Mold on Marijuana Plants

Introduction: What is mold on pot plants?

On improperly stored marijuana, you may see white spots on cannabis leaves.   White mold on weed is a sure sign one is about to lose some money and a good high. Mold is a name for several species of fungus that affect plants like marijuana, including the two most infamous forms of mold, botrytis cinereal or bud rot, and the mysterious powdery mildew. Before we get into the details, let’s get right to the point: If you find moldy weed, THROW IT OUT. Do not attempt to salvage it. It may be deadly, not because mold is rare, but because inhaling concentrated mold can produce deadly symptoms.

moldy marijuana
Figure 1.

 How Does Weed Leaf and Bud Get Moldy?

The simple answer to how does weed get moldy is that mold is everywhere. This fungus has taken over the world. Ever put a closed package in the fridge only to come back and see that it has gotten moldy?  It was in a locked bag, in a closed and cold refrigerator, where does the mold come from?  The mold was already there. It’s everywhere. All it needs is time, food, water, and a decent temperature and it will live out its life cycle and even reproduce, using your precious food and weed as a substrate.
whitepowdery mildew on cannabis
Figure 2.

Types of Molds on Infected Marijuana

  1. Botrytis (bud rot)
  2. Cladosporium
  3. Mucor
  4. Penicillium
  5. Rhizopus

During Growing

white powdery mildew on cannabis
Figure 3.

When your weed is growing, there are mold spores around, but they will not grow and mature unless conditions are right. They like a damp, warm climate. Indoors. So, with an inside grow, it’s most important to make sure the humidity is low and the air continues to circulate. Marijuana, in general, is a hearty plant that produces its own defenses against mold when grown correctly. If you keep your air filtered, the temp warm and dry, and your plant healthy and bright, you can avoid encountering mold that will eat your plant. The truth is, mold tends to take over a plant which is in danger of dying, to begin with, so if mold appears, even if it hadn’t, excessive moisture or lack of circulation would still have resulted in an unhealthy plant. Early appearing mold is like a scavenger. It’s activating because it thinks your plant will soon be dead anyway. Bud rot starts inside your bud and is not visible, but as it grows, it produces discoloration, yellow, white, brown, and black spots. As the disease takes over, the spots may turn darker.

Some strains of weed are naturally resistant to marijuana. So, if you grow outside or indoors in an area susceptible to mold, try growing a mold-resistant strain. You can check for high mold resistance such as in the Cannatonic strain on our website here:

During Storage

does weed go bad
Figure 4.

Even if your marijuana made it through growth and drying without mold, you’re not out of the woods yet. Some marijuana takes on the mold during the curing and storage process. To avoid this, you need to make sure the cannabis is properly dried first. Then, you can use various storage methods. The most popular is the plain dark mason jar packed tight to reduce the presence of the moisture and oxygen molds need to grow. These jars need to be opened regularly, in the beginning, to exchange old air for new. If you want to get fancy, you can use products like Cannador and CVault. These products use absorbent material to keep the moisture levels perfect to prevent mold and decay. You need to store in a cool, dark place.

The Causes of Mold

  1. Wet conditions
  2. Improper humidity levels
  3. Lack of ventilation
  4. Improper watering
  5. Bad growing location
  6. Improper storage
  7. The wrong type of storage container
  8. Wrong time of storage environment
  9. Too much moisture and air in a storage container

Why Leaves with Mold are Bad to Smoke

Smoking moldy weed can cause health problems from allergic reactions to poisoning with toxins produced by molds. Moldy weed smells like mildew and even the first sniff may cause a cough or sneeze.

Moldy weed is not always visible to the naked eye. When researchers ran this seemingly clean batch under a microscope, they saw thousands of little dots that indicate mold:

moldy marijuana
Figure 6.

In 1988, mold on weed was associated with a fatal case of fungal infection of the lungs (Hamadeh, Ardehali, Locksley, & York, 1988). It should be noted this patient had leukemia and a bone marrow transplant and therefore was immunocompromised. So, if you are immunocompromised as many medical marijuana users are, it’s critical to make sure your weed is extra-clean. Most buyers can do this by getting a lab analysis from their dispensaries.

Smoking Moldy Weed Symptoms

  • Cough
  • Has bad smell when smoked
  • Fungal infection of the lungs
  • Asthma attacks
  • Breathing difficulties
  • Pneumonia
  • Headache
  • Throwing up
  • Diarrhea
  • Erratic heartbeat

What Does Moldy Weed Look Like?

bud rot
Figure 7.

What Does Moldy Weed Look Like?

  1. White Spots
  2. Black spots
  3. Discolored fuzz
  4. Discolored buds
  5. Discolored leaves
  6. Shriveled leaves and stems
  7. Mildew Smell
  8. Glows under black light
  9. Looks like discolored dots under microscope

How to Detect Moldy Buds

To find out if your weed is moldy, first, get a lab analysis from your supplier. Second, use a magnifying glass to look closely at the buds for white, black, or yellow dots. Use a black light to make any mold glow conspicuously. Use the picture above of the weed with mold under the microscope and compare that with what you see. Don’t mistake your trichomes for mold. Trichomes = good, mold = bad. Moldy buds will smell like mildew, urine, and musty clothes. It may smell like lavender if the mold has opened up some terpenes and processed some sugars, but it’s nothing you want to smoke, eat, or use in any way. You even have to be careful where you toss it out to make sure it does not contaminate other plants. If you have bought moldy cannabis, report it to your dispensary and get your money back. You will save yourself and you might even save someone else by identifying a bad batch. Dispensaries are profit-driven, but weed, due to its peculiar legal status, is particularly susceptible to a bad word of mouth reports, so dispensaries are quick to want to fix their errors.

botrytis marijuana plants
Figure 8.

Figure 9.

Social Media Wisdom

Mold on weed social

Figure 10.

getting rid of mould on weed.

Figure 11.
We always want to check with our friends on social media to get a real opinion on moldy weed. This buyer didn’t have visible mold when he bought the product, but it was damp. Likely, the mold had already started growing within the buds. The consensus, in this case, is correct, throw it out immediately.

Conclusion: How to Avoid and Prevent Mold

Avoiding moldy weed is generally about keeping your humidity around 50% or what is appropriate for the stage of growing or storage your plant is in and ensuring adequate ventilation and the overall health of your plants. You can also choose a mold-resistant strain like Cannatonic. Grow in a warm, dry area with a good breeze or a fan and exhaust. Test your humidity frequently. Regularly monitor your weed plants’ health. Invest in a pocket microscope and a digital humidity reader. Keep your humidity levels perfect and mold spores will be unable to grow.

A good, clean batch of Indica is the night time, stuffy-head-fever-so-you-can-sleep Nyquil weed you need to get over your stress. So, have a good look at your weed, then a good toke!


Hamadeh, R., Ardehali, A., Locksley, R. M., & York, M. K. (1988). Fatal Aspergillosis Associated with Smoking Contaminated Marijuana, in A Marrow Transplant Recipient. Chest, 94(2), 432-433. Retrieved 10 24, 2018, from

This article about Medical Marijuana was published on and updated on October 27, 2022 . Medical facts in this article was checked and article was medically reviewed by our . Author of this checked article is
Need to Pass a Drug Test?
Toxin Rid 10 Day Detox Program
Aloe Toxin Rid Shampoo + Zydot Ultra CleanMega Clean + PreCleanse Pills
Powdered Human Urine
toxin rid cannabis detox kit
Aloe toxin rid and zydot ultra clean
MegaClean THC detox drink
Powdered Urine Kit
$189.95 $209.99$235.90$69.95$43.95
More information
More information
More information
More information