Pruning Cannabis Plants — Why, How, and When | Grove Bags (2024)

Those who grow cannabis know there is a litany of reasons to strategically prune marijuana fan leaves; such as balancing light exposure, controlling the growth, preventing disease and mold, increasing the number of flowers, and encouraging strong structural development. Ultimately, pruning cannabis can help cannabis growers increase the bud quality and yield from their harvest.

Trimming fan leaves is a necessary and delicate part of cultivation. While experienced growers are adept at recognizing and removing diseased leaves, they are also pruning marijuana plants’ branches and leaves in a particular manner to achieve a specific result.

How do cannabis fan leaves work?

Fan leaves contain low levels of THC, which makes them useful for herbal teas and extracts, but not for smoking. More significantly, the fan leaf helps the plant develop the best buds possible.

Much like most of the plant world, cannabis fan leaves are a key component of the photosynthesis process. This iconic fingered leaf is composed of the petiole, apex, ventral, and dorsal surface. The petiole is the short stem that connects the leaf to the branch and the apex refers to the tips of the leaves. The ventral surface is the top side of the leaf, which absorbs light, and the dorsal surface is the underside of the leaf, which stores small amounts of water.

The vast majority of photosynthesis occurs in the leaves of a plant, which are exposed to the most light. All the leaves of a cannabis plant are necessary for healthy growth, but the fan leaves are the largest and take in the most light, but they also cast the largest shadow when fully developed.

Photosynthesis refers to the process through which plants use sunlight to synthesize nutrients from carbon dioxide and water. There is both a light-dependent and light-independent portion of this process. Sunlight, water, and carbon dioxide work together to produce oxygen and energy in the form of sugar. Each fan leaf is equipped with pores called stomata, which allow the plant to breathe. After the plant takes in carbon dioxide for the production of nutrients it releases oxygen through the stomata.

Maintaining and managing fan leaves appropriately is essential to a high-quality harvest. Big green fan leaves are a sign of appropriate chlorophyll levels in a cannabis plant. Chlorophyll is the substance in plants that absorbs light to spur growth. However, fan leaves that grow too large or dense can sometimes block valuable light penetration and airflow to the bottom of the plant—which is why we start pruning.

When to begin pruning cannabis plants

The need to prune fan leaves often changes depending on the conditions under which a cannabis crop is grown. It is imperative for growers to obtain a thorough understanding of defoliation so they can successfully care for each unique crop.

When pruning cannabis plants, over-stressing the plant can be avoided by pruning and defoliating a little at a time. Trim off the highest priority leaves and bud sites first. Then wait a week or two before pruning your plants again. Do this three to four times if desired, but you’ll likely want to stop pruning after five or six weeks of flower to avoid over-stressing the plants and causing them to herm.

During the vegetative stage, when the seedlings are growing quickly, pruning is often required. After a few leaves have emerged from the stalk, around the second week of vegetation, the plant is ready for its first pruning. This phase can produce a lot of growth in a short amount of time, which can limit a cannabis plant’s access to light. Strategically removing large fan leaves from the plant allows ample light to reach each bud site on the stalk. When the plant is exposed to more light, it will more quickly enter the flowering phase, which is the final stage of growth. It may feel counterintuitive to be pruning cannabis during the vegetative stage, but the flowering process is often compromised if the grower fails to prune beforehand.

When a plant has entered the flowering stage, it will likely require another round of defoliation. If a part of the plant is not receiving the light it needs, bud sites will not develop as effectively. When plants begin to bud, pruning becomes more of a maintenance task. It is important to remove damaged or dying leaves from the plant so the healthy leaves can do their job. Many cultivators choose to trim the leaves from the plants for only the first two weeks of the flowering stage to allow for appropriate bud maturation.

Because the conditions of an outdoor grow are unpredictable, with uncontrolled airflow and sunlight, pruning the lower branches of the plant can make a world of difference in the health of a crop. Outdoor plants rely on the natural breeze and the different light angles provided by the sun as it moves across the sky each day. It is important for growers to optimize a crop’s exposure to the elements without stripping it of its ability to photosynthesize.

Just like any plant, singular leaves can die or become ill during the growth process, and it is important to remove those leaves and allow the plant to focus its limited energy on healthy growth. This is especially pertinent for outdoor growing, but the same conditions can occasionally occur in indoor crops. If leaves are wilting or turning yellow and brown, their viability is declining. These leaves must be removed as soon as possible because damaged leaves suck energy from other parts of the plant, diverting nutrients from the bud sites. Applying the right pruning technique at the first sign of a pest or sickness can save cultivators from massive crop loss.

How to prune your fan leaves

Pruning cannabis plants requires simple tools and observant cultivators. Sharp scissors or a designated pair of pruning shears work best for removing fan leaves or topping cannabis plants. When snipping off lower interior leaves before harvest time, a fine scissor or pruning snips are preferred by many seasoned growers.

Whether you are removing fan leaves during the vegetative or flowering stages, it is important not to remove too many leaves at one time. Defoliating is a sensitive process, and if it is not done properly, the removal of the leaves can shock the plant, trigger early flowering, and produce a less impressive yield. Most cultivators prioritize the removal of yellowing or wilting leaves first to optimize the health of a plant.

The process should be done in stages and each big removal session should be conducted at least one week apart. Prior to the flowering stage, growers often remove around half of a plant’s fan leaves to encourage bud production. Right before it is time to harvest the buds, you can remove most of the fan leaves from the plant. However, it is important to allow a few days for the plant to recover before harvesting.

There are three types of popular trimming techniques in cannabis cultivation: topping, fimming, and lollipop. Topping removes a growing point by pruning directly above a node. Fimming is carried out to increase yield by cutting through the small leaves at a growing point, leaving about 30 percent of the growing point intact. And lollipop refers to the shape of the plant after applying the lollipop technique, with all the growth focused at the top of the plant with bare stalks at the bottom.