Growing cannabis can be done in many ways, every grower has their own techniques and tricks to increase their yields. One subject that is always subject to debate is defoliation: the removal of leaves. Do you defoliate your cannabis plant, and if so when and how much?
Pruning is any form of removing plant material to have a plant grow a certain way. Defoliating is a form of pruning that literally means removing fan leaves from a plant. Pruning has been used for thousands of years on many agricultural crops to increase yields and reduce the amount of smaller, unusable fruits. Most growers agree that this technique also works very well for growing cannabis and will incorporate defoliation into their grow cycles.
Defoliation can be extremely helpful in terms of airflow and light use. Removing excess fan leaves and branches allows more air to pass through the lower parts of a cannabis plant and will reduce the threat of mold or bud rot.
Defoliation is often combined with removing branches, these are both forms of pruning but target different parts of the plant. Pruning helps to make sure lower parts of the plant receive enough light, which stimulates bud formation and ripening. There is also a limited amount of growth hormones that is distributed throughout a cannabis plant. The most well known groups of plant hormones include auxins, gibberellins and cytokines. These so called “growth regulators” control growth rate, size and development. Smaller, lower bud sites are often removed completely to focus all of these growth regulators towards the main colas. Besides increasing your yield, pruning your cannabis plants like this makes your harvest more uniform and much easier to trim. Techniques like “Lollipopping” (removing all lower growth from a cannabis plant) have become common in the cannabis community.
While most growers agree that defoliation and pruning benefit their cannabis plants, it is virtually impossible to find two people that do this the exact same way. Every grower will have a different opinion on when you should remove leaves and how many.
Growers use different techniques and tools for pruning and defoliating cannabis plants. Some remove everything by hand, bending and pinching as they go along. Others like to work a bit cleaner and use scissors or even razor blades that are cleaned with 96% ethanol before and after use. In our opinion the technique is not nearly as important as the timing and the amount of plant material you remove. We like to defoliate by hand, as leaves generally snap off easily when bent at the base. Make sure you have clean hands if you decide to do this! Other pruning and especially topping (and FIMming!) is usually easier and more accurate using scissors.
Defoliating a cannabis plant will have a slightly different effect in different stages of the cannabis life cycle. As with other pruning techniques, pruning and defoliating during vegetative growth is quite harmless. Even if a cannabis plant becomes stunted in veg, it will bounce back quickly and won’t be noticeable later on during flowering. Defoliating right before or at the start of flowering is common practice in a lot of gardens.
Defoliation during flowering is a bit more controversial, as stunting a cannabis plant anywhere in this 8-12 week window will probably affect the yield. There are are however many growers who like to defoliate during flowering with great success. They either gradually remove leaves to avoid any plant stress, or rely on their plants getting over their shock quickly. Our general rule is that defoliation and pruning is fine until about the third or fourth week of flowering. After a cannabis plant finishes stretching, we like to avoid any further defoliation. Gradual defoliation or stripping a cannabis plant in one session is both fine in our opinion, though we prefer the latter for practical reasons.
Defoliating is a constant trade-off between production capacity and efficiency, it can be difficult to find a balance between the two. Defoliating can have all the benefits that we described earlier, but we also know that photosynthesis occurs in the leaves.
Growers that take a very light approach to defoliation argue that cannabis plants usually know what’s best for them. In their opinion defoliation is something that should only be done when necessary, like when airflow starts becoming a problem. Rather than picking off yellowing leaves, these growers will allow their plant to use every last bit of energy from them.
On the opposite end of the spectrum, you have growers that strip plants of nearly all their leaves and lower branches. These growers are convinced that a cannabis plant does not need many leaves once it starts flowering. They argue that a cannabis plant still has to dedicate a lot of energy to keeping their leaves healthy, energy that could otherwise be used for producing buds.
Defoliation is something most growers get into gradually, experimenting a bit more with each grow. Defoliation can seem very dangerous, as you don’t want to stunt your plant. In the following section we’ll discuss a video by a grower with a clear opinion on defoliation to show you what’s possible.
The author of this video, HIGROWMEDICINAL, definitely likes to defoliate cannabis plants and makes a convincing argument that this increases yields. Let’s take a closer look at how he uses defoliation and his reasoning behind it!
The first thing you’ll notice is that the scale of this grow is huge: hundreds of cannabis plants and dozens of lights. Rather than scrogging, the grower has chosen to use tomato cages to support the plants, which allows them to be moved individually. The plants are all grown hydroponically, which increases vegetative growth in most strains. Keep this in mind before comparing this video to a soil grow!
HIGROWMEDICINAL starts by explaining that he is a bit of an “extremist” when it comes to defoliation. He removes virtually all fan leaves with a stem (= petiole) longer than a few centimetres. Many growers like to gradually defoliate their cannabis plants to avoid shocking the plant, but the author of this video disagrees. In his opinion it is better to get it all done at once to reduce the chances of shocking your cannabis plant later.
The best time to defoliate in this style would be after week 3 of flowering for 8 week strains, and week 4 for 9-12 week strains. Week 5 would be late, but is possible with many strains. The plants in the video are being stripped a day early at day 20.
This style of defoliation involves removing most of the large fan leaves except for a few at the very top of a cola. During this process, you’ll also want to remove smaller buds from the bottom of the cannabis plant. Sativa dominant strains will be easier to defoliate as they are generally less leafy. Over the course of this sped-up video, three plants are stripped in 20 minutes of real time. The author says he typically works with 12-20 light gardens, and usually spends about three days per grow to defoliate every plant by himself.
After explaining exactly how he defoliates, he explains that a cannabis plant doesn’t need big fan leaves after the third week of flowering in his opinion. While this is definitely a controversial statement in the growing community, this guy does seem to know what he’s doing! We’re impressed at least and “won’t knock it ‘till we try it”.
HIGROWMEDICINAL goes on to explain that defoliating makes growing cannabis easier and more productive. It also makes his harvest free of small, larfy buds. He likes to think of his defoliating process as sort of a pre-harvest, making the final harvest much easier.
Most growers won’t take defoliation as far as the grower in the video, but some interesting points are made. Given the amount of leaves removed, this video should be reassuring for growers that are afraid they will damage their cannabis plants beyond repair. The grower in the video also gives a nuanced view on stunting plants during flowering, stating that “they’ll be fine in a day or two”.
We generally like to defoliate more than the average grower, but this also depends on the medium. When growing cannabis indoors, we like to grow on coconut coir, mapito or in deep water culture. These hydroponic methods usually cause a cannabis plant to explode with growth during the vegetative stage and early flowering, making defoliation almost mandatory. In hydroponic indoor grows, we like to defoliate and prune our cannabis plants to the same extent as HIGROWMEDICINAL does in the video.
For outdoor grows we like to use soil, this gives us more stability but less explosive vegetative growth. Because of this, our outdoor pruning and defoliation routine is also less extreme than what we use for indoor hydroponic cannabis plants. Because the sun can penetrate deeper than grow lights, more lower branches can stay on the plant and only the smallest branches are removed. Fan leaves are removed if they are directly on top of a flowering site, or if they become damaged. Removal of fan leaves in outdoor grows is also very weather dependant, leading us to remove more leaves in weather conditions that promote powdery mildew and budrot.
There is definitely a huge difference in size between the grow in this video and the small home grows most people are running. The huge amount of plants in the grow room makes it clear that we’re dealing with a professional that might have different goals than a hobby grower.
The author states that he runs the whole grow by himself, this basically forces him to use as many techniques to reduce trimming time at harvest as possible. Growing cannabis at this scale makes using your time efficiently more important than in a smaller setup. The larfy, waste-of-time buds this grower describes might still be small treasures to people that grow a single cannabis plant per run.
As mentioned before, the fact that the whole grow runs on HID lighting means that this style of defoliation might not necessarily be a good idea for outdoor plants. Sunlight can penetrate deeper into the canopy than HID lighting, this makes shading by fan leaves less of an issue when growing cannabis outdoors.
Finally the medium matters quite a lot when it comes to vegetative growth. A cannabis plant will generally perform better during veg when grown hydroponically than in soil. There are even large differences between different kinds of hydroponics. A cannabis plant will grow faster in coconut coir than in soil, but in more or less the same way. Techniques like deep water culture however will make your cannabis plants explode during veg and will end up forcing you to defoliate them. A good rule of thumb is that the more accessible nutrients are, the more foliage a plant will produce.
By presenting a few different approaches to defoliation, we hope to have given you an impression of how many techniques exist. We’d like to encourage you to try it on your plants and start developing your own unique style. In any case, we’ve shown you that a cannabis plant can take a lot more than you might think!