bud rot weed

The Main Causes Of Bud Rot When Growing Cannabis

There are two types of mold that can affect your plant: bud rot and powdery mildew. Although both of them are types of fungus, bud rot can be considerably more harmful to your harvest than powdery mildew because it attacks directly our precious flowers, turning them black, and leaving smelly and for us unable to consume them.

1. What Is Bud Rot?

Bud rot is a type of mold that develops in the inside of the cannabis buds. The stems on the inside of the buds start with an infection that spreads to the outside, making it extremely hard to detect in the early stages.

After it has infected the inside of the buds, the rot starts spreading in all directions, producing spores that can spread to the other plants in our grow space or any other plants nearby.

2. What Does Bud Rot Look Like?

It’s really hard to detect bud rot in the early stages because the fungus starts infecting your plant from the inside out. In the early stages, bud rot affects the stems inside the buds which is hard to see from the outside but they will start to look gray and gooey.

As the rot starts to further infect the buds, you will see the leaves starting to yellow and wilt, and the buds starting to develop a gray web on top or white dust (it’s the spores) on top of them.

If you already have the dust and webbing, your buds are no longer able to be saved and your whole plant is probably infected also. This white spores are what infects the healthy parts of the plant and can be transferred from plant to plant by water, wind, and on your own clothes.

If you suspect your plants are infected with this type of mold, the best way to be sure is to look between the spaces in the buds and try to decide if something is wrong. If the inside of the bud is brown and mushy, you should isolate that plant and prepare to remove the part of the bud that is affected.

If most of the bud is compromised, the best thing to do is to throw the whole plant out and look for signs of infection in the rest of your plants, as bud rot spreads easily and can completely compromise your harvest.

3. How To Prevent Bud Rot When Growing

The best way to prevent bud rot is a combination of good growing conditions and the right maintenance of your plants. Bud rot thrives in growing rooms with high humidity, poor ventilation, and slightly warmer temperatures and can be easier to get if your plant is bushy, have very dense buds, or has weak genetics.

We can say bud rot preventions starts by selecting the best genetics for your grow space. Always look for highly-resilient plants and if you cannot offer them optimal growing conditions, opt for growing Sativa-dominant plants.

We recommend our new Orange Sherbet Auto, this Sativa-dominant will grow tall and wispy, very good for when you have problems with humidity.

Indicas are full of thick wide leaves and really fat buds, making it easier for bud rot to thrive. On the other hand, Sativas tend to grow less-dense buds and grow taller and wispy, making less probable to get bud rot. If you prefer Indicas, you have to know that they usually grow more compact and produce way more leaves than Sativas.

Know this in advance so you can prepare to perform light defoliation of plant training techniques to avoid bud rot.

Other factors that can influence the appearance of this fungus are failing to control the humidity level. As you may know, fungus thrives in the wet. A combination of a warmer temperature along with the lack of proper ventilation may cause water to not evaporate completely and increase the humidity levels.

This is one of the main causes of bud rot, so always check your growing conditions and adjust accordingly.

Be sure to have the right amount of fans and an exhaust proper for the size of your grow room to have good air exchange and have a hygro thermometer to check on the humidity levels and temperature inside your grow room.

If you grow outdoors, there’s not much you can do other than choosing the right place for your plants. Place them somewhere where they get a good amount of light and wind, and be sure to protect them from heavy rain so they don’t get wet for a long period of time.

Don’t let your plant grow in poor conditions, as this can result in a number of problems, not only bud rot.

4. How To Prevent Bud Rot When Drying

Even if you took all the cares necessary to prevent it, bud rot can appear after harvesting. Bud rot can also happen while drying and curing, that’s why it’s necessary to check the temperature and most importantly, the humidity levels.

The best way to avoid bud rot is to have an appropriate environment in your drying room, it is recommended to have a relative humidity of 60% and a temperature of around 15-25.

If you are having problems controlling the humidity in your drying room, opt for wet trimming instead of dry trimming. By wet trimming, you’re removing the excess plant material that contains water and will allow for better airflow and lower the humidity in the drying room.

Another good way to increase airflow is to leave a good space between the branches or even placing small fans to have really modest air circulation in the drying room.

To prevent your buds from molding while drying (or curing), always check your buds before hanging them to dry and never harvest after your plants have been watered ( for indoors) or after a rainy day (for outdoors). First, allow them to dry a little bit for a couple of days.

If you followed every single tip and could not avoid bud rot, you can also speed up the drying process. By providing more airflow you can dry your buds in considerably less time than 2 or 3 weeks.

Have in mind that this will drastically change the smell and flavor of your buds, leaving them smelling like dry hay. This is not recommended unless you need to take extreme measures to save your crop from bud rot.

5. In Conclusion

Bud rot can be a very nasty problem to deal with. It does not only spread to all your plants in the same room but also makes your buds turn gray and unsmokable. We recommend always having the best environment you can provide your plants to avoid problems.

If you’re tired of your plants getting mold, we recommend further adjusting your growing environment and trying with a more resilient strain, like our Gorilla Cookies Auto.

Bud Rot can ruin your yields, ruining your precious flowers. Find out how to prevent your buds from molding whilst growing and drying your cannabis plants.

How to identify and avoid bud rot

Copy article link to clipboard.

Link copied to clipboard.


  1. What is bud rot, and when does it occur?
  2. How do you detect bud rot?
  3. Can moldy buds be saved?
  4. How do you prevent bud rot outside and inside?

Just like the satisfaction of a home-made cake can spur some to learn baking, a home-grown joint can tempt many cannabis aficionados into becoming growers. For beginner cultivators raising healthy plants can be one of the steepest learning curves. The rapidity at which a rogue fungus or mold can destroy a plant is breathtaking. Infected buds can be destroyed in as little as a week .

The rapidity at which a rogue fungus or mold can destroy a plant is breathtaking. Photo by: Gina Coleman/Weedmaps

Image lightbox

One of the most common diseases new growers encounter is bud rot, also known as botrytis cinerea, or gray mold. Bud rot can wreak havoc on crops if left unchecked, so the ability to detect its signs early and prevent it will help ensure healthy plants.

What is bud rot, and when does it occur?

Bud rot is a fungal pathogen or a type of mold that develops in the heart of cannabis buds. While the appearance of the fungus often occurs in the later stages of flower development , it usually permeates the bud tissue at an earlier stage in the crop development but remains dormant. When the environment becomes conducive, the mold rapidly rots the buds from the inside by crumbling the surrounding layers, spreading out in all directions.

Usually, denser buds are affected, but in some cases, patches may become visible over the entire plant. As the mold spreads, it can produce and transmit spores to other plants. Mold can also become an issue after harvest during the drying process.

How do you detect bud rot?

If you’re new to growing cannabis and unsure of how to detect bud rod, here are some signs to look for:

Discoloration in and around the bud

According to Danny Danko, author of Cannabis: A Beginner’s Guide to Growing Marijuana , there are several giveaways that indicate the onset of bud rot. ”The first sign of bud rot will be a discoloration of flowers and the short leaves protruding from them,” says Danko. “The buds will have pockets of brown, gray, or black (dark purple) chunks that look dry and crumbly.” Danko recommends using a magnifying glass or loupe to examine buds.

Bud rot initially appears as pale, powdery mildew on buds, but becomes darker in color as the bud assumes a slimy consistency. When the mold has fully taken hold, the infected bud will easily separate, showing a dark, dusty interior. The dust is mold spores.

Dark or dried-up colas

The colas , or central flower clusters that form in the upper portion of the main stems, may also hint at bud rot. Colas which appear dried up or darker in color can indicate the presence of mold. A diseased cola will stand out in contrast to the healthy tissue of the plant, making it relatively easy for even newbie growers to see that something is amiss.

Colas which appear dried up or darker in color can indicate the presence of mold. Photo by: Gina Coleman/Weedmaps

Image lightbox

Yellow leaves

The sudden emergence of yellow leaves attached to colas can be a sign that there is mold at the base of the leaves. Yellow leaves with bud rot often fall out easily. Close inspection of the leaves may reveal mold spores close to the cola.

Can moldy buds be saved?

Once a bud begins to show signs of bud rot, it is unsafe for consumption and must be discarded. “In some cases, when discovered early, a grower can cut out the parts of the flowers affected by bud rot and reduce the spread,” explains Danko. “Use sanitized and sterile tools and clean them often to avoid spreading the spores.”

After the infected bud or buds have been removed, the rest of the plant can be allowed to grow. However, if there is a widespread infection, destruction of the plant may be prudent to avoid infecting other plants nearby.

How do you prevent bud rot outside and inside?

According to Danko, bud rot tends to be more prevalent in outdoor plants, such as those in climates with humid fall weather like northern California or the Pacific Northwest.

One of the difficulties of plant mold is that it is such a pervasive pathogen . Bud rot can be caused by several different hosts and it can survive for extended periods of time in crop debris . Awareness of the microenvironments and climates in which the fungus thrives can help prevent bud rot.

Danko advises that the best way to keep outdoor plants dry is to protect them from rain and morning dew, and place them far enough apart that they aren’t touching. “Cover the plants with a tarp, which doesn’t touch the plant tops, or use a greenhouse enclosure to keep them dry. If they do get wet, shake them so that pockets of moisture don’t form,” he says.

For those wondering does rain cause bud rot, the answer is that rainy weather fosters conditions conducive to bud rot. The problem is that high humidity and dampness accompany rain, supplying a source of moisture for mold growth on buds.

“Cultivators in areas prone to bud rot should consider growing plants that are more resistant to mold and powdery mildew,” states Danko. “Seeds can be purchased for plants that have acclimated to overly wet conditions.” Seeds that show mold-resistant properties or a higher tolerance to damp conditions include Durban Poison, Brazil Amazonia, and Colombian Gold.

Another option for wetter climates is timing your planting to avoid the onset of the rainy seasons. Auto-flowering cultivars , which start flowering when they reach a certain age, regardless of photoperiod, can be planted in the spring and harvested during the summer, before the wet fall season.

Danko also recommends removing some of the lower leaves that fan out on bushy plants to promote airflow beneath the canopy — this goes for both outdoor and indoor plants.

The best way to support indoor plants is by encouraging air circulation. An oscillating fan can efficiently keep air moving inside. “Use proper filtration for all air entering your room and seal off any places air can get in that isn’t filtered, such as cracks under doors,” explains Danko.

“Keep your grow room on the warmer side, between 70-80 degrees F and maintain a relative humidity of 40-50 percent.”

Nighttime temperatures should be 10-15 degrees below daytime temperatures so the flowers have a chance to cool down internally. This helps the root system in the same manner. Humidity at night for preventing mold should be 40% or lower.

Neem oil, which is a non-toxic oil derived from the neem tree , is a natural fungicide. It can be diluted and sprayed onto the plant to help ward off the fungi that promote bud rot.

It’s also critical to avoid bud rot after you’ve harvested your buds. Leaving space between hanging branches as they dry, creating an optimal drying environment, or even speed-drying, can help prevent the conditions in which mold spores thrive.

How to identify and avoid bud rot Copy article link to clipboard. Link copied to clipboard. Contents What is bud rot, and when does it occur? How do you detect bud rot? ]]>