Bud Rot on Cannabis Plants, Everything You Need to Know

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In this article, we are going to cover everything you need to know about bud rot on cannabis plants. From what it looks and smells like, how to fix it and most importantly, how to prevent it. Maybe you are here because you have found bud rot on your cannabis plants. Maybe you’re here because you want to find the best ways to prevent bud rot. 

Whatever the reason for your visit, we have everything you need to know, right here in this guide. If you have any questions about bud rot, and you need help, feel free to post in our cannabis forum

Let’s begin by explaining what bud rot actually is. If you would like to skip to any section of this article, please use the contents here:

What is Bud Rot?

Bud rot is the term used when a certain type of mould called botrytis infects a cannabis plant. Botrytis is a type of fungus that feeds on living and dead plant matter. It spreads quickly and can be devastating to a grower. 

It all begins when a small mould spore called a “pock” travels on a breeze and lands on your plant. From there it travels around the plant looking for a way into the softer tissue inside it. 

To be able to move around the plant, the pock needs moisture and condensation. If it has enough moisture, and it also finds a way into the soft plant tissue, the pock will germinate. It will then grow and begin to spread. 

Once it has started, the only way to stop it is by stopping the spread of more spores. This is done by removing and buds infected with bud rot.

Bud rot on cannabis plants, white fuzz on bud of cannabis plant, cannabis growers forum,

What Does Bud Rot Look Like?

When botrytis takes hold of a bud, the bud will begin to die. It will not take long before the bud begins to lose its vibrant colour and it will begin to look dead, and rotten. The later stages of bud rot are easier to identify. But by then the bud rot would have spread further, and grown more. You need to be able to identity bud rot as early as possible.

Early Signs of Bud Rot on Cannabis Plants

Early signs of bud rot can begin with a single leaf that is turning yellow. If every other leaf on your plant looks healthy, but there is one leaf coming out of a bud that is yellow, it may be bud rot.

Early sings of bud rot on a cannabis plant, what is bud rot, percys grow room, cannabis growers forum,
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Check the bottom of the stem of that leaf. If it leads into a brown or grey patch on your buds, rot is very likely. You should pull on the yellow leaf to see if it comes away from the bud easily. If it does, you need to inspect the bud closely to see if you find grey mould on the inside.

Later Stages of Bud Rot on Cannabis Plants

The later stages of bud rot will look like your buds are covered in a white fuzz. Many growers have experienced this, and it is devastating. This grey mould could be on one single bud, or many.

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If you find even just one bud that is infected with botrytis, you should check the whole grow for more! At this stage, the mould spores will spread around the grow room looking for more buds to infect. Bud rot on cannabis plants spreads quickly. It can ruin a whole crop in a matter of days.

What Does Bud Rot Look Like Under a Microscope?

This is what bud rot looks like under a microscope. It is tiny, very light, and can spread on the breeze easily. As the wind hits these spores, the small pocks are released in the same way flowers release pollen. 

The pock will travel on the breeze until it lands on something. Maybe the floor, the grow room walls, pots, or your plants. In many cases, the pock will not germinate, but if the conditions are right, it will. Then the mould will begin to grow and spread further.

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Does Bud Rot Have a Smell?

Bud rot does have a smell. But it is hard to smell it over the pungency of cannabis flowers. Up close, you may be able to smell the bud rot, and it will smell like any other mould. Slightly earthy, you will know it when you smell it.

You do not want to go around sniffing mouldy buds though. Breathing in those spores can be harmful to your health, so avoid doing that at all costs. You can identify bud rot easily just by looking at the plants. There is no need to try smelling it.

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Why Does Bud Rot Happen?

Mould spores are everywhere, but they will only germinate and begin to spread in the right conditions. Bud rot happens because a mould spore found a nice place to live, with the right environment.

When a mould spore lands on your plant, initially it can’t do anything. But with enough moisture and condensation it is able to move around the plant. The pocks (mould spores) will try to find an easy way to the soft tissue of the plant. This is often found in a broken stem, removed leaf, or damaged bud. 

Once it is inside the plant, it will germinate and begin to spread more spores. They will also grow, and produce even more spores. So the problem will grow exponentially.

How Does Bud Rot Spread?

Botrytis will take hold of the plant from inside at first. But as the mould grows, it will make its way out to the outside of the plant. This exposes it to air currents. The tiny mould spores will then be lifted onto the breeze and carried to another location. In a grow room, this could be another bud or plant.

If the conditions are right, the spore will find a way into the plant and germinate. Then the whole process begins again.

fruit infected with bud rot, botrytis, grey mold,

How Common is Bud Rot on Cannabis Plants?

Bud rot is very common, and sometimes can not be avoided. Botrytis mould spores can get inside big buds. Inside the big buds moisture can build up, and the air isn’t moved around. This allows the spores to just sit there and grow! 

The biggest buds in the grow room are the most susceptible to bud rot. And of course, those buds that get infected are not fit for consumption in any way! It will take your biggest buds, and destroy them. This is why every grower should be extra cautious in the late flowering stage. 

Bud rot can also be more common at certain times of the year. Temperature fluctuations and high humidity will encourage mould to grow. As summer moves into autumn, mould is more likely, so be extra vigilant around this time of year.

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Does Bud Rot Ruin the Whole Plant?

Bud rot has the potential to spread quickly, and that can ruin your whole grow. Whether that is one plant, or 20! But if found early, Bud rot can be removed from the grow room, and the risk of spreading is massively reduced. 

It is easy for more mould to pop up elsewhere on the plant. If you have found any bud rot on your plants, remove the infected bud immediately. The rest of the plant should be fine, but check over it carefully to make sure there isn’t any more rot. 

Where Does Bud Rot Start?

Bud rot will start on the inside of a cannabis plant. It will find an easy way into the plant’s soft tissues and continue to grow from there. 

Sometimes a mould spore will land on a flower early in the flowering cycle, and nothing will happen. But then as the bud grows, it will grow around that mould spore. This traps the air, and makes it stale. The mould spores love stale air. The moisture builds up, and the spores germinate and begin to grow. 

Once the mould is growing it won’t take long before the whole bud is rotten. If it is not removed from the grow room quickly, the mould will spread onto other buds.

Can Bud Rot be Fixed?

Unfortunately no. Any bud that is infected with bud rot must not be consumed in any way. This means no edibles, no oils, and definitely no smoking and vaping. 

The only way to fix bud rot is by preventing it from spreading any further. So if you do find bud rot on a cannabis plant in your grow room, the infected bud must be removed immediately.  

How to Treat Bud Rot on Cannabis Plants

If you have found bud rot a cannabis plant in your grow room, first of all, condolences. It is never a good thing to see on your plants. Many growers have been there, we all have to learn this lesson at some point. All you can do now is prevent it from spreading any further, and learn how to prevent it happening again in the future. 

To remove mouldy buds for your grow room safely, follow this guide. 


Turn off All Fans

The mould spores from bud rot are very light. They will travel easily on the slightest breeze. As soon as you touch that infected bud, the spores will be released into the air. So turn the fans off before you begin to reduce the spread of those spores. 


Wear Protection

It would be a good idea to wear a mask, you do not want to breathe in any mould spores. Also wear some latex gloves. Only touch the infected bud with these gloves, and once you’re done with them, take them off. Do not touch any other parts of the plant with these gloves, you do not want to spread the spores further!


Cover Infected Bud

The whole bud is no good. It must be removed. I know this might be a difficult thing to read, but the bud really isn’t safe for consumption. It has to be removed. 

Cover the infected bud with a bag. Paper or plastic, it doesn’t matter. You’re just trying to reduce the spread of any more spores. Once covered, you can also place some tape around the bottom to seal the bud into the bag.


Cut the Infected Bud Off

Now there is very low risk of the spores spreading any further, so it is time to cut the bud off and remove it. Simply take a pair of shears or big scissors, and cut the bud at the stem.

Take the bud out of the grow room and dispose of it. Get it as far away from the grow room as possible. 


Check Buds Thoroughly

Mould can spread quickly, and it can be hard to see in its early stages. Remove the gloves you were wearing and wash your hands. You need to inspect the plant for any more signs of bud rot. Remember to look out for a random yellow leaf, with a brown or grey patch in the bud it stems from. 

If you find more bud rot, then repeat the steps above and remove the mouldy buds. If you have inspected the plants, and you can’t find any more mould, then the next step is to clean the grow space.


Clean the Grow Room

After you have removed all the bud rot from the grow room, you should clean it thoroughly. Take the plants out of the room if possible. Clean the walls, floors, and ceiling. Wipe down the blades of fans, and any other surface you can that could be holding mould spores. 

When the room is clean and dry, put the plants back in, turn your fans back on, and you’re all set to go. Just keep a close eye on the plant in case more mould arises.

Now you just have to make sure it doesn’t happen again.

How to Prevent Bud Rot on Cannabis Plants

The first thing you can do to prevent bud rot is by growing a strain of cannabis that is mould resistant. Some plants are more susceptible to it than others. 

Over the years, cannabis breeders have selectively bred cannabis plants to be more resistant to mould and other pathogens. It is always a good idea to start in the right place. So check out the strain you want to grow, make sure it is from a respected breeder, and it is mould resistant. 

But don’t forget, these strains of cannabis are mould resistant, they are not immune, you still have to keep the plant in the right environment. 

How to Prevent Bud Rot Indoors

To prevent bud rot indoors, good airflow and extraction is essential! There needs to be a constant breeze circulating around the whole grow room and plants. If the air is not circulated properly, pockets of stale air will build up. You will also need to have adequate grow room extraction to exhaust used air.

Keep the air moving, and extract old air and vent it away from the grow room. Then you are less likely to see bud rot on your plants. 

Try to keep the room humidity of the grow room below 55%, and try to prevent any major temperature fluctuations. Going from warm air to cold air quickly can raise humidity.

How to Prevent Bud Rot Outdoors

Preventing bud rot outdoors can be tricky. If the plants get rained on a lot, the likelihood of bud root taking hold is much higher. It is important to keep large amounts of moisture off the plant. This can be done by using a cover, or simply shaking the plant a little after a rainstorm to shake off big raindrops. 

There should be plenty of air flow around the plant. Make sure your plants are not too close to a fence or wall. This will allow for good air circulation around the plant. 

Use a mold resistant strain if you’re growing cannabis outdoors. You should also try to grow a strain that flowers quickly, and finishes before it gets too far into autumn. 

Will Bud Rot Spread Whilst Drying?

Yes, as long as there is moisture in the buds, the mould can continue to spread. Make sure when you are drying your buds, there is always a light breeze moving air around the grow room. You should also ensure no buds are touching each other, or the walls of the grow room. 

If air can circulate around the buds whilst they are drying, mould spores are less likely to germinate.

Bud Rot in Dried Cannabis

If you think you have cannabis that is infected with mould then you can check it under a microscope to see. You may have smoked some, and it taste strange. Very earthy, with a horrible flavour. The buds would also have crumbled up easily when you touch it. 

If you suspect cannabis you’re smoking is mouldy, then stop using it straight away. Check It with a microscope and look out for long white strands in between the trichomes:

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Is Bud Rot Dangerous to Humans

Yes, and it is more common in cannabis than you think. One of the main reasons you should grow your own cannabis is because of things like this. Some commercial growers, and legacy market dealers will sell mouldy cannabis to you, and not care about it. 

Even big legal cannabis companies have been known to send out cannabis extracts infected with mould spores. It can happen to anyone. If mould spores get into your lungs, they may germinate. This can cause serious health problems. Ingesting mould in any way can make you very ill, do not do it. 

Is Bud Rot Smokable?

Absolutely not! You may see videos of people washing powdery mildew off buds using h2o2 and other chemicals. Bud rot is not the same thing! The mould is deeply embedded into your buds and can not be washed away. 

Those mould spores are part of the plant matter now, and it must not be used. Especially for smoking or vaping! It is very important, do not risk your health.

To Summarize Bud Rot on Cannabis Plants:

Finding bud rot on your grow is devastating. But it is something all growers go through at some point. It is part of the journey, I know it can be horrible, but just consider it as a lesson we all have to learn, it will happen less often now you know about it.

You now know what bud rot looks like, and how to remove it from your grow room. But most importantly you now know how to prevent bud rot!

Make sure you always have a good stable environment in your grow room. Keep the air moving at all times, keep the humidity below 55% and always be on the lookout for random yellow leaves. 

But remember, any bud that is infected with botrytis is not to be consumed in any way! Throw it away, or put it in the composter. At least then the worms can enjoy it. Also, if you need any help trying to identify if your plants have bud rot, just ask for help in our cannabis growers forum!

6 thoughts on “Bud Rot on Cannabis Plants, Everything You Need to Know”

  1. I’m confident that I had some rot in one of my outdoor plants. I followed the steps outlined in the above PDF and think I managed it alright. If the plant itselft is within a week or two of harvesting, would it be a better bet to chop a bit early and prevent more rot from forming or should I risk letting it go a bit longer?  Unfortuneatly, I didn’t have my phone on me when I first noticed it and I cut it out right away before taking any pictures.  

  2. @macky thanks for the article, I wasn’t looking forward to putting a post asking about the topic. I have removed 3 buds from one of my current plants based on what you wrote which sucks because I am right at the point of harvest!

  3. Ive smoked alot of moldy weed in my stupid teens years one tht was pure black found a draw in my trouser pocket tht got washed out but was gagging lol it wasnt nice but it did work for me at the time ngl i felt more mentally ill then physical tho from it! Nice article man! be re-reading this a few times in flower stage im sure xD  

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