Author: Kira Turner | Master Gardener
The benefits of pruning have been debated for years now. Like everything there are benefits and draw backs to pruning, it's all about your personal preference and comfort level. One of the biggest benefits of pruning is increasing your yield, so for us, yes it is worth it!
What is pruning?
Pruning is the act of selectively removing branches and leaves from the plant. At the most basic level, this involves removing any dead, damaged, unproductive or unwanted branches. Doing this helps improve the plant's structure, promoting new healthy growth in the plant. This encourages new branch development, and also allows the plant to focus on growing faster, producing more chlorophyll and increasing overall yield.
It may sound easy but if pruning is not done properly it can also be detrimental to the health and development of the plant. Vigorous pruning can weaken the plant as a result of stress, this can cause a decrease in plant health and a smaller yield. It is important to know both when and what to prune, as doing it during the wrong phase of the growth cycle or taking off vital parts of the plant can cause irreversible damage. That is why pruning is not for everyone as it does come with risk, but, when properly educated the benefits of pruning can be endless!
When to prune
Pruning can begin when the plant is established, with several sets of leaves and internodes. This is usually 2 weeks into the growing phase when working with sativa dominant strains, and 3 weeks for indica dominant strains. The plant will continue to grow vigorously up until the 3rd week of the flowering phase. Therefore it is recommended to stop pruning after the second week of flower to ensure all of the plant's energy is put towards bud development. Throughout the course of the vegetative phase it is important to prune necrotic, chlorotic, and damaged material, as well as maintain the specific pruning style you wish to follow.
It is not recommended to prune heavily after the 2nd week of flowering. Heavy pruning can delay the onset of flowering, and potentially prevent flowering altogether. This can also be used as a strategy to delay the onset of flowering intentionally. Any pruning done during the flowering stage should be light, focusing on mainly fan leaves that are either blocking light from developing buds, disrupting air flow, or the leaves have become necrotic/chlorotic. It is important to continually monitor and remove any dying leaves as these are leaves that pests and disease typically thrive on.
Over time everyone develops their own pruning technique. Until you have come up with your own style keeping reading to learn more about the most popular techniques currently out there.
Defoliation is the most simple form of pruning. This is the practice of removing fan leaves. Typically the largest fan leaves, or leaves that are beginning to yellow and die. This is done to improve light exposure to lower bud sites on the plant and promote airflow through the canopy.
Topping is the practice of removing the main shoot(or apical bud) located on the main stem. The removal of the apical bud alters the plant's growth trajectory. Promoting more lateral growth, causing the plant to become bushier rather than tall and lanky. This technique is recommended as it helps maximize your plants access to sunlight. Where the apical shoot may have produced one large cola, topping the plant provides 4 colas with that same lighting. Topping promotes bigger buds as a result of better light access, and bushier more branched plants. Topping should be done very early so as not to slow the plants growth too much. If you plan to top your plant it should be done once your plant seems strong and ready. Make sure that you remove the latest shoot very carefully so as to not cause any damage. If done too late into the grow cycle the plant will not have enough time to grow wider and is not using its energy efficiently. Most importantly a plant can be topped multiple times, just make sure to allow recovery time between each pruning session.
Fimming is similar to topping but instead of removing the whole apical bud you are only removing it partially. When done properly this creates 4 main buds instead of 1. This creates a wider plant allowing for better light exposure, in turn increasing yield. This is a good technique to use for plants that tend to grow very tall. How exactly does fimming create main buds? After you cut ⅔ of the apical bud off the shoot grows into 2 new petioles. The middle of the shoot contains a new shoot, and new shoots will be formed in the axils. Removing ⅔ of the apical bud only removes the leaves while keeping the stems intact. These will become the main buds along with the shoots in the axils. Fimming can cause some damage to the leaves but that's totally normal and shouldn't have any real effect on the plant's health.This is also something that can be done multiple times through its growth cycle, just make sure to give the plant time to heal, and no later than the first week of flower.
To achieve this pruning technique you need to remove all the lower material on your plant to promote better bud development in the top of the canopy. This allows the plant to redirect its energy to the main cola sites. You can achieve this look by following two methods: Top down, or bottom up. Top down involves selecting a branch, counting out the last 3-4 nodes to have developed and removing everything else below it. While bottom up, you start at the bottom of the plan and work your way up. Making sure to remove any short main lateral branches, and leaves on the lateral branches. If the branch is being shaded and is not reaching the canopy it should be removed. Or remove any small buds that won’t fully develop. A general rule for this technique is to remove all leaf material from the bottom ⅓ of the plant. This style of pruning is typically recommended for screen of green (ScrOG) training.
Pruning tips & tricks
- Always use clean tools
- Prune during the early stages of growth for the best results and least amount of risk
- Always water your plant after pruning to help reduce shock and stimulate growth
- Make sure to take clean cuts when removing material from your plant as tearing or stripping the plant can increase risk for disease
- Do prune the young leaves or side shoots
- Make sure not to over prune as it can have negative effects on your yield!
- If no branches are growing out of a leaf’s basal stem, do not remove the leaf
- Do not remove all the leaves off of one branch or stem
Training your plant is the process of guiding your plant to grow a specific way without physically removing any material. This is done in cannabis to improve light distribution, improve airflow and induce low levels of stress to promote secondary metabolite production.
Super cropping involves crushing the stems' soft inner tissue.This is done by taking a branch between your forefinger and thumb, pinching and twisting at the same time until you feel the inside of the stem start to collapse under the pressure, slowly squeezing and bending the stem without snapping it. Breaking the inner wall of the plant's stem causes the plant to rebuild these tissues but stronger. During this rebuilding process the plant expands its cellulose network, which is why the stem grows back thicker. This allows for increased transportation of both water and nutrients throughout the plant. This also allows you to redirect the plant's growth, by bending the branches as you see fit, allowing more light to reach the lower buds. The branches will also become stronger because of the break and be able to hold more bud weight. Using this technique you can both shape your plant and improve plant health, and should typically be done during the 2nd or 3rd week of the vegetative phase.
Low-stress training (LST)
Every pruning and training method thus far has been an example of what is called high stress training (HST). There is the alternative option however of low stress training (LST). This is done by using string or rope like material to tie down sections of the plant. Typically the main shoot is tied down to promote growth in all the other shoots. The plant can be arranged in any way. The most common structure for LST is secure one tie on the base of the stem and second one to pull the plant down. As side branches grow they will need to be tied down to form an even canopy. This results in a plant that grows into a dense bush with an even canopy. For the best results using this training method make sure to take your time and remember to adjust your technique from strain to strain.
Sea of Green (SoG)
This method involves growing many smaller plants instead of a few large ones. The smaller plants tend to mature faster. This is a good method to use when you are limited on space and time but don't want to sacrifice your yield. Typically doing this the yield of an individual plant may be smaller but the total yield of the SoG will be larger. This method allows for a more even distribution of light among the main colas of the plants. Creating a dense canopy of buds allows you to make the most out of your space and lighting. It is recommended to pair the training method with pruning as well, lollipoping being a prime option, as the upper main colas will block out the light to the lower branches. Keeping these lower branches trimmed will also help maintain airflow throughout the canopy as well.
Screen of Green (SCroG)
This is a training method Is very similar to SoG but involves securing a screen above the canopy of plants, and using it to guide the plants through the trellis, and secure branches to the screen as it grows. Created to optimize lighting by bringing lower buds up to the top of the canopy. This is done to help with light distribution, which as a result improves yield. This helps your plant grow bushier and use its space more efficiently. This method should be used if you are trying to get the most bud development out of your plants and is recommended to be paired with pruning such as topping.
All in all there are many different techniques for pruning and training your plants, and people are coming up with new ones everyday. There isn't necessarily a right or wrong way to prune so keep testing out different methods to find the one that works best for you!