Medically Reviewed by
Jason Crawford

Article Last Updated on January 12, 2023

Despite this being a common problem for weed bought on the black market, you can also end up with moldy cannabis if you grew it yourself, and even if you purchased it from the local dispensary.

Moldy weed is a subject we’ve covered a few times in our previous articles. We’ve written about whether weed can get moldy and what molds actually look like on weed plants. And since mold is a huge problem for both cannabis growers and cannabis users, we decided to give you more information on the subject.

This article will go into how you can spot mold growth on weed buds, and give you an answer on whether smoking moldy weed can affect your health and well-being, so let’s get started.

What Are Mold and Mildew?

Molds are a group of fungal species which grow anywhere with excessive amounts of moisture and warmth. They reproduce through airborne spores and aren’t harmful in small quantities since our immune system protects us, though they can be a danger to our health if consumed in large quantities. Mold growth typically develops in the form of fuzzy or slimy spots which can be white, blue, green, black, brown, or gray. 

Mildew, on the other hand, is the growth of long filamentous structures, hyphae, which present themselves as fuzzy white thread-like structures all over the surface of food, plants, and other organic matter. Mildew has a cotton-like appearance and typically grows on the surface of organic matter, so it can be removed more easily than mold.

Even cannabis plants aren’t immune to mold and mildew and once they spread, they can destroy your plant and even your whole batch of weed plants. 

Mold Development in Cannabis Plants

The breeding ground for moldy weed is often a result of increased humidity and warmth in unventilated grow rooms, especially in the early growth stages. Similarly, mold can develop once weed that hasn’t been properly dried is stored in mason jars or airtight containers. Since mold spores survive high temperatures and reproduce fast, it isn’t easy to get rid of them. Some of them even produce mycotoxins that are carcinogenic, so knowing how to differentiate between a moldy plant and a healthy one is essential.

Types of Mold and Mildew Commonly in Cannabis

There are over 10,000 mold species, though some of the most common include Alternaria, Aspergillus, Botrytis cinerea (bud rot), Cladosporium, Mucor, Penicillium (Penicillin), Rhizopus, Stachybotrys chartarum (black mold), and others. However, cannabis plants mostly develop the following types of mold:

  • Aspergillus;
  • Botrytis Cinerea;
  • Cladosporium.


This is a fungus that can’t be destroyed by heat, so you won’t be able to get rid of it by lighting a joint or decarbing the weed. It produces mycotoxins which are harmful to the human body.

Botrytis Cinerea

The next type of mold is Botrytis Cinerea, otherwise called bud rot. This is the type of mold which develops if the plants have excessive amounts of moisture trapped inside the colas, develops from the inside, and spreads throughout the plant. If your plant is suffering from grey mold, you’ll notice dying leaves, limp colas, and maybe even cobwebs. 

To check for bud rot, inspect the colas, and if you see any that are affected by botrytis, remove them in order to preserve the plant.


Another common type of mold that develops on cannabis plants is the Cladosporium. While this plant doesn’t produce harmful mycotoxins, it can cause harmful side effects when ingested by cannabis users. Cladosporium is often found paired with other types of mold, such as Aspergillus or Penicillium, and can have olive green, brown, or black color.

Powdery Mildew

The most common type of mildew that forms on weed plants is the powdery mildew and it’s often mistaken for young trichomes. It first develops as grey or white patches on the plant which eventually turn yellow, brown, and black. Powdery mildew is often caused by grow rooms with little to no airflow, and if not removed on time, it can spread and ruin your whole cannabis yield.

What Happens if You Smoke Moldy Weed?

Smoking weed of good quality results in the consumption of cannabinoids, such as THC and CBD, which are used to treat a lot of medical conditions. However, if you smoke moldy cannabis, you can experience a number of harmful side effects. Unventilated, overly humid, and warm grow rooms are the ideal breeding ground for mold spores which can cause a series of harmful effects to marijuana users. 

A 2017 study shows that Aspergillus is one of the most common types of mold found on cannabis plants. Smoking this mold can cause a fungal infection called Aspergillosis which weakens the immune system and can lead to coughing, fevers, chest pains, and difficulty breathing. 

Cannabis can sometimes be covered with the mold Penicillium which causes an allergic reaction in people who are allergic to Penicillin. Similarly, Botrytis Cinerea can also cause an allergic reaction and lead to respiratory issues for some marijuana users. Cladosporium, on the other hand, can produce mycotoxins which cause fevers, asthma attacks, and even health problems such as lung infection (pneumonia) in some cases.

Moldy weed and weed covered in powdery mildew should be thrown out since it may contaminate all of your cannabis plants.

Checking for Mold on Cannabis Plants

Regularly inspecting your cannabis plants for mold growth is extremely important and can be the difference between a great yield or a yield that you’ll need to throw out. To check your plant for mold, follow the next steps:

  • Inspect your stash. Mold that has been developing for a while can often be detected by the naked eye. Powdery mildew is a bit more difficult to spot since the fuzz looks similar to kief and resinous trichomes, and if that’s the case then move on to the next step;
  • Check with a microscope or a magnifying glass. If the mold spores aren’t visible with the naked eye, you can take a look under a microscope, a jeweler’s loupe, or a magnifying glass. Another way to check is by using a black light on your buds – if they’re moldy, the mold will look extremely green under the light;
  • Smell the weed. Cannabis has a distinct smell as a result of the different terpenes which are present in the weed plant. Cannabis that has an unusual smell (wet, musty, etc) may have developed mold;
  • Compare your plant with photos of mold online (If you’re unsure whether your weed plant is moldy, compare your plant to moldy plants online).

Preventing Your Cannabis Plants From Getting Moldy

Since mold develops in moist and warm environments, maintaining ideal conditions in your grow room is paramount. Keep the humidity levels between 59% to 63% (or according to the guidelines for the specific strains you’re growing), and a temperature between 59-71°F.

Prior to storing your cannabis, make sure that it’s dried properly and the container is also completely dry. Store the container in a cool, dry place away from direct sunlight or at a temperature below 77 degrees Fahrenheit. 

Final Thoughts on Moldy Cannabis

Whether you’re consuming medical marijuana or you’re a recreational user, smoking moldy weed is never a good idea. It’s best to check your cannabis plants regularly, so if you spot mold or powdery mildew forming on the plants, remove it immediately to prevent it from spreading to your whole yield.

Make sure that you maintain optimal conditions in the grow room when growing weed plants – mainly the humidity levels, temperature, lighting, and nutrition. Tailor the growing conditions to the type of strain that you’re cultivating to get the best results.

Since mold also forms on improperly dried and cured weed, make sure that you allow your weed to dry completely before storing it in a glass jar or an airtight container. Store your dried and cured weed in a cool place, away from direct sunlight, and don’t keep it in the fridge or freezer since that can result in the development of mold.

Moldy weed can cause a lot of health problems, including a cough, fever, chest pains, difficulty breathing, asthma attacks, allergic reactions, and even lung infections, so making sure your weed is mold-free is one of the most important steps you can focus on as a marijuana user and/or grower.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.