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What Is Bud Rot And How To Deal With It

Bud Rot: A Grower’s Worst Nightmare! Learn Now How to Deal with Grey Mold

August 11, 2021

Pathogens, including bacterias, viruses, and fungi, are present in all living things.

These microscopic molecules are required for us to survive, and some can be harmful and cause a variety of problems. 

Cannabis plants are no different and can get infected by deadly particles. One of the worst is called bud rot, also known as grey mold or botrytis.

It's a fungal disease that can completely take over a marijuana crop. 

If you're a grower, it's vital to know the causes, signs, and how to control cannabis bud rot to ensure a healthy yield.

Continue reading to find out more about bud rot and how to protect your precious plants.

Bud rot - the most common cannabis mold

Even the most experienced growers can face the problem of bud rot in weed. It's hard to avoid because the fungus can travel through air, water, clothing, animals, and clones

What causes marijuana bud rot?  

The fungus and marijuana plants thrive in the same environment. Grey mold prospers in humid and cool temperatures. 

Bud rot doesn't care if the plant is still sprouting or fully mature. It’ll attack anything in its way and spread fast. As soon as you realize there's a problem, it's present, and many of your crops might be dying.

Looking for bud rot
Looking for bud rot

What is bud rot?

Bud rot is a mold that Botrytis cinerea, a fungus, causes. It's a common problem with cannabis, so the weed-growing world named it "bud rot." It describes what the fungus does to the plant; rots buds from the inside out. 

Outside the cannabis world, gardeners refer to it as grey mold because of its color. The fungus enters the plants through vulnerable areas such as the roots, wounds, tears, fresh cuts from pruning, or insect damage. 

What does bud rot look like?

Bud rot usually attacks young stems, as they're more fragile. The first signs begin right where the sprouts meet the soil. The typical bright green stems will be dull and soft, which means they're experiencing damping off. 

That doesn't mean that your more mature plants are safe from bud rot either. As soon as the fungus attacks, it’ll take whatever it can get and kill larger crops. 

Bud rot signs start with white color and a fluffy texture, like powdery mildew, and will be inside the buds. As it matures, the fungus turns to a dark greyish mycelium mass, and the stems of your plants will be soft. You'll see grey spots all over infected cannabis. 

Bud rot can show itself in other ways as well. Here are some other signs to look out for. 

bud rot
Bud Rot

Discolored buds

If one area of buds is starting to look dry or discolored, look at the stem for grey mold. The buds will have patches of black, grey, or brown. The texture will be dry and crumble easily. Even if all other parts of the plant appear healthy, it doesn't mean it's safe. 

On mature plants, the fungus will attack the wettest parts first because it loves humidity. The leaves closest to the water mister or farthest away from the air supply are at risk. 

Dark and dried up colas

The cola is a cluster of buds that are tightly together. It forms on the upper section of the main stem. If the cola is dark brown and looks dry, it could be a sign of bud rot. 

Yellow leaves

Before the discoloration, leaves can start to wilt. As the grey bud rot mold matures, the leaves will go from a vibrant green to yellow due to a lack of chlorophyll. Then, they'll become slimy and limp. 

The fungus sucks all of the nutrients out of the plant, causing it to die. 

How to treat bud rot

If you notice some of these signs in your cannabis plants and are afraid the bud rot will take over your harvest, don't panic yet. There are ways to treat the problem before it's too late. 

You'll need to move fast, as the pathogen infects at an exponential rate. Bud rot can kill a whole garden in just one week. Don't know what to do? Watch the video below and keep reading to find out more about the bud rot cure. 

1. Remove all affected buds

When the fungus is present, it's not about saving the infected plants. Instead, your goal is to protect the healthy crops from the pathogen. You'll need to remove all affected buds. 

In some cases, that means trimming a few leaves off the stem. Other times, you'll have to remove a whole plant; roots, stem, and all. 

During this stage, it's vital not to let any fungus touch other crops. You might need to take the pot out of the environment before pruning. 

Removing Bud Rot
Removing Bud Rot

2. Ensure the rest of the plant is Bud Rot Free

Once you take care of the obvious, it's time to be an inspector. Bud rot moves quickly, so it's possible it's in other parts of the plants that aren't very visible. 

Take the time to search and see if all crops are bud rot free. That's the only way the problem will stop, and you can continue growing healthy plants. 

3. Let the Buds Continue to Ripen (If You're Certain the Environment is Fixed)

During the next few days and weeks, keep an eye on your harvest. Let the buds ripen and grow as they should. If you see any grey mold appear again, you'll need to repeat steps 1 and 2. 

4. Harvest the Plant Immediately (If You Can't Fix the Environment)

In some cases, the bud rot can take over your whole growing area. As much as you remove the infected areas, grey mold is still in attack mode. 

When this happens, you'll need to harvest all mature leaves and move them to another area. You’ll need to discard the rest. 

Empty the soil and clean containers thoroughly with a disinfectant. Clean the space by wiping down the walls, tables, tools, and any other material you use while growing. Let the space air out to remove the moisture. 

From there, you'll have to start from day one with new soil and seeds. 

How to prevent bud rot

It's much more effective to prevent a problem with your cannabis plants than try to fix one. For example, if you never gain weight, you'll never have to worry about dieting to lose it. The same goes for mold. Here’s how to prevent bud rot. 

Creating the right environment and maintaining it will assist the health of your cannabis crops. 

In the garden

The garden is where the growth happens. Cannabis likes a humid environment, which is why it's so prone to a pathogen attack. Bud rot also thrives in moisture. Regardless, there are ways to manage the space to please the marijuana and keep fungus at bay. 

Monitor humidity

The ideal humidity during vegetation is 40% to 70%. Once the plants start to flower, you should reduce the level to 40% to 50%. Then, as the plant matures, you can drop the humidity to 40% or lower. 

You use a hygrometer to measure the percentages in the garden. To maintain the right levels, use a dehumidifier or have a ventilation system for airflow. 

Be aware of any puddles or still water in the growing room, as the fungus can grow here and then pass through the air to plants. 


Pruning leafy plants is a way of preventing bud rot. When leaves are close together and touch, it creates wet spots. Trimming bigger leaves will give the others room to breathe and dry out between watering. 

Leaf Pruning
Leaf Pruning Can Avoid Bud Rot


Training a plant is when you control the direction it grows. Usually, you do this with a pole, and as the stem gets bigger, the farmer ties the two together. 

Training helps manage plants and is ideal for indoor gardens. It reduces the cause of bud rot because you can make sure the plants aren't touching or growing into each other. There's enough airflow from plant to plant. It also assists in reducing the spread of bud rot. 

Try a different watering schedule

You never want puddles of water or a too moist environment. If you notice your plants are constantly damp, you might want to change your watering schedule.  

Reduce the number of times a day you water so that the cannabis can drink up all the H2O on the soil. Remember, at different humidities and times of the year, plants behave in varying ways. 

You can test different schedules and see which one is best for your plants and environment. 

Amend nutrients

Soil amending is when you add material into the earth to make it an ideal place for crops. Without this, your plants might be sucking up too many nutrients from the ground, leaving them vulnerable to infection. 

Once the nutrients are gone from the soil, your plants will also become weaker with the lack of food. Your cannabis won't be strong, and if bud rot appears, it’ll attack quicker. 

Amending nutrients will increase the soil's quality, which keeps it and the crops strong and fed. This is a great way to prevent bud rot from making a home in your garden. 

In the drying room

Once the marijuana leaves reach their total growth, farmers must harvest them. Before they're ready to be smoked or processed, they must dry out. 

The garden is a humid, warm oasis, while the drying room is quite different. Bud mold after harvest is still possible. The fungus can creep into your drying room and strike. We're going to go over ways on how to keep this stage bud rot free. 

Harvest buds when dry

When it's time to harvest your weed, make sure the leaves are dry. You'll know your watering schedule, so plan accordingly. 

By doing this, you reduce the risk of bringing fungus into your drying room, as it loves wet places. If you notice some leaves are damp, shake them or give them proper airflow before leaving the garden. 

Remove fan leaves

Removing big fan leaves when mature will help reduce bud rot. These spread out and can clutter the garden. If they're too big, they can abstract airflow. 

Taking fan leaves to the drying room will ensure your sizable healthy crop stays that way and creates space for the smaller plants to grow. 

Leave space between buds

Even in the drying stage, you'll want to leave space between each bud. This is for two reasons. The first is to ensure proper airflow so that the marijuana can dry efficiently. The following explanation is that chance bud rot is present, so it won't jump from leaf to leaf with ease. 

The fungus hates dry and cool areas, so it might die before it can infect all the crops. 

Create the perfect drying environment

The drying process takes about 15 days, depending on the environment. The ideal temperature for a drying room is about 68℉ or lower. You don't want anything warmer because the cannabinoids and terpenes can evaporate. 

The humidity level should reduce down to 40% or lower. The idea is to take out moisture slowly. To manage the levels, make sure there’s quality airflow around the room. Never blow air directly on the leaves, but instead use a ceiling fan on low or use a window for natural breeze. 

You want to create a dark place for a better quality product. The chlorophyll will preserve better, and that affects the taste. 

Ensuring your drying room is perfect will help reduce bud rot because the fungus cannot survive in these conditions. 

Healthy AK47 Marijuana Plant
Healthy Cannabis Bud

Stop bud rot before it starts!

Doing things right the first time around will save a lot of headaches in the future. If you're a new grower, understanding all these details can be overwhelming, but not paying attention will result in problems. 

You’re unlikely to have a problem with bud rot if you follow the preventative steps and continue to monitor your crop. Attention to detail and patience will help you grow healthy mature marijuana, bud rot free, that you can enjoy recreationally or sell if your location allows. 

Now you know what bud rot is and what a nightmare it can be. If you have a plant or fifty on the go, head out and check to make sure everything is in place. If you're a new grower, start planting. 

What are you waiting for? You know how to prevent bud rot and the perfect ways to ensure healthy growth. All that’s left to do is buy some seeds and get planting!

About the author: Parker Curtis

Parker Curtis has around a decade of cannabis-growing experience, specialising in soil-less and hydro grows. He’s mastering outdoor, greenhouse, and indoor grows.

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