One aspect of good marijuana cultivation that is often overlooked is the ability to prune cannabis plants effectively. Pruning not only helps to shape and train the plant’s development, which can be absolutely essential in small spaces or when growing in a “sea of green” (SOG) or “screen of green” (ScrOG) setup; if done correctly, it can also serve as a way to increase potency and yields.
At the most basic level, pruning is simply the removal of parts of the plant, such as individual leaves, branches or even small buds. As a rule of thumb, it’s always a good idea to remove any dead or dying parts from a plant. But pruning can also help the plant to develop and function more efficiently. Sometimes this entails the removal of living or seemingly vibrant and healthy parts of the plant as well. The goal here is to direct energy and growth to the areas of the plant that you want to see most developed. The “conservation of energy” principle states that all energy that hasn’t been wasted can be redirected. In the case of cannabis, the top third of the plant is where the largest flowers develop, and redirecting energy there via pruning helps to increase resin production and, ultimately, yields.
Thus, trimming off leaves can be an essential part of a good pruning program. While larger, dark-green leaves look pretty and healthy on your plants, it’s important to realize that halfway through a leaf’s life, it has reached its photosynthetic peak. This means that photosynthesis gradually begins to decline in the leaf, and it creates less sugar (glucose) for the plant’s nourishment with each passing day. Eventually, the leaf will consume more energy than it produces. For this reason, many growers tend to take off the larger leaves in order to redirect that energy to the newer, younger leaves and buds ￼￼￼￼￼￼￼￼￼developing near the top of the plant. For best results, trim the fan leaves from the plant in a prudent and methodical fashion. When removing foliage, look for leaves that have reached their full size. These can include large leaves with a lighter color and purplish leaf stems. Additionally, shaded leaves are good candidates for removal, as they will not produce at maximum efficiency. This is why many expert growers trim off nearly the entire bottom third of their plants — especially in compact gardens where the plants are right on top of each other.
As mentioned earlier, it’s important to exercise restraint when pruning plants. Never remove leaves that are still developing, and be careful not to remove too many leaves at one time. Depending on the size of your plant, removing as few as two or three leaves per day may be the limit for what it can handle. Larger plants, especially those grown outdoors, can withstand more vigorous pruning, and they will likely require it if they are bushy and tree-like in size.