What are Topping and Fimming?
Naturally, cannabis plants usually grow tall and thin with one main cola at the top and many smaller branches below. To optimize space and increase yields with multiple large colas, cannabis growers can utilize high-stress training techniques known as topping and fimming. These methods involve periodically cutting off the top growth of the cannabis plant during the vegetative stage to redirect nutrients and energy for growth towards the lower, secondary branches. More light is also now able to penetrate lower branches and more colas are able to develop, resulting in the plants growing much bushier. Instead of the plant focusing all its resources on producing the one main cola, it now distributes its energy among its shoots to produce many, large buds. This not only will result in a much better yield, it also helps with growers constricted on vertical space since the cannabis plant will now grow much shorter and bushier. Where the two techniques differ is topping removes the entire tip, while fimming removes the majority of the tip but still leaves some of the foliage attached.
Advantages & Disadvantages
When a grower tops the entire tip of the plant, this allows the two nodes below to each develop into colas, doubling the number of colas in a symmetrical way. However, since you are cutting the central cola off, this can be stressful and delay plant growth while it is recovering and adjusting. Since fimming does not involve removing below the entire stem, and rather just cutting towards the base of it, it is less stressful for the plant to recover from. It also can spur the growth of multiple new colas, rather than just two. However, the growth of these new colas is less predictable, making the shape of your plant less uniform and may require extra supporting structures compared to using the topping technique.
Tips For Success
Topping and fimming are high-stress techniques, so it is important you only start doing so once the plants are developed enough to handle the stress of removing the main cola. For topping, the plant should have already developed substantial roots and have at least five to seven nodes. Top above the fifth node and soon two new ones will start to grow. After a couple of weeks, once those new nodes are large enough, you can top these new ones as well to double the number of colas once again. Remember the plants need time to recover after topping, so make sure you do not repeat the process too quickly before the plant is ready to handle the stress. When fimming, you can start the process once only three or four nodes have developed. Even though this technique is less stressful, you still want to wait a couple of weeks before fimming again to ensure you are not causing more stress and stunting the plant’s new growth. For both techniques, the increased production of heavy colas can make the plant more top-heavy, requiring additional support such as bamboo stakes. Once your plants have reached the flowering stage, do not continue either of these techniques. At this point, all colas are developed and you want the plant to focus all nutrients and energy on developing them to their maximum potential.