannabis plant. This process is a form of high-stress training (HST) intended to modify the plant’s structure to maximize yield potential. The goal is to force the plant to grow outwards rather than upwards, creating a flatter, bushier canopy. By performing this structural modification, the grower increases the number of primary bud sites, which ultimately leads to a more abundant and evenly developed harvest.
The Purpose of Apical Dominance Manipulation
The plant naturally grows with a single dominant central stem, a phenomenon known as apical dominance. This results in the classic “Christmas tree” shape, featuring one large central flower cluster, or cola, and smaller side branches. Apical dominance is regulated by auxins, hormones produced in the apical meristem (the tip of the main stem).
These auxins flow downward, suppressing the development of lower lateral branches. When the main growing tip is removed, the source of this growth-inhibiting hormone is eliminated. The plant’s energy and auxins are redistributed to the nearest lateral growth tips, forcing those side shoots to develop into two new main stems and creating a multi-cola structure.
Timing and Preparation for Topping
Timing the cut correctly is crucial because topping is a high-stress procedure the plant must be healthy enough to withstand. The ideal time to perform the first topping is during the vegetative growth stage, when the plant is actively growing and has established a robust root system. Growers should wait until the plant has developed at least four to six true nodes (the points on the stem where leaves and branches emerge). Attempting to top a seedling with fewer than four nodes can significantly stunt its growth or cause permanent damage.
Before making the cut, prepare the tools to prevent introducing pathogens into the wound. Sterilize a sharp instrument, such as pruning scissors or a razor blade, using rubbing alcohol to ensure a clean, infection-free cut.
Step-by-Step Guide to Executing the Topping Cut
The topping procedure involves a quick, precise cut to remove the newest growth tip while leaving the two lateral nodes directly below it intact. Locate the most recent growth at the top of the main stem. The cut must be made just above the node you wish to keep, as this node will become the new main branches. Aim to cut the main stem cleanly between the fourth and sixth node, removing everything above that point.
The cut should be made just a few millimeters above the two tiny, undeveloped auxiliary buds that emerge from the main stem at the chosen node. Making a clean, decisive snip is important to minimize the open wound and reduce the time the plant needs to heal. The resulting wound will scab over, allowing the two auxiliary buds below the cut to begin growing as the new dominant stems.
Post-Topping Care and Expected Growth
Immediately following the topping cut, the plant enters a recovery phase, and vertical growth will slow down for several days. This temporary slowdown allows the plant to heal the wound and redirect energy to the two new growth tips. Monitor the plant for signs of stress or infection, such as wilting or discoloration at the wound. Under favorable conditions, the plant typically bounces back quickly.
The two lateral shoots that were previously dormant will become the new main stems, growing outward in a “V” shape. This new structural development is usually noticeable within five to seven days as the new branches thicken. Once these new stems have developed two or three nodes of their own, the grower can perform a secondary topping to double the number of main colas, further increasing the potential number of flower sites.