Why, when, and how to prune cannabis
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- Why do you prune cannabis?
- When do you prune cannabis?
- How do you prune cannabis?
Pruning is one of the most effective ways to manipulate and direct the growth of a cannabis plant. If you’re looking to limit the size of your plant, promote lateral branching, delay the onset of flowering, or increase yield, pruning checks all the boxes. It may feel counterintuitive to snip parts of your plant as it grows. But by pruning unproductive growth, you can redirect the plant’s energy and resources into developing quality flowers.
While pruning is reasonably straightforward, it’s also a skill that becomes refined and easier with practice. These pruning tips and tricks should help demystify the process.
Why do you prune cannabis?
Pruning refers to the process whereby small, specific sections of the plant are cut to encourage healthy growth. At its most fundamental level, pruning removes growth that is damaged, unproductive, or blocking sunlight from reaching budding flowers.
Pruning refers to the process whereby small, specific sections of the plant are cut to encourage healthy growth. Photo by: Gina Coleman/Weedmaps
The elimination of this growth enables the plant to focus its energy on nourishing and strengthening the remaining leaves, shoots, and buds. Successful pruning also promotes greater airflow and light exposure, fostering a more vibrant plant, and forming denser, more cannabinoid-rich buds.
While the principle of pruning sounds simple in theory, in practice it can be challenging. Excessive pruning can be detrimental to the health and development of the plant. It’s vital to always err on the side of caution when pruning cannabis plants. Vigorous pruning can weaken the plant through stress and subsequently reduce the yield. Pruning at the wrong time of the growing cycle or mistakenly pruning vital stems and shoots can inflict damage. For this reason, some new growers avoid pruning altogether, or others pare back their pruning to its most fundamental level, the removal of dead or yellowing leaves.
When do you prune cannabis?
Pruning is almost exclusively carried out during the vegetative growth stage before the cannabis plant is mature and ready to flower. The plant should be well-established in the vegetative phase, measuring approximately 12 inches (30 centimeters) tall with several sets of leaves before pruning is performed. If you’re looking to grow bushy, squat plants, keep the pruning to a minimum.
Judicious pruning during the early phase of vegetative growth will have little effect on flowering. Pruning more mature plants that are approaching the flowering stage is not recommended. At this later phase, heavy pruning can delay the onset of flowering, or prevent flowering altogether. In some cases, however, growers may wish to delay flowering intentionally, so strategic pruning can be a useful tool.
Pruning during flowering should be extremely light and limited. One example of appropriate pruning would be the removal of fan leaves that are shading healthy bud sites. The pruning of damaged, diseased, or dead plant tissue can be carried out throughout both the vegetative and flowering cycles. Yellow (chlorotic) or brown tissue allows invasive microorganisms and pests to thrive. Remove these leaves to make sure they don’t fall and become absorbed into the growing medium.
How do you prune cannabis?
The process of pruning requires only one tool: a sharpened, clean pair of pruning shears. Expert growers may have several pairs of shears of different sizes designed to prune different levels of growth.
It’s vital to sterilize the shears before pruning to prevent pathogens from hitching a ride directly to your plant. The place where the plant has been pruned can be vulnerable to diseases or infections until it heals. Sharp shears are critical to making clean, swift snips that can heal quickly and don’t cause undue damage to the plant.
Once your pruning shears are sanitized and sharpened, you’re ready to begin.
1. Topping or primary stalk pruning
According to Robert Connell Clarke, a cannabis cultivation expert, trimming the central stalk represents one of the most common pruning techniques. The tip of the central stalk is removed when the plant has reached its desired length. This removal encourages a bushy, laterally spreading plant, rather than a tall, stringy specimen.
Beneath the point where the central stalk has been removed, axial branches will form and grow two new limbs that ultimately spread outwards. This practice, also known as topping , is transformative because it alters the plant’s growth trajectory.
2. Removing big branches and leaves
Pruning the larger branches and leaves promotes instant airflow by creating space. It also allows light to reach more of the plant. Make the cuts as clean and as close to the stem as possible, and at a 45-degree angle. Once the larger branches have been pruned, it’s easier to shift attention to the smaller details.
3. Clearing space around the middle of the plant
Branches growing in the middle of the plant are not as resilient as those at the top. Spend some time pruning to create space around the middle.
Branches growing in the middle of the plant are not as resilient as those at the top. Photo by: Gina Coleman/Weedmaps
Very small limbs or branches grow around the lower parts of the plant, and tend to be atrophied. The removal of entire limbs allows the plant to channel nutrition into the upper stems, leaves, and buds. More air circulates in the lower reaches of the plant, minimizing the risk of mold when growing indoors. Most importantly, energy and growth hormones are directed upwards towards the buds most likely to thrive. This method is colloquially referred to as the lollipop technique or lollipopping. The plant takes on a lollipop appearance: bushy at the top with skinny and sparse foliage toward the bottom.
5. Pruning the leaves and bud sites
Remove any yellow, brown, or diseased-looking tissue. Also prune any leaves that have branches shooting from their base. Snip any buds heavily shaded by the canopy branches. The unfavorable location of these buds means they will not have access to adequate light and may have nutrient deficiencies.
6. Allowing time for recovery
Pruning inflicts stress on the plant, so allowing time for recovery is vital. Make sure you provide adequate water, light, and nourishment in the days after pruning to facilitate recovery from the shock. Within a week the growth of new shoots and leaves should be apparent. You can prune again once the plant has had the opportunity to recover. Always remember, however, that the excessive removal of shoots and leaves is a significant stressor and can inhibit growth and bud development.
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How to prune cannabis plants for maximum yields
Pruning is essential for improving the quality and yield of your cannabis plants. It’s an intimate practice between the gardener and the plant and allows you to closely look at your plants and check up on their health.
It might feel strange to intentionally cut off bits of your plant, but these parts won’t produce quality buds because they won’t receive a proper amount of light—they’ll get shaded out by the buds and foliage growing above.
Cutting off the branches will allow the plant to redirect its energy and resources to the quality buds that will receive plenty of light. You also want to prune off yellow or dead leaves on the plant—they have no use and will only waste the plant’s resources.
Pruning also creates open space in the middle of the plant, allowing air to flow through it more freely and letting light penetrate deeper, keeping the plant vibrant and healthy.
What to look for when pruning
Quality buds grow where the plant receives a lot of sunlight and airflow, particularly on the top of the plant. You’ll want to remove:
- Low-down branches that receive little sunlight
- Leaves that are dying off because of lack of light
- Bud sites that are low down and don’t receive a lot of light
In the early stages of growth, a plant is narrow enough that most of the foliage will receive plenty of sunlight. Start pruning your plants once they begin to take a bushy shape, and top them to promote this bushy growth.
As a plant grows and bushes out, it’ll start to take a shape and define the canopy. This will give you a sense of where the quality buds will grow so that you can start pruning away the unnecessary portions of the plant.
From this point until about 3-4 weeks into the flowering stage, you can actively prune your plants. Once well into the flowering phase, you want to cease pruning—it can cause the plant to start producing vegetative growth again, which will diminish the size and quality of your yield.
How to prune your cannabis plants
Grab a pair of pruning shears, usually some Chikamasas or Fiskars, for quick work on small branches and leaves. Keep an additional pair with more strength nearby to cut larger branches.
Keep your clippers/scissors sharp and make clean snips—this will keep the plant healthy and prevent infection and damage.
- Remove large branches first. This will allow you to clear out as much space as possible before you begin the more detailed work. Start with branches on the bottom of the plant. These won’t receive enough sunlight and will never become fully developed buds.
- Cut off branches that are growing up into the middle of the plant, underneath the canopy. These branches will get shaded out and also won’t develop full buds.
- Prune any small or dying branches or leaves.
In the days following a pruning, your plants should go through a burst of growth—the open space will allow extra light to get to the plant.
Pruning allows you to control the plant and direct where it puts its energy. Remember, pruning is a great opportunity to be present in your garden and to observe how your plants are doing. Take this time to also observe your plants and check their overall health, looking for pests, nutrient deficiencies, and soil issues.
Pruning your cannabis plants is essential for improving the yield and quality of your garden. Use our guide to learn how to prune your plants.