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  • Writer's pictureAaron Killion

How to Spot Mold on Cannabis and Avoid Poor-Quality Medical Marijuana

Do you know how to spot mold on cannabis plants? As a medical marijuana patient, you’ll need to know the signs—especially if you’re treating a condition that threatens your immune system, like cancer or HIV/AIDS. You shouldn’t run into a lot of moldy weed if you’re shopping at reputable dispensaries, but your supply can develop mold over time, especially if it’s stored in less-than-ideal conditions. Luckily there are a few telltale mold signs that you can easily spot.

How to Spot Mold on Weed

Two types of mold are especially common on marijuana: powdery mildew and grey mold (botrytis).

Powdery mildew is the easiest type of mold to locate on marijuana. It’s typically fuzzy and white, taking on the appearance of a white powder (hence the name). This type of mold can usually be spotted from a distance, though it’s still a good idea to examine your cannabis closely. You should always be on the lookout for wilting cannabis plant leaves, discolored roots, or dark spots.

Grey mold is a more subtle contaminant that causes bud rot. While it can live on the surface, it often exists deep inside the flower—invisible or faintly visible to the naked eye. If the leaves appear uncharacteristically dull or dry, or if the cola (the central cluster of the flower) seems soft and lifeless, you may have grey mold. If anything looks suspicious, you can pull apart the buds and take a closer look at the cola. Look specifically for a graying discoloration or the appearance of a subtle cotton-like growth. Both are common signs of grey mold.

Don’t Confuse Trichomes for Mold Growth

It can sometimes be difficult to identify mold on weed because the trichomes themselves can have a mold-like appearance to the naked eye—fuzzy, powdery, lightly colored, and delicate.

As you develop an eye for it, you’ll be able to distinguish mold from trichomes more easily, but if you have any doubt, you can use a magnifying glass to be certain. Under a magnifying glass, trichomes will have a crystalline appearance with tips shaped like small mushrooms. Cannabis mold spores just look fuzzy and dirty.

Identify Moldy Weed Using the Smell Test

If you’re still on the fence, or if you need to identify mold in a pinch, the smell test can be a dead giveaway. The cannabis plant is naturally rich in trichomes, aromatic plant oils that emit various scents. Depending on the strain, the cannabis may have an aroma that’s skunky, earthy, citrusy, piney, or fruity—or some combination thereof.

Mold, on the other hand, emits volatile organic compounds, which have a distinctly musty aroma. If you’ve ever been in a moldy basement, you know the smell we’re talking about: it’s foul, stale, and sour.

Moldy weed usually emits this type of musty aroma. If you notice it, it’s time to throw the cannabis away and purchase a new batch. You can’t kill mold simply by drying it out, so don’t try to salvage moldy cannabis.

If you’re a patient, consider shopping at medical dispensaries in your area (rather than recreational dispensaries). Because these facilities cater to people with diverse medical needs, they tend to take extra meticulous care in providing fresh, high-quality cannabis flower. If you have a qualifying medical condition and you live in Arizona, we may be able to help you obtain your Arizona medical marijuana card online via telemedicine.

How to Prevent Mold on Marijuana

When storing your medical cannabis, it’s very important to keep it in a dry, temperature-controlled location to prevent moldy weed. Never keep cannabis out in the open, especially in locations where the relative humidity exceeds 65%. Ideally, you’ll want to keep all fresh marijuana in an airtight container designed for cannabis storage—such as a waterproof cannabis storage jar. Avoid exposing cannabis to open-air environments as much as possible.

If you grow your own medical cannabis, you need to watch your humidity levels carefully. Through most of the grow cycle, you’ll want to keep the relative humidity below 70%. It’s also important to space your plants apart if you want to keep your cannabis mold-free.

In general, cannabis maintains its freshness for 6 months to 1 year. After that time, the cannabinoid and terpene content starts to degrade to the point where the product is no longer as potent or effective. In addition, old cannabis is more likely to contract mold and other bacteria simply because it has been exposed to the elements longer. So if your cannabis is over a year old, it’s best to just throw it out—even if it doesn't show visible signs of mold.

Maintain the Quality of Your Medical Marijuana

Mold identification is essential for medical marijuana patients. If you accidentally ingest moldy cannabis, you may experience dangerous reactions including fever, shortness of breath, severe allergy attacks, and upper-respiratory effects like wheezing and asthma attacks.

Smoking moldy weed is bad news. You shouldn’t encounter moldy cannabis very often, but if you do find it, you’ll be glad you identified it before consuming it.


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