The BudTrainer Method™ Lesson #5

How to Defoliate & Prune Hemp Plants

(works with AUTOFLOWERS)

Written by cannabis production expert Henrique Dias - Updated on Oct 1, 2024

The image shows a black fabric pot, labeled "Bud Pots," sitting on a wooden surface. The pot has yellow grommets around the top edge and yellow gardening wire securing a plant inside the pot. The plant, which appears to be a cannabis plant, has green leaves spread out on the table around the pot. The label on the pot indicates it is a "3 GAL" size and features the BudTrainer logo and tagline, "Grow like the pros." The scene seems to take place in an indoor gardening or cultivation setting.

DISCLAIMER: Everything taught and sold by BudTrainer® is to be used strictly for legal purposes. We condemn the production of illegal substances and it is your duty to ensure that you are complying with the law. The words "hemp", "cannabis", "weed", and "marijuana" are used interchangeably to refer to the same plant (legal hemp with less than 0.3% THC) for the purposes of this lesson.


The Surest Way To Increase Airflow & Prevent Pests

Did you know that nearly 100% of commercial cannabis producers defoliate and prune their cannabis plants? They wouldn’t be doing it if it wasn’t increasing their yields. In fact, if left unpruned, your plant can attract mold and bugs such as spider mites, thrips, and aphids. But if you defoliate and prune it properly it will yield bigger buds, more trichomes, and an overall larger yield (with no pests). So let’s get to work.

Tools & Materials

  1. Trimming scissors
  2. Disposable gloves
Trimming scissors beside disposable rubber gloves on top of a white surface

3 Stages of Cannabis Pruning & Defoliation

The BudTrainer Method™ has three stages of defoliation.

The first two stages are meant to help you clear out old leaves and leaves that are blocking airflow to the plant, in order to allow for more transpiration and thus more growth. 

The last stage, on the other hand, is meant to help you prepare your plant for harvest, giving it more light exposure during its last week and making it easier to harvest when the time comes.


1. Vegetative Stage Defoliation

When: week 5+ of the vegetative stage

Stage 1 of defoliation and pruning is meant to set up a strong canopy structure when your plant is young. By removing old and shaded leaves, and removing small branches, your plant transfers its energy toward the stronger branches and leaves left behind, thus promoting a much stronger base for your plant.

Growing Outdoors?

Stage 1 can be repeated every 2 weeks when growing outdoors.

Growing Autoflowers?

Skip Stage 1 if you are growing autoflowers, as they only get 4 to 5  weeks of vegetative stage time.

Black fabric pot labeled ‘Bud Pots’ in a 3-gallon size, containing a leafy green plant. The pot is secured with yellow garden ties, and additional gardening tools, including a yellow spool of wire and plant trimmings, are scattered on the wooden table around it. The background features soft blue lighting, adding to the indoor horticultural setting.


2. Flowering Stage Pruning & Defoliation

When: 3 to 4 weeks after switching to flower

Stage 2 of the defoliation and pruning process is the most essential stage. Performed after the flowering stretch phase, stage 2 is where you get to “clean up” the small and shaded leaves, but also all small bud sites that would otherwise form larfy, popcorn bud. You will leave behind only bud sites that can form big buds.

Growing Outdoors?

The process is exactly the same, but since you can’t know exactly when marijuana plants switch to flower, wait to defoliate until your plant has stopped stretching, and started forming bud crowns.

Growing Autoflowers?

Instead of performing Stage 2 in one day, prune and defoliate on a daily basis, only removing 3 to 5 leaves or branches in order to avoid stress.

A tall plant growing in a black fabric pot labeled ‘Bud Pots’ with a 3-gallon capacity. The plant is supported by yellow garden ties attached to the pot. The pot sits on a wooden table with trimmed leaves and gardening tools scattered around. The background is a plain indoor wall, creating a controlled growing environment.


3. Pre-Harvest Defoliation

When: 1 week prior to harvest day, or on harvest day itself

Performed one week before harvesting or on harvest day, Stage 3 is where you remove all fan leaves that don’t have trichome heads attached to them. This not only makes it easier to trim your buds later on, but it also helps expose the lower buds to more light for that last week of flowering, thus helping them reach the same maturity as the top ones.

Whether you are growing autoflowers or outdoors, Stage 3 is always the same.

A person wearing a plaid shirt and blue gloves hangs a large cannabis plant upside down for drying. In the foreground, another cannabis plant is standing upright in a black pot, supported by yellow garden ties. Additional drying plants are visible on the right side, creating an indoor harvesting scene.

BudTip: How To Defoliate Weed Like A Pro

With Scissors (branches & leaves)

This technique is essential for cutting branches, since you can’t remove them by hand. However, you can also defoliate your leaves with scissors in order to get cleaner cuts, while keeping your hands clean. Here is how to do it:

  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 the skin 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.
Close-up of a person wearing blue gloves using small pruning scissors to trim a plant stem. The image features instructional text overlay that reads, ‘1. Place scissors here’ with an arrow pointing to the base of the stem, and ‘2. Slide until stem & cut,’ with another arrow indicating the cutting motion. The BudTrainer logo is visible in the bottom right corner.

By Hand (leaves only)

This technique is super fast and easy to accomplish, and anyone can do it. However, it only works on leaves and not branches, as they have a more fibrous skin and don’t come off easily. Here is how to do it:

  1. Start by pinching the leaf at the base of the stem;
  2. Bend the leaf down by 90 degrees until it cracks (if it doesn't crack, twist it with your fingers back and forth to break it);
  3. Pull the leaf away from the plant until it comes off.
Close-up of a person wearing blue gloves adjusting a plant stem using yellow training clips. The image features instructional text reading, ‘1. PUSH PETIOLE (STEM) DOWN’ and ‘2. PULL AWAY,’ with arrows indicating the steps to train the plant. The surrounding green leaves and stem are clearly visible.

Now that you know how to remove your leaves and branches from your plant, it’s time to break this process up into the 3 Stages of cannabis pruning and defoliation. 

If you are growing autoflowers, you can skip straight to Stage 2.

Stage 1. Defoliating & Pruning During Veg

After 5 to 7 weeks from germination (1 to 2 weeks after topping), your plant will be ready to get defoliated and pruned (as well as trained, which you learned how to do in Lesson #4: How to Train Cannabis). 

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 means they will start consuming about as much energy from the plant as they produce, so they are not useful anymore. In fact, the older they get, the more energy they consume, which is why removing them is a good idea.


Step 1. Defoliating Main Stalk Leaves

Leaves and branches in the shade are also a net-negative in energy production, meaning they take more away from your plant than they contribute to it. Just imagine what would happen to a solar panel that is installed UNDER the roof, and not on top? The same is true for those small, shaded leaves and branches. So go ahead and, with your garden scissors, cut them off.

Top-down view of a plant with large green leaves, featuring yellow plant training clips along the main stem. The image includes instructional text that reads, ‘REMOVE LEAVES ON MAIN STALK,’ with arrows pointing to specific areas on the stem where leaves should be removed.


Step 2. Pruning Shaded Leaves & Branches

The main stalk leaves are the oldest leaves on your plant, and as much as they may look plump, green, and beautiful, it’s time to remove them so that your plant can concentrate on the other leaves. In fact, after removing these large and old leaves, your younger ones will become twice as large in a matter of only 1 to 2 days.

Close-up of a person wearing blue gloves using pruning shears to trim a low branch from a plant. Yellow training clips are visible on the plant stems. The image includes instructional text reading, ‘PRUNE LOW & SHADED BRANCHES & LEAVES,’ with an arrow pointing to the pruning area.


Step 3. Topping For The 2nd Time

Topping isn’t be anything new to you at this point, as you already learned how to top your cannabis plants on Lesson #3: How to Top Cannabis and again on Lesson #4: How to Train Cannabis. Topping is also considered a pruning technique, and this is where you get the chance to top your cannabis plants for the 2nd time. 

To top again, simply cut the top 1 inch from each of the 4 top branches, leaving behind 2 or 3 nodes on each (4 to 6 new growth sites each).

Close-up of a person wearing blue gloves using pruning shears to carefully trim the top of a small plant. The image includes instructional text that reads, ‘TOP 1 INCH AT MOST,’ with an arrow pointing to the area being trimmed. The surrounding green foliage and stems are clearly visible.

When topping for the second time it is important to only top the 4 top branches, and not the 4 bottom branches, as they already have to “work” harder to make their way to the top of the canopy. By topping only the top nodes, the lower ones can “catch up”.

A plant growing in a black fabric pot with yellow ties supporting the branches. The image includes instructional text reading, ‘ONLY TOP THE TOP BRANCHES (DO NOT TOP BOTTOM BRANCHES),’ with circles indicating the top branches to be pruned and X marks on the lower branches to avoid pruning. The BudTrainer logo is visible in the bottom right corner.

BudTip: Always Prune Dwarfed Branches

After the initial defoliation and pruning, inspect all remaining nodes and prune any growth sites that have become dwarfed when compared to its opposite counterpart. By removing the small growth site from the pair (as pointed by the white arrow below) you help your plant focus its energy on the larger growth site, instead of wasting it on a small branch that will never grow past the top of the canopy.

Close-up of a person wearing blue gloves using pruning shears to trim a small, underdeveloped branch on a plant. Yellow training clips are attached to the plant’s main stem. The image includes instructional text that reads, ‘PRUNE DWARFED BRANCHES,’ with an arrow pointing to the area being pruned.

Pruning & Defoliating Outdoor Marijuana?

If you are growing your plants outside, you can continue pruning and defoliating it on Stage 1 every 2 weeks. This will ensure your old leaves are consistently removed, allowing the new ones to capture more light and airflow. Not to mention, the pressure from pests outdoors is much greater, and this will help ensure your plant stays safe.

Close-up of a black fabric pot with yellow garden ties supporting the branches of a plant. The plant’s lower branches are visible, and the background shows an outdoor setting. The image includes instructional text that reads, ‘DEFOL & PRUNE EVERY 2 WEEKS OUTDOORS.’ The BudTrainer logo is visible in the bottom right corner.


Pruning & Defoliating Autoflowers?

Autoflowers do not need to be defoliated or pruned during the veg stage since they only get about 4 to 5  weeks of vegetative time. If you are growing autoflowers you can start directly on Stage 2, after 3 to 4 weeks in the flowering stage.

Stage 2. Defoliating & Pruning During Flower

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.

This is why Stage 2 of defoliation and pruning is the most important one. During this stage you will be selecting the final branches your plant will grow, removing everything that doesn’t have a good potential for growth. This is where you get to pick only the best tops in order to let them develop into high cannabinoid buds.


Step 1. Defoliate Shaded Leaves

Pick a line 12” to 18” from the top of your canopy, and defoliate all leaves and branches that start below that line. This means your leaves aren’t catching any more light and are blocking the airflow from the bottom to the top, and by removing them you will promote more growth up top.

A person stands behind a large plant growing in a black fabric pot labeled ‘Bud Pots.’ The plant is supported by yellow garden ties. The image features instructional text that reads, ‘BEFORE’ at the top, with ‘12”-18” FROM TOP’ and a dotted line indicating a section of the plant. Another arrow points to the lower part of the plant with the text, ‘DEFOL LEAVES BELOW THE LINE.’ Gardening tools are scattered on the wooden table in front.
A person stands behind a large plant growing in a black fabric pot labeled ‘Bud Pots.’ The plant is supported by yellow garden ties. The image features instructional text that reads, ‘BEFORE’ at the top, with ‘12”-18” FROM TOP’ and a dotted line indicating a section of the plant. Another arrow points to the lower part of the plant with the text, ‘DEFOL LEAVES BELOW THE LINE.’ Gardening tools are scattered on the wooden table in front.


Step 2. Prune Low Branches

During the stretch phase, your plant will also select certain branches to send energy to and certain branches to “dwarf”. These dwarf branches will never grow strong, and by removing them your plant sends even more energy to the strong branches left behind, while also having more room for airflow. So remove all dwarf branches whose tops are in the middle of the canopy, more than 6” below the top. They will often be much thinner than your strong branches, and easy to spot.

A person wearing a plaid shirt and a BudTrainer apron is using pruning shears to trim the lower branches of a tall plant supported by yellow ties. The image includes instructional text that reads ‘PRUNE LOW BRANCHES,’ with an arrow pointing to the area being pruned. The BudTrainer logo is visible in the bottom right corner.
A person wearing a plaid shirt and a BudTrainer apron is using pruning shears to trim a lower branch of a tall plant supported by yellow ties. The person’s hands are focused on carefully cutting the stem while adjusting the plant.


Step 3. Prune Shaded Growth Sites

Just as you pruned dwarfed branches due to poor light penetration and airflow, you can remove all growth sites (small clusters of pistils) that are more than 12” or 18” below the top of the canopy. This means they will never catch much light and will thus form into larfy popcorn bud, which is very undesirable. When you remove the small larf, your plants focusses even more energy toward your top buds.

Close-up of a person using pruning shears to trim a shaded growth site on a plant. The image includes instructional text that reads, ‘PRUNE SHADED GROWTH SITES,’ with an arrow pointing to the small growth being pruned. Yellow training clips are visible on the plant’s stems.

Stage 3. Defoliating & Pruning Pre-Harvest

One week before harvest time is when most of your pistils are brown and the trichomes are going milky and amber. We recommend 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.

A cluster of mature cannabis plants with thick buds, supported by yellow ties, indoors under soft lighting. In the background, other plants can be seen hanging upside down for drying, indicating a harvesting or curing process.

Defoliate ALL Fan Leaves

This part is easy - start with the largest fan leaves at the lower part of your canopy, and as you go up, remove ALL of them. If your fan leaves don’t have any trichomes on the leaf itself of the leaf stem, you can throw them out.

A cannabis plant with large buds and fan leaves. The image includes instructional text that reads, ‘DEFOLIATE ALL FAN LEAVES,’ with arrows pointing to the large fan leaves that should be removed. The BudTrainer logo is visible in the bottom right corner.

However, if your fan leaves are covered in trichomes, you can keep them aside for making hashish or extracting.

Close-up of a cannabis leaf covered in trichomes under bright lighting. The image includes instructional text that reads, ‘KEEP ALL LEAVES WITH TRICHOMES,’ with an arrow pointing to the trichome-covered leaves. The BudTrainer logo is visible in the bottom right corner.

While you can do the pre-harvest defoliation by hand, cannabis leaves tend to pull skin strings from your main stalk as you remove them like this. This can damage your lower buds, which is why we recommend using scissors to execute all of Stage 3. 


You Are Off To A Bountiful Harvest

In one week your plant will be more than ready for harvesting, and all you will have to do is chop it. Your lower buds will have been exposed to more light and thus reached maturity, and the amount of trimming left for you to do is minimal.

A person wearing a plaid shirt and blue gloves hangs a large cannabis plant upside down for drying. In the foreground, another cannabis plant is standing upright in a black pot, supported by yellow garden ties. Additional drying plants are visible on the right side, creating an indoor harvesting scene.

Behind the Leaves: Why Does Defoliation Increase Yields?

1. Light Absorption

One of the main purposes leaves serve is that of catching light, just like solar panels. The more exposure to light they have the more photosynthesis they will be able to contribute to the plant, and the bigger the plant will get. Conversely, if leaves are 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.

Diagram showing how leaves on top of eachother lose light absorption

2. Transpiration

Transpiration is the process by which water vapor and oxygen leave the plant through the stomata - these tiny little openings under the leaves. At the same time this happens, CO2 enters the leaf 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 1 liter of water per day, it is "vaporizing" around 950-990 ml back into the air. So why do plants waste so much water? 

Diagram showing how transpiration happens in the stomata of a cannabis leaf

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.

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.

A close-up of a cannabis plant with yellowing older leaves, showing signs of nutrient redistribution. The image includes instructional text that reads, ‘NUTRIENTS FLOW FROM OLD LEAVES TO THE NEW ONES,’ with an arrow pointing to a yellowing leaf. Green, healthy leaves are visible in the background.

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.

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About The Author

Henrique Dias with sunglasses on the head and a background of an indoor grow tent filled with cannabis plants inside the BudPots

Henrique, the CEO of BudTrainer®, is a mechanical engineer with a commercial cannabis production post-grad, and is also a former commercial cannabis consultant. 

H takes plant science principles and breaks them down into simple steps for home growers to achieve the same results as the pros and grow the highest-quality cannabis.

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