Topping is a high-stress training technique in cannabis cultivation that involves strategically removing the plant’s main growing tip to modify its natural growth pattern. This procedure manages plant height and increases the number of primary flower sites, directly enhancing the final yield. By manipulating the plant’s structure, growers encourage a bushy, dense canopy that makes better use of available light, especially indoors. The method intentionally stresses the plant to redirect energy from vertical growth into lateral development.
Understanding Apical Dominance
Cannabis plants naturally grow in a distinctive Christmas tree shape due to a biological phenomenon known as apical dominance. This vertical growth is controlled by the plant hormone auxin, which is primarily produced in the apical meristem, the uppermost growth tip of the main stem. Auxin travels downward through the plant’s vascular system, suppressing the development of lateral side branches lower down the stem. This concentration prevents lower nodes from becoming dominant growth points, ensuring the plant focuses energy on reaching maximum height.
Topping physically removes the main source of inhibitory auxin production, effectively breaking apical dominance. The absence of the dominant growth tip forces the plant to redistribute growth hormones and energy to the two side shoots immediately below the cut. These two lateral shoots quickly develop into new main stems, doubling the number of primary colas the plant will produce. This hormonal redirection shifts the plant’s growth from a single central stalk to a more horizontal, multi-branched structure, optimizing the canopy for light absorption.
Timing the Topping Procedure
The successful application of topping depends on performing the procedure during the plant’s vegetative growth phase. Topping should never be attempted while the plant is still a fragile seedling, as it lacks the necessary vigor and reserves for recovery. Growers should wait until the plant has developed a minimum of three to five healthy, true nodes before considering the cut. Waiting until the plant has four to six nodes ensures it has sufficient root structure and foliage to quickly recover from the high-stress training.
Topping the plant before it reaches the minimum size can severely stunt its development and lead to a slow recovery. Conversely, topping must be avoided entirely once the plant transitions into the flowering stage. During flowering, the plant focuses energy solely on flower production, and the stress of topping will halt bud development and significantly reduce the final yield. Ideally, the procedure is carried out early in the vegetative cycle, allowing the plant ample time to heal and establish its new branch structure before flowering begins.
Locating the Exact Cut Site
The physical location of the cut is the most important factor in a successful topping procedure. Standard practice involves counting nodes up from the base of the plant to identify the target location. Most growers aim to cut the main stem just above the third or fourth true node, leaving the two healthy branches at that node to become the new main stems. If the plant has six nodes, the cut is typically made above the fourth node, removing the fifth and sixth node growth tips.
Precision is necessary when making the cut to ensure the plant heals quickly and correctly. The cut should be made horizontally across the main stem using sharp, sterilized scissors or pruning shears. Sterilization with rubbing alcohol is important to prevent the introduction of pathogens, such as bacteria or fungi, into the fresh wound. The cut must be positioned slightly above the chosen node, leaving a small stub of stem tissue.
Cutting too close to the remaining node can damage the delicate new growth points. Cutting too high leaves a long, unnecessary stem segment prone to splitting or infection. The goal is a clean, swift cut that completely removes the apical meristem without crushing the remaining stem tissue. Immediately following the cut, the two lateral branches directly below the wound begin to receive redistributed growth hormones, accelerating their development into two distinct main colas.
Aftercare and Secondary Topping
Following the topping procedure, the plant requires a period of recovery to manage the induced stress. Growers should maintain stable, optimal environmental conditions, focusing on consistent light, temperature, and humidity to promote fast healing. This recovery phase typically lasts between five and ten days, during which the plant may temporarily slow its overall growth as it redirects energy to the wound site and the newly dominant side branches. Providing adequate nutrients supports the plant’s recovery efforts and the vigorous growth of the new shoots.
Once the plant has fully recovered and the two new main branches are actively growing, a secondary topping can be performed to further increase the number of colas. This involves treating each of the two new branches as a new main stem and topping them again above a lower node. Repeating the technique creates a dense, low-profile plant with four, eight, or even more main colas, a technique often used in methods like manifolding. Secondary topping should only occur after the plant shows robust new growth and has been allowed a full recovery period from the initial cut.