Marijuana, like any dried plant material, is susceptible to colonization by fungi if not handled and stored correctly. Mold occurs when fungal spores, which are nearly everywhere, find an organic food source and suitable environmental conditions. Understanding how contamination occurs and how to detect it is paramount for preserving the quality and safety of the consumer.
Conditions That Cause Mold Growth
Mold proliferation on dried cannabis flowers is tied to environmental factors. The greatest factor contributing to fungal development is high relative humidity (RH), especially levels consistently above 65%. When the surrounding air contains too much moisture, the flower material absorbs it, creating an ideal damp environment for spores to germinate. Warm temperatures, typically above 77°F, also accelerate the growth rate of mold. Poor airflow, either during curing or within a storage container, allows humid air pockets to form, encouraging fungal development.
Identifying Moldy Marijuana
Detecting contamination requires a careful sensory inspection, as mold can sometimes be mistaken for the plant’s natural features. Visually, mold often appears as fuzzy or powdery patches, usually in shades of white, gray, or blue-green. This fuzzy growth may look like fine cotton strands or a spiderweb, often deep inside the bud where moisture is trapped.
It is important to differentiate mold from trichomes, which are the desirable, stalked glands covering healthy cannabis that appear crystalline or sparkling. Mold, such as powdery mildew, tends to have a dull, dusty, or chalky texture, lacking the shiny, crystalline structure of trichomes. An off-putting odor is another strong indicator, as moldy cannabis typically smells musty, mildewy, or like damp clothes or a basement. Severe mold contamination can produce an ammonia-like or stale, sweat-like odor, distinctly different from the normal pungent aroma of cannabis. When touched, a moldy flower may feel excessively damp, mushy, or spongy instead of being firm and slightly sticky. If any of these visual, olfactory, or textural red flags are present, the product should be disposed of immediately.
Health Risks of Consuming Mold
Consuming moldy cannabis, particularly through inhalation, introduces fungal spores directly into the respiratory system, which poses several health hazards. Exposure can trigger allergic reactions, leading to symptoms like coughing, wheezing, and chest pain, and may exacerbate pre-existing conditions like asthma. The inhalation of mold spores can lead to respiratory infections and long-term lung irritation, even if the mold is not immediately visible.
A significant risk comes from molds like Aspergillus, which commonly grows on agricultural products and can cause a serious fungal infection called aspergillosis. While healthy individuals may not be severely affected, those with compromised immune systems are highly susceptible to invasive pulmonary aspergillosis, which can be life-threatening. Certain fungi also produce toxic compounds called mycotoxins, which are known human toxins and carcinogens. Mycotoxins can survive the heat of combustion and remain hazardous, potentially causing systemic health issues beyond the lungs. Since no method can reliably remove all mold spores or mycotoxins once contamination has occurred, the safest action is to discard the entire contaminated product.
Storage Techniques to Prevent Mold
Preventing mold growth relies on controlling the environment where the cannabis is stored. The best practice is to use airtight, non-porous containers, with glass jars being an ideal choice, to shield the flower from outside humidity. Storing the containers in a cool, dark location, ideally between 60°F and 70°F, helps preserve cannabinoids and terpenes while discouraging fungal growth. Humidity control packs are highly effective tools for maintaining a stable environment inside the container, keeping the relative humidity in the optimal range of 55% to 62%. It is advisable to avoid refrigeration or freezing, as removing the product from the cold can cause condensation to form on the buds, introducing moisture that encourages mold development.