Growers Network Staff

July 23, 2018 5 min read
July 23, 2018
5 min read

What California is Teaching us About the Impact of Mold

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In this article from Boveda, Rachelle Gordon teaches us how mold in California is teaching us valuable lessons about the importance of proper growing techniques.

The following is an article produced by a contributing author. Growers Network does not endorse nor evaluate the claims of our contributors, nor do they influence our editorial process. We thank our contributors for their time and effort so we can continue our exclusive Growers Spotlight service.


This article was republished with permission from Boveda. The original article can be found here.

Moldy cannabis isn’t safe to consume or smoke. Firing up moldy cannabis causes mold spores to spread. Trimming off the mold from your cannabis doesn’t fully eliminate the danger either. When in doubt, throw it out.

Mold is one of mankind’s biggest and oldest enemies. There are several different types of mold, many of which can make food unsafe to eat and homes uninhabitable. Depending on the type of mold present and the length of exposure, effects may be mild to severe, and can include coughing, trouble breathing, headaches, vomiting, diarrhea, heart palpitations, and infections in the lungs. People with asthma or compromised immune systems are most likely to be affected by mold, and could potentially lead to death.

Cannabis, just like any other type of produce, has the potential to develop mold. While some cases do appear in the cultivation process, the majority come after harvest, either during the drying and curing phase or in storage, when moisture levels are too high. Although most cultivators know how to prevent mold growth on cannabis, that doesn’t mean that every crop is perfect. Additionally, if an end user doesn’t keep cannabis in a cool, dry place, that stash could also be at risk.

Is legal cannabis completely mold-free?

Marijuana is now legal for medical and/or adult use in 29 states. Each state makes its own rules to regulate cannabis. Testing for mold and other pathogens, therefore, can be inconsistent.

Moisture safety guidelines for cannabis cannot come soon enough. In August 2017, Anresco Laboratories tested several cannabis plants, extracts and edible samples, all from the Bay Area. The results, first reported by San Francisco Magazine, were disturbing, to say the least. Nearly 80% of the cannabis samples tested positive for some type of pathogen; 15% tested positive for mold.

“We weren’t entirely surprised given the unregulated nature of the market for so long,” Anresco spokesman, Kyle Borland said. He added that while it cannot be certain that this round of testing was representative of the California industry as a whole, the results were still concerning.

Mold can also cause substantial financial losses for cannabis cultivators. Should a cannabis sample test positive, the entire batch may have to be destroyed. Because cannabis is still illegal at the federal level, many growers do not have proper insurance to cover these losses. This is why cannabis farmers strive to prevent mold in the first place.

Widely accepted best practices recommend that all cannabis that will be consumed as flow be stored at a 0.55-0.65 water activity level (aW). This can be achieved by storing flower in an airtight container which has a relative humidity (RH) between 55% and 65%. Maintaining this requisite aW throughout the supply chain, from completion of drying through merchandising, ensures safety and quality for the consumer.

Keeping cannabis between a 55% and 65% RH level also optimizes the potency, efficacy, flavor, aroma and taste of the flower. Testing has shown that when cannabis is stored within these proper humidity levels, flower can achieve up to 15% more terpene retention.

How to spot mold on cannabis

There are several ways to detect mold. In addition to professional lab testing, a visual inspection under UV light can be conducted. Signs of mold can include black, grey, white, brown or yellow spots, spores, fuzz or webbing. For consumers who may have kept their medicine in storage long-term, it’s important to do a quick mold check before consuming in case of any developments.

Signs of Moldy Cannabis:

  1. Dampness
  2. Musty, sweet, and stale odor
  3. Grey or white fuzz
  4. Specks of white powder, like white dust

Is this mold on my cannabis?

If you notice tiny white or cream-colored mushrooms on your buds, those are trichomes, not mold. Trichomes are concentrated with THC and other psychoactive cannabinoids. Boveda preserves trichomes by preventing them from drying up and breaking off while inhibiting mold growth. If there is fuzzy white stuff growing on the trichomes, that’s mold. Mold fibers are much smaller than trichomes.

How to prevent mold on cannabis

As mentioned earlier, cannabis can develop mold throughout various points of its life cycle. When the plant is drying and curing, having a well-ventilated space with plenty of fans is essential. Once the plant is dried, it’s important to keep it stored in an airtight container in a cool, dry place. Boveda’s 2-way humidity control is a great way to keep the cannabis fresh while it’s in a container.

Scientists have known for hundreds of years that a saturated salt solution is the only way to effectively add and/or remove moisture and still maintain a specific RH. Without salt, any humidity “control” only has a starting RH that changes wildly as soon as it gives up or absorbs water. A salt-water sachet is the precise and predictable way to store cannabis. Both Boveda 58% and 62% RH levels keep flower well below the moisture level that molds needs to thrive.

Moldy cannabis can be extremely dangerous – especially for medical patients with compromised immunity. Therefore, it’s vital that all medicine be tested and stored properly for protection against any and all pathogens.

By Rachelle Gordon

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About the Author

Boveda invented the world’s first 2-way humidity control in a ready-to-use packet. Inside Boveda’s semipermeable membrane contains all-natural salts and purified water.