How to Tell If Weed Is Moldy

Moldy weed is not only bad-tasting but it’s also dangerous for your health, which is why it’s important to know how to tell if weed is moldy. Fortunately, most cannabis products sold at dispensaries are tested for mold before they hit the shelves, but mold can still develop after purchase if your buds are stored in a humid environment with poor ventilation.

Low-Tech Tests for Moldy Weed

The Sight Test

If mold spores are well developed, they should be fairly easy to spot with the naked eye. Whether you’re looking at buds or cannabis edibles, mold might look like:

  • Small white spots

  • Cobwebs (this could either be mold or spider mites)

  • White, gray, or green fuzz

Mold that’s still in the early stages can look like dusted kief. So, unless you’re buying moon rocks, a kief-like powder on your bud could be a kind of potentially harmful fungi.

The Smell Test

Even if you can’t see it, marijuana mold often gives itself away simply by the smell. If it’s well developed, the smell of moldy weed is usually similar to human sweat, urine, or hay. If you open a jar of cannabis or a packet of Seattle pre-rolls that you’ve stored for a long time and notice a distinct odor, presume mold and throw it away. It’s not a good idea to inhale mold on purpose, so if you’re not sure, use the other tests rather than getting up close and taking a whiff.

The Snap Test

Cannabis that’s properly cured should feel spongy and make a sound when it snaps. It shouldn’t crumble between your fingers or feel damp and limp. While you can’t take the buds out of the jar in licensed dispensaries, check the texture and sound of your weed as soon as you take it out of the jar at home. If it’s dry and crumbly or damp, suspect the presence of mold. 

High-Tech Tests for Moldy Weed


Small mold spores often have a similar appearance to cannabis trichomes, making it hard to tell the difference if you’re just looking at your buds with the naked eye. However, if you look at the buds under a small hobby microscope (these are inexpensive and are readily available online), spotting mold becomes much more straightforward. 

How to Tell the Difference Up-Close

Whereas trichomes have a sparkling, thread-like appearance with little heads and gaps between them, mold spores will look like a clump of green, white, or gray fuzz. If you use a black light, the mold will glow green. Even if you purchased your cannabis from a reputable dispensary and it’s unlikely you’ll find any mold, looking at the flowers under the microscope certainly makes for a fun experiment!

Testing Lab

If you’ve tried all of the tests described above and haven’t found anything wrong but are still experiencing mold-like side effects from your weed, you can have a sample tested at a lab. While this won’t be free, it will provide you with a lot of valuable information about the plant’s composition and the presence of any pesticides, heavy metals, yeast, other pathogens, or other substances that might be making you sick.

Some of the licensed cannabis testing labs in Washington State include: 

  • Confidence Analytics (Redmond)

  • Dragon Analytical Laboratory (Olympia)

  • Trace Analytics (Spokane)

  • The Werk Shop (Seattle)

  • Anatek Labs (Spokane)

  • Integrity Labs (Olympia)

How Mold Develops on Cannabis Plants

Mold is a kind of fungus that reproduces via airborne spores and can develop on cannabis plants at any stage of cultivation or storage. Moist environments with poor ventilation are especially likely to lead to mold development. Once the mold spores have settled on the buds or stems, there is no way to salvage the affected material.

The most common kinds of mold that you’d find on marijuana buds include Botrytis or gray mold (the fungus that causes bud rot) and powdery mildew. However, Aspergillus, Cladosporium, Cryptococcus, Mucor, Penicillium, and Rhizopus can affect cannabis plants too. Once developed, mold can throw off your weed flavor profile, reduce the potency, and even let off carcinogenic mycotoxins when smoked.

Health Effects of Moldy Cannabis

Smoking moldy weed is never a good idea. Depending on the type of mold, the health consequences can include:

  • Upper respiratory system symptoms, including coughing, wheezing, chest pain, shortness of breath, sinus pain, and nasal congestion

  • Nausea and vomiting

  • Fever

  • Lethargy

  • Allergic reactions

Typically, a healthy person will only experience unpleasant symptoms for a few days after they smoke moldy weed. However, the consequences for people with compromised immune systems can be far worse—Aspergillus, Mucor, and Cryptococcus fungi can cause very serious, potentially deadly lung infections: aspergillosis, mucormycosis, and cryptococcal meningitis respectively. No matter how much you paid for the buds, it’s simply not worth smoking moldy marijuana.

What to Do If Your Cannabis Flower Is Moldy

If you see or smell mold on your cannabis, there’s nothing left to do but chuck it. Smoking moldy weed is not worth the risk—even if you have a healthy immune system and your personal risk is low.

Once you’ve identified a moldy bud, carefully check all of the buds around it and discard all of the flowers that show even the slightest signs of mold development. In places like Seattle where cannabis is legal, you can simply throw cannabis plant material in the trash. If you decide to compost the buds instead, be sure to use a hot composting technique to kill the mold spores.

If you only just purchased the buds and found mold growth on them later on, go back to your dispensary and show them the mold so that they can recall the batch and notify the supplier. An honest dispensary will always give you a refund for moldy weed.

How to Prevent Mold

Cannabis mold that develops after purchase can be prevented through proper storage. To prevent moldy weed, store cannabis:

  • In dark-colored jars

  • Out of direct sunlight

  • At 59-63% humidity

  • Just below 77°F

To ensure the correct humidity levels, you can purchase disposable humidity packs or buy containers made specifically for the purpose of storing weed. Never store cannabis buds in the refrigerator or the freezer. The humidity levels and temperatures found in these environments create the perfect breeding ground for mold! If all else fails, go for Seattle cannabis concentrates instead. They have a much longer shelf life than buds.

Look for Mold, Prevent Mold Growth, and Never Smoke Moldy Weed

Even if you consider yourself to be a fun-gi (or fun-girl), avoid moldy weed at all costs. The health risks are simply not worth it, not to mention the terrible taste! When shopping for weed, go to a reputable dispensary, visually inspect the buds, check the lab report and testing date, and do the snap test when you get home. 

Then, keep your cannabis mold-free with proper storage, or better still—smoke it while it’s still fresh! If you still have any doubts about how to tell if weed is moldy, your local budtender will be happy to help.