Cannabis 101 

Cannabis education and information on ways to consume, how to grow or harvest, and more.

Bud Rot: How to Deal With This Cannabis Plant Mold

It doesn’t get much worse than walking into your garden or drying room to find mold developing on your plants and buds. Mold is something gardeners must always be aware of as the spores are virtually everywhere. Because mold is always ready to strike, it’s important to know how to prevent its development in the first place.

There are multiple types of mold that can infect your plant. The two most common are bud rot (botrytis cinerea) and powdery mildew. This tutorial will focus on dealing with bud rot, but if your current bane is powdery mildew, learn how to eradicate that and other plagues in this article.

What Is Bud Rot?

Bud rot is a type of mold that develops in the dense cores of the cannabis buds. The infection starts on the stem inside of the bud and then spreads outwards, making it very difficult to detect in its early stages. After its onset, bud rot breaks down the surrounding bud and spreads out in all directions. Soon it produces its own spores that can then spread to other areas of the plant or garden. The rot will first appear white and wispy and will turn grey and black as the bud turns to a mushy, slimy consistency.

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Once a bud begins to mold, it is no longer safe for consumption and must be discarded. Common practice is to remove the infected area of the plant and to let the rest of the plant continue to grow. However, if the infection is widespread, it might have to be completely removed from the garden to protect the rest of your crop.

Preventing Bud Rot in the Cannabis Garden

Hydroponic Marijuana Growing in Temperature Controlled Greenhouse

The best way to prevent bud rot is to understand what makes the mold thrive in the first place. Bud rot thrives in environments and plants with:

  • High humidity
  • Mild temperatures
  • Poor ventilation
  • Dense foliage
  • Dense buds
  • Weak plant immune systems

Bud rot prevention begins with the type of strain you select for your garden. Sativas, having adapted to humid equatorial regions, tend to grow light, wispy, airy buds. With improved air flow in the buds, sativas often have superior mold resistance. Indicas, on the other hand, adapted to the dry mountainous regions of Asia, and grow denser buds that are more susceptible to mold if introduced to a humid climate. If humidity control is a concern, consider growing a plant that expresses itself with more airy, mold-resistant buds.

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Pruning and training your plants can also help prevent bud rot. Humidity and ventilation are both impacted by how dense and crowded your canopy is (think walking through a dense jungle versus an aspen grove). By pruning your plants effectively, you increase the airflow, thereby reducing moisture collection. Training your plants increases further ventilation by pulling the colas apart from each other so they are not touching.

Plants with healthy immune systems are more likely to fend off mold growth. Growing organically with the use of compost tea and diverse nutrients can help increase beneficial microbes in the soil that help keep the immune systems of your plants strong and ready to fight against infection.

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Lastly, protecting your plant from excessive moisture is key in the battle against bud rot. Watering plants in the morning helps prevent humidity in the garden when the sun goes down or when lights turn off later in the day. Additionally, protecting plants from rain by growing in a greenhouse or indoors lends a huge advantage against bud rot. If your outdoor garden was just hit by heavy rainfall, it’s not uncommon for gardeners to use leaf blowers to help wick the water off of the plants. A simpler method is to walk through your garden and lightly shake each plant to remove the standing water.

For greenhouse or indoor gardens, fans and dehumidifiers may be used to regulate humidity. Using moisture monitoring devices is the best way to ensure that your grow room doesn’t have a humidity level conducive to bud rot.

Preventing Bud Rot in the Drying Room


Efforts to prevent bud rot do not stop once the bud has been harvested. Mold can also occur as the buds dry and cure. Here are a few tips to keep in mind.

As you harvest your crop, check your plants’ colas for rot. Again, if you find mold, discard the infected area while saving what is unaffected.

Harvest after a dry spell. If growing outside, it’s ideal to harvest when it hasn’t rained for a few days so that the buds have a lower moisture content.

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Pull off fan leaves and trim buds before drying. Doing so before hanging them up to dry will reduce the moisture in your drying room and increase the airflow to the drying buds.

Leave space between hanging branches as they dry. Allowing space between the colas and branches in your drying room will allow for better ventilation. You may also place fans around the room to create better airflow and use humidifiers to pull moisture out of the air.

Create an optimal drying environment. When drying, a dark space with humidity around 50% and a temperature of about 70 degrees Fahrenheit is generally recommended.

Adjust drying speed if necessary. Generally speaking, drying is not something you want to rush as THCA is still converting and the chlorophyll is still breaking down. A slow drying process is generally associated with a tastier and smoother smoke. However, if you’re finding mold in your harvested cannabis, speeding up the drying time by increasing temperature and decreasing humidity could save the rest of your crop from mold growth.

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If bud rot was found in your garden, anyone who’s processing your crop must understand the need to look for mold. Anything that is at all questionable should to be set aside to be inspected with more scrutiny to protect the end product’s consumer.

Mold can be detrimental, but it is also preventable with the right tactics and attention to detail. But don’t get discouraged if a little mold shows up in your garden! Many large-scale outdoor farmers have to assume a percentage of loss due to mold as it is difficult to prevent entirely. Remember to check your garden daily, think where and when the mold would likely show up, and trust your instincts. Remember, with practice comes mastery!