Understanding Moldy Cannabis:
Risks and Prevention

How do you identify mold on cannabis?

A cannabis plant with mold on it will have diminished aroma, flavor, and sensory effects. You can’t always see the mold right away, but if your flower is starting to look discolored, it may be a sign of mold.

Eventually, the mold will make itself known visually. White powdery mildew will look just like that—white and powdery. It can be mistaken for trichomes, but powdery mildew tends to have a more sawdust-like texture. Other molds may look like dark spots on the plant or appear in spider web-like patterns.

Even if you can’t see it, you may be able to smell it. It will smell similar to other molds you’ve noticed on bread or cheese—musty, damp, and sour like mildew. Be careful here, though. Recently, a different kind of pathogen, an infectious RNA known as hop latent viroid (HLVd), is popping up on cannabis plants. It can also cause a damp smell similar to composting leaves. While it’s not mold, it can certainly make your plants more susceptible to mold outbreaks

What causes mold on cannabis?

It doesn’t take much for mold to grow. Mold spores are naturally present in the air. For them to reproduce, all they need is the right temperature, some moisture, and contact with organic material.

Moldy cannabis is generally caused because the plant itself grows in similar humidity and temperature levels to mold spores. The plant can act as the key third ingredient for mold growth—organic material—but so can things like dust, fibers, or exposed wood.

Maintaining a clean growing environment can help mitigate the risk of mold forming, but the risk can’t be completely eliminated.

What are the effects of moldy cannabis?

The effects mold has on your plants can impact the health of your employees and customers.

If your employees are exposed to moldy cannabis, they may experience symptoms like coughing, congestion, sneezing, wheezing, and nausea. Customers could also feel these side effects if the moldy bud makes it all the way to them. If they’re generally healthy and smoke it, they likely won’t experience negative side effects. But if they have a compromised immune system or are allergic to mold, the effects of smoking moldy cannabis can be serious.

If your market is medical, the stakes are higher. There’s a greater expectation for clean cannabis by consumers and regulators. Consumers use your flower for medicine and can experience worse side effects if it’s moldy than if a generally healthy person consumed it.

Regardless of the market, putting employees and/or consumers in danger is a quick way to ruin a business.

What are the risks of moldy weed?

Apart from the potential health issues your employees and customers could face, selling moldy cannabis could have a grave impact on your business and its bottom line.

For example, in 2024, one Massachusetts MSO was fined $200K for selling moldy weed. This scandal was brought to light by employees of the MSO and supported by complaints from patients and consumers, adding damage to the brand’s reputation.

Selling moldy cannabis also leads to a breakdown in trust between consumers, business owners, and regulators. Without trust and accountability between all three, state programs and the cannabis legalization movement in general suffer

How do you prevent moldy cannabis?

Preventing moldy cannabis starts with the fundamentals: have staff wear personal protective equipment (PPE) over their shoes and clothing to prevent the spread of outside contaminants, maintain a clean grow, and monitor your temperature and humidity levels.

Take prevention one step further by considering the physical structure of your grow. Installing compartmentalized ventilation can help avoid cross-contamination between rooms and growth stages while giving you greater control over temperature and humidity levels.

To prevent moldy cannabis from leaving your facility and landing on dispensary shelves, add a proactive decontamination step to your standard operating procedures (SOPs). Cannabis mold decontamination takes place after the flower is trimmed and before it’s sent off for testing. There are several types of cannabis remediation technology, though regulators often favor radio frequency (RF).

RF is an organic process that eliminates mold on cannabis plants by using long, low, non-ionizing wavelengths to penetrate the core of the bud. These wavelengths cause the water molecules within the plant to vibrate, creating enough heat and friction to kill mold DNA without damaging trichomes or changing the molecular structure of the plant.

With a designated step to decontaminate your flower, you virtually remove any risk of selling moldy cannabis. Think of it like the pasteurization step used for all dairy and nut products. It’s simply cleaning the product before putting it in consumers’ hands.