How to Defoliate and Prune Cannabis Plants for Maximum Yield

Updated on Aug 04, 2022

Man Standing beside a large outdoor cannabis plant while defoliating the extra leaves during the flowering stage

" First off, why do people defoliate & prune their cannabis plants?"


" Simple! Defoliation & pruning have some key benefits."  


1. It increases overall yield

2. It increases cannabinoids

3. It produces bigger buds

Icon of a cannabis flower black and white

4. It decreases pest pressure


Did you know that...


Nearly 100% of legal commercial cannabis growers defoliate and prune their cannabis plants? If they didn’t, they would run into multiple problems such as pest pressure and low-quality bud.


If nearly 100% of commercial growers defoliate and prune, why shouldn’t you?


No more waiting. Let’s get right into it!


"The BudTrainer"

Defoliation & Pruning

Method

Tools needed:

  • Garden scissors (optional)
  • Rubber gloves (optional)

Difficulty Level:

Beginner



First off, what is the difference between defoliating and pruning?


Defoliating


The act of removing or cutting the leaves off a plant. “Folia” = leaves in latin.

Pruning


The act of removing or cutting the branches off a plant.

Diagram showing the difference between pruning and defoliating cannabis plants

Defoliating = cutting leaves || Pruning = cutting branches


WARNING!



Do NOT defoliate or prune when:



  • Before the 5th node appears: young seedlings are fragile and they need as much nurture and care as possible. This is why it is important to leave your cannabis seedlings untouched until they have at least 5 nodes.

  • 3 to 5 days before flowering: always leave 3 to 5 days between defoliating/pruning and switching your plant to flower. This way it has a few days to recover from the stress caused by cutting its parts.

  • Between day 1 and 21 of flower: during the first 3 weeks of flower your marijuana plant is going through an aggressive growth period (called the stretch phase), and any defoliation or pruning during this phase stunts its growth severely.

Vegetative Stage Defoliation & Pruning

Topping

When: after your plant has a total of 5 or 6 nodes


Topping is probably the most popular pruning technique available. It involves cutting your main branch right after a node (pair of leaves + growth sites), so that the remaining growth sites can turn into stronger branches. This allows cannabis plants to “bush out”, since topping breaks the tendency of the plant to grow into a Christmas tree shape. Topping is highly recommended, and if you haven't yet you can learn how to top in this article. 

Topped cannabis seedling on white background

Cannabis seedling that was recently topped


Veg Stage Defoliation

When: after 4 to 8 weeks from planting your seed


At this point, many leaves and small branches will have appeared, inhibiting your plant's ability to absorb CO2 and light in the center of the canopy. This is why it is important to defoliate and prune the middle of your canopy at this point, giving your plant the structure it needs to continue growing. On top of this, it is also important to start training your marijuana plant at this stage, if you haven't yet.

Vegetative cannabis plants ready to be defoliated

Cannabis plant with many shaded leaves, ready for defoliation

What to remove: if your fan leaves aren’t catching direct light, it means they are consuming more energy than producing it, and are also blocking airflow through the plant. Therefore, it is recommended to defoliate all fan leaves that are shaded by 2 or more leaves above them, and all fan leaves that are already touching the bottom side of another fan leaf (in direct contact). 
Cannabis plant full of leaves, in need of defoliation
Cannabis plant right after undergoing defoliation

Before and after defoliation on a vegetative cannabis plant

You can then continue defoliating and pruning your plants every 2 weeks after that, up to 5 days before flipping to flower (it is important to give your plants at least 5 days to recover from the stress before you flip them to flower). If you are growing outdoors, you can continue defoliating and pruning until about the middle of July, at which point most plants will start automatically switching to flower.


" Wait, what are FAN leaves? "


"Cannabis plants only have two types of leaves…"


Fan Leaves vs Sugar Leaves

Fan leaves - these are the larger leaves that come out directly from the branches. Fan leaves are the symbol of cannabis (although we hardly use them) and their main function is to collect light and CO2, store nutrients, and transpire.

Sugar leaves - these are small leaves that stick out of the buds and are covered in trichomes (hence the name). They are much smaller, and their main function is to store nutrients for the flowers and grow trichomes to attract pollen (they still collect light and CO2, and transpire, but not as much as the fan leaves).
Cannabis flower with purple tones, with arrow showing the sugar leaf vs the fan leaf

Fan leaves (7-fingered leaves) vs sugar leaves (single-tip leaves)


Veg Stage Pruning

When: after 4 to 8 weeks from planting your seed


Pruning and defoliation often go hand in hand. It is much better to prune at the same time as you are defoliating because they are both stressful activities for the plant.


What to remove: on many nodes (pairs of shoots), one shoot will be much larger than its opposite pair. In these cases, prune the small growth site so that the larger one can grow into a stronger branch (you can leave the leaf behind if it is still catching light).
Defoliating the stronger growth site of a cannabis plant's node

Prune the smaller shoot to allow its larger pair to grow stronger

Also, prune all shaded branches that didn’t make it to the outer 12" of the canopy and are now covered by other leaves and larger branches. Marijuana plants put more energy toward the branches that can more easily photosynthesize, which is why shaded branches are given less energy and end up becoming popcorn bud.

Prune shaded branches to allow larger ones to grow stronger


In a nutshell

The goal of defoliating and pruning during the vegetative stage is to set up your canopy for success during the flowering stage. For this, you need a strong base with thick branches, and a well-distributed foliage to allow for the most airflow, light penetration, and thus photosynthesis. 

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Flowering Stage Defoliation & Pruning

1. Day 20 to 25 after flowering

Most strains will go through a vigorous growth period between the time you flip them to flower and the 3rd week of flowering. While it is really important NOT to defoliate your plants during these 20-25 days of the stretch phase, it is equally as important to trim them back after this period is over. This is the last chance you have to prune any unwanted growth or leaves before your plant starts filling up with flowers. 


NOTE: NEVER top your cannabis plants during the flowering stage, as this will only stunt your flower production.

Cannabis plant with many leaves and ready for defoliation and pruning

Weed plant after the 3rd week of flower ready for defol

First, defoliate all bottom leaves and growth sites that aren’t catching any more light and that are blocking the airflow from the bottom to the top (first video). This is important because if you leave too much of a cluster behind, you will end up with a lot of larfy popcorn bud after harvest. Then, make sure to defoliate the leaves at the top that are blocking the lower bud sites from light exposure - this ensures they develop into dense colas in the future (second video)

Defoliating and pruning after the 3rd week of flower

Defoliating a cannabis plant to expose the shaded tops


Cannabis Lollipopping

A great technique that can be used at this stage is called “Cannabis lollipopping”, where you defoliate the bottom half of your plant, leaving only about 8” to 12” of canopy at the top. Lollipopping is great after the 3rd week of flower, as it helps clear out small growth sites that would otherwise become popcorn bud. 


In order to accomplish a lollipop, just choose the height you want to lollipop at (8” to 12” from the top), and then defoliate all leaves and growth sites below that line. Lollipopping is highly recommended indoors, where the light intensity is significantly lower the farther away your leaves are from the light source.   

Before and after defoliating and lollipopping a cannabis plant in flower

Lollipopping: the shaded leaves and branches were pruned


2. Pre-harvest defoliation

1 week before harvest time, your cannabis plant will have put on most of its weight and will start focussing on filling up its trichomes with cannabinoids. This is when most of your pistils are brown and the trichomes are going milky and amber. It is recommended for you to do one last defoliation (no pruning) at this stage for a few reasons.


1. It helps uncover those lower buds and sugar leaves that have been shaded by a big fan leaf for the last 4 to 6 weeks. 


2. It causes a mild stress on your plant and forces it to allocate all of its resources to the buds, which results in more trichome and cannabinoid production. 


3. It saves you over 50% of the time trimming because most of your fan leaves will have been already removed.

Cannabis plant in te flower stage 1 week away from harvest and ready for defoliation

Weed plant 1 week away from harvest and ready for defoliation

Cannabis plants that were just recently defoliated, 1 week before harvest with large flowers

Cannabis plants after pre-harvest defoliation

Cannabis flower full of white trichomes inside an indoor grow

Cannabis bud after pre-harvest defoliation


In a nutshell

The goal of defoliating and pruning after the 3rd week of flower is to set your plant up for success during the flowering stage. And the goal of defoliating and pruning on the last week of flower is to expose the lower buds and create enough stress for the plant to put out all remaining trichomes, as well as to make it easier for trimming later on during harvest. 

Want to train your plants like the ones in this article?

Here are some amazing products to help you out!


" Now that we know WHAT to do, HOW do we do it?"


" Easy peasy! You can use pruners (recommended) or just your fingers."  


How to defoliate & prune with scissors

The Slide'N'Snip technique

1. Start by pinching the leaf or branch with your non-dominant hand;

2. Place the tips of the open blades somewhere on the stem, and close the blades just enough to touch but not cut into it;

3. Run the blades all the way down the stem until it stops at the branch and can’t go any further;

4. Close your blades and cut the leaf or branch you want to prune;

5. Pull the leaf or branch off with your non-dominant hand.

Using the Slide'N'Snip technique on cannabis leaves


This technique is great because it doesn’t require you to see exactly where you need to cut. Watch this video for a quick demonstration of how to do the Slide’N’Snip technique.

How to defoliate & prune by hand

NOTE: for best results, use rubber gloves to avoid contamination from your hand to the plant. If you don’t have gloves, make sure to thoroughly wash your hands. Secondly, if you are pruning older branches that have already become hardened, do not prune them by hand as this will damage the surrounding area.
The Pinch’N’Bend technique

1. Start by pinching the leaf or branch at the base of the stem;

2. Bend the leaf or branch down by 90 degrees until it cracks (if it doesn't crack, twist it with your fingers back and forth to weaken it);

3. Pull the leaf or branch off.

This technique is super fast and easy to accomplish, and anyone can do it. However, during the late flower stage (when the buds are thick) it is NOT recommended to use your hands as you can damage your buds when pulling them off.
Holding a cannabis leaf about to be removed, with BudClips in the background

Pinch the leaf or branch by the base and you can more easily break it off


And you are done!


Defoliating and pruning are super simple and easy - but remember: you can always defoliate and prune more, but you can never put leaves or branches back on. 


For this reason, always take less than you think is necessary!


Learn to Grow Like The Pros

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But wait... I still have some questions!


" Q1: What is the difference between defoliating and pruning indoors vs outdoors? "

" Hint: it all comes down to light exposure and airflow "


Defoliating & Pruning Indoors vs Outdoors

1. Light Exposure

Our sun is nearly 100 million miles away, which means that it doesn’t matter if your plant is a few ft taller or shorter - the bottom and the top leaves will feel no difference in light intensity (as long as they are not in the shade). However, when it comes to indoor lighting, the intensity of your grow light decreases a lot as you get farther away from the source - from 5 to 10 times weaker every foot of distance away.


What this means is that training cannabis indoors is more about optimizing light distribution at the top, such as maintaining a flat canopy and defoliating the bottom of the plant (like the plant on this diagram). When growing outdoors, however, you don’t need to worry so much about this - just make sure to choose a spot in your backyard that has the most amount of sunlight, all day long, and you can have leaves from top to bottom (just not in the middle!).

Indoor light intensity diagram comparing a defoliated and trained plant and a non-defoliated and untrained plant

High-intensity vs low-intensity zones for indoor lighting. Image source.


2. Airflow

Airflow is essential for plants to absorb CO2 as it helps circulate the air released by the leaves (which is full of oxygen) and renew it by air that is full of CO2. For this reason, it is equally important to train indoor and outdoor marijuana plants to maximize airflow around the leaves and inside of the canopy.


The main difference, however, is that outdoors plants have the extra pressure from pests while indoor plants generally don’t. This is why we highly recommend defoliating outdoor plants at least once a month to clear out all old leaves that are turning yellow, not catching any more light, or that are blocking airflow to the middle of the plant. As long as you don’t create pockets of clustered leaves, you should be safe from the pressure of pests!

Cannabis plants during the flower stage outdoors after

In a damp backyard like this, defoliation helps keep the pests away


" Q2: How do I defoliate autoflowering weed plants? "



" The answer is simple: you don’t! "


Defoliating & Pruning Autoflowers

Autoflowers only have around 30 days in the veg stage before they automatically go into the flowering stage (AKA “auto-flower”), so it is best to avoid defoliating as much as possible, and only cut yellow or brown leaves, or bud sites that are really small and in the middle of the canopy. 


It is also not recommended to defoliate more than 10% of your autoflowers’ leaves at once, and definitely not recommended to top them, otherwise the stress can be too much and the growth will be stunted.


The only time when it is recommended to defoliate your autoflower cannabis plants is 1 week before harvest (the pre-harvest defoliation mentioned above). This allows you to avoid too much trimming after you harvest, and forces all of those trichomes and cannabinoids to come out due to the added stress at the end of the cycle.

Cannabis leaf with a Nitrogen nutrient deficiency

On autoflowers, only remove sick leaves and small shoots

However, it is not all doom and gloom for autoflowering marijuana plants. Autoflowers are the best candidates for low stress training, which is the most popular training technique and helps increase your airflow and light exposure the same way. Here is a full article on how to low stress train your cannabis plants. 


" Feels like we're missing something... How do I know this is all true? "


"Fair enough! How about some good old science to explain it all?"  


The Science of Cannabis Defoliation



Why does defoliation & actually increase your yields?



It all boils down to 3 vital leaf functions and a common enemy they are fighting.


The 3 Key Functions of Cannabis Leaves

1. Light Absorption

One of the main purposes leaves serve is that of catching light and using it to convert water and CO2 into oxygen and sugars through photosynthesis. In this context, then, leaves serve primarily as solar panels and the more exposure to light they have the more photosynthesis they will be able to contribute to the plant. Conversely, if leaves are completely covered or shaded, they will not be able to photosynthesize. It would be the same as putting one solar panel on top of another - the bottom panel won’t catch light.


This is why it is important to prune leaves and branches that are shaded by 2 or more other leaves on top of them, or that are touching one another. 

20 Photosynthesis diagram showing light, carbon dioxide, and oxygen around a weed plant
Photosynthesis process on cannabis leaves. Image source.

2. Transpiration

Transpiration is the process by which water vapor and oxygen (for us to breathe) leave the plant through the stomata - these tiny little openings under the leaves - while CO2 comes in from the air, thus allowing the photosynthesis process to happen. In fact, 95-99% of all the water that plants consume through the roots go back out into the air through the leaves while only 1%-5% stays in the plant and gets converted into sugars. This means that if your plant consumes 1L of water per day, it is "vaporizing" around 950-990 ml back into the air.

Stomata Diagram showing how CO2 goes in and Oxygen comes out
Stomata functionality - how transpiration works at the leaf level

So why do plants waste so much water? Well, it's not really a waste. Something else that happens while all of this water comes up from the roots is that the stems, leaves, and flowers take up all of the nutrients in it. So via transpiration, plants are pulling water from the ground, filtering out the nutrients and a little bit of that water for photosynthesis, and evaporating the rest of the water into the air (while taking up CO2).


This is why it is so important to prune everything that is blocking airflow within your plant, otherwise the humid air can never be carried away and exchanged for dry air full of CO2 again.


3. Nutrient storage

Another purpose that leaves serve is storing the nutrients they just absorbed from the water, so that they can use them later. Nutrients like N, P, K, and Mg are mobile, meaning that your plant can remobilize them from the old leaves to the new ones if they are suffering deficiencies. 


For example, when the leaves at the bottom of your plant start to go yellow, they are simply "donating" their stored Nitrogen to the new leaves, shoots, and flowers at the top. 


That’s why having a certain amount of green and healthy leaves is always important - it helps your plant remobilize those stored nutrients to its most vital parts. If you strip your plant naked like some folks do, you leave no buffer for it to mitigate nutrient deficiencies.

Healthy and dark green cannabis leaflets in white background
Healthy cannabis leaf - the perfect tone of green

The Enemy: Microclimates & Photorespiration



Avoid these and you will be set


Microclimates

Microclimates are little pockets of air in different parts of your growing space that are different from the overall climate you set. For example, you can set a temperature of 26C/79F and RH55% in your fancy exhaust fan, but if you measure the middle of your canopy you will end up with a cooler temperature and higher RH.


Microclimates are most common on the corners of your growing space, the underside of your canopy, and in the middle of the canopy where it’s humid. Since these areas are usually more shaded and have less airflow, they make the perfect environment for pests to thrive in and the worst environment for photosynthesis to happen - this is why it is so important to defoliate clusters of leaves in the middle of your canopy and avoid microclimates.

Cannabis tent with 8 flowering plants and arrows pointing to where the microclimates are
Microclimates: cannabis leaves clustered together

Photorespiration

Plants don’t just absorb CO2 during photosynthesis, they also absorb oxygen “by mistake” in a process called photorespiration - where instead of producing sugars, they consume sugars - becoming smaller instead of bigger. 


Have you ever noticed how small and light-green the leaves inside your canopy are? That’s because there is too little CO2 and so the leaves are respiring more than transpiring, i.e. consuming more than producing.


In other words, when you have a microclimate your leaves are consuming all of the CO2 available around them until there is no more, at which point they are forced to increase photorespiration and decrease photosynthesis. 

Clustered cannabis Leaves with dark shades in the middle
Clustered leaves lead to photorespiration

To summarize: shade + stale air = less CO2 + less light = more photorespiration + less photosynthesis = smaller plants/leaves/bud sites + more pests


In a nutshell

Leaves are useful for 1. Light absorption, 2. Transpiration, and 3. Nutrient storage. 


In order to make your leaves work hard you need to avoid microclimates because they stunt growth and attract pests. 


The more light penetration and airflow you can get in the middle of your canopy, the better your results will be.


Don't be afraid!

It is very common for new growers to fear defoliating and pruning their cannabis plants. After all, you are hurting them by cutting it up. But if you start slow and follow the rules you just learned, you will always have great results!

Happy growing, friend!

Want to continue learning? Here are a few more lessons for you!

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