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A Guide To Cannabis Defoliation

Defoliation is a somewhat controversial topic among cannabis growers, some of whom swear by it, while others argue that the practice is detrimental to plant growth and health.

In a nutshell, defoliation refers to the removal of any excess cumbersome leaves to increase light penetration, improve airflow and ultimately boost yield in your marijuana plants. The idea is simple, increase direct light to buds as fewer leaves are in the way.

You’re giving the good stuff to the part of the plant that you’re ultimately going to harvest.

Why Defoliate Cannabis Plants

Some growers defoliate plants to get rid of any large fan leaves that may be preventing sunlight from reaching nodes and bud sites. Despite the controversy surrounding the whole topic, most growers agree that if you are going to defoliate, then you should only do so when cultivating plants in a grow room and not when growing outdoors.

This is because outdoor plants need all their foliage to help them resist the pressures and stresses of the wild. Big fan leaves act as solar panels, allowing plants to generate as much energy as possible from the sunlight they receive while also storing nutrients that can be directed to bud sites during the flowering stage. Outdoor plants are also susceptible to attack from pests, so the more leaves an individual possesses, the better its chance of survival if some of these get eaten.

cannabis defoliation guide

However, indoor plants live a more carefree existence, as their controlled grow space ensures they always receive optimal levels of light and nutrients, while an attack from pests is less likely. On the downside, life in a grow room means sitting beneath a fixed grow light rather than a moving sun, so the lower parts of a plant might not receive the exposure they need.

For indoor plants, too many leaves can become a burden, taking up space and shading out nodes. Many growers, therefore, choose to defoliate, knowing that their plants don’t need all their leaves and can survive losing a few.

When a certain percentage of this foliage is removed, cannabis plants can direct more of their energy and resources into creating bud and resin rather than supporting large fan leaves. Decluttering a plant in this way also allows for better light penetration, which facilitates the growth of larger buds. Finally, increased airflow ensures more efficient transpiration and reduces the risk of mould or other infections.

Collectively, these benefits can result in bigger yields and more potent weed, although it’s also very easy to go overboard with defoliation and stunt a plant’s growth. Knowing when to remove a leaf and when to leave it be is something of an art form that can only be mastered with experience.

Which Cannabis Plants to Defoliate

Because defoliation creates stress, growers should only consider applying this technique to robust and healthy cannabis plants. Those who appear frail or show signs of disease, nutrient deficiency, or other weaknesses should be left with all their leaves intact.

Unfortunately, there are no hard and fast rules governing which plants are suitable candidates for defoliation and which are not, so a degree of experimentation is always necessary to determine how well a plant can withstand the shock. However, it makes sense to assume that cultivars with hardy genetics are likely to fare better than those with a reputation for being fussy and high-maintenance.

It’s also worth bearing in mind that Sativa cannabis seeds tend to give rise to plants with thin, finger-like leaves, while Indicas are often much bushier. This extra foliage makes the latter better suited for defoliation, although this rule is not set in stone once again.

The best way for growers to determine which cannabis plants to defoliate is to cautiously give it a try by snipping a couple of leaves. If plant growth is stunted, then you’ve probably removed too much greenery. Excessive defoliation can also disrupt transpiration, resulting in a build-up of nutrients in the roots and causing nutrient lockout.

cannabis defoliation guide

Defoliation can improve light penetration and airflow.

How to Defoliate Cannabis Plants

Cannabis defoliation is all about removing material that is doing more harm than good, so it’s important to be selective about which leaves to snip. Those at the top of the plant should be left alone, as they will likely receive the optimal amount of light.

Focus on the bottom of the plant, removing large fan leaves that are shading out key nodes and bud sites and inward-growing leaves that are cluttering up the space around the main stem. Old, yellow leaves that are no longer carrying out photosynthesis or contributing to the health of a plant can also be cut.

Many growers choose to defoliate around a week or so during the vegetative stage before switching to a 12/12 photoperiod. This allows the plant sufficient time to recover from the shock before entering the flowering stage. Most people don’t bother defoliating autoflower cultivars, as these usually stay small and have a very short veg phase.

Using sharp, clean scissors to minimise the risk of infection, a grower can begin by removing just a few leaves and cutting close to the stem. When working with a plant that has previously stood up well to defoliation, it’s acceptable to proceed with greater confidence and remove up to about 20 percent of the leaves below the third or fourth node from the top.

Some growers then perform a second defoliation about three weeks after the start of the flowering stage. At this point, many leaves will naturally drop off as the plant no longer needs them to grow veg, although it’s still important to err on the side of caution and only remove those that are clearly hindering bud development.

cannabis defoliation guide

Cannabis Defoliation vs Pruning

It’s worth pointing out that defoliation is not the same thing as pruning, although many cannabis growers like to use both of these techniques on their plants. The fundamental difference is that defoliation techniques only involve the removal of leaves, while pruning entails the cutting of stems and nodes to restructure the shape of a plant.

There are many ways to prune a cannabis plant, each of which will result in a particular arrangement of stems and colas. Lollipopping, for instance, refers to the removal of everything except the primary end bud on each branch, giving a skinny stem with a bushy head.

Unsurprisingly, pruning is considered a high-stress training technique, while defoliation is a form of low-stress training (LST). Experienced growers tend to mix and match their favourite methods, although it takes a lot of practice to find the right balance, which is why beginners are advised to keep things as simple as possible when starting out with their weed plants.

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

This post is also available in: French

Ben Taub