Cannabis can grow mold if not handled, dried, cured, or stored properly. This common issue arises from specific environmental factors that encourage fungal development. Understanding how to identify, why it forms, and how to prevent it is important for maintaining the quality and safety of cannabis.
Identifying Mold on Cannabis
Recognizing mold on cannabis involves both visual inspection and scent detection. Visually, mold often appears as a grayish-white powdery or fuzzy coating, differing significantly from the crystalline appearance of healthy trichomes. It can also manifest as dark spots, discoloration such as brown, black, gray, or yellow patches, or even cobweb-like structures. Trichomes, which are beneficial, are typically shiny, sticky, and crystal-like with stalked, bulbous heads, whereas mold looks dull, fuzzy, or web-like.
Beyond appearance, moldy cannabis often emits a distinct, unpleasant odor. This can range from a musty, mildewy, or damp smell, similar to an old basement or wet cardboard, to an ammonia-like or even sweat-like scent. Healthy cannabis, conversely, possesses a fresh, often earthy, pine, or citrus aroma. If the cannabis feels unusually wet, mushy, slimy, or leaves a chalky residue, these textural changes can also indicate mold.
Why Mold Grows on Cannabis
Mold growth on cannabis is primarily driven by specific environmental conditions that favor fungal proliferation. High humidity and warm temperatures create an ideal breeding ground for mold spores. If the relative humidity (RH) consistently exceeds 60-65%, the risk of mold developing significantly increases.
Lack of adequate airflow is another major factor, as stagnant air traps moisture and allows spores to settle and multiply. Improper drying or curing of cannabis after harvest leaves residual moisture within the plant material, making it highly susceptible to mold, even if stored correctly afterward. Storing cannabis in containers that are not airtight or in environments with fluctuating temperatures can also lead to condensation, contributing to moisture buildup. Exposure to mold spores from the environment, other infected plants, or unclean equipment can introduce contamination at any point in the supply chain.
Health Concerns from Moldy Cannabis
Consuming or inhaling moldy cannabis can pose several health risks, particularly due to the presence of mycotoxins. Mycotoxins are toxic compounds produced by certain molds, such as Aspergillus and Penicillium, which can contaminate cannabis. Ingesting these mycotoxins can lead to various adverse effects, including gastrointestinal issues like nausea and vomiting, and in more severe cases, liver or kidney damage.
Inhaling mold spores, whether through smoking or vaping, can irritate the respiratory system. This may result in symptoms such as coughing, wheezing, and shortness of breath, and can exacerbate existing conditions like asthma or allergies. Individuals sensitive to mold may experience allergic reactions, including sneezing, nasal congestion, itchy eyes, and skin rashes.
The risks are considerably higher for individuals with weakened immune systems or pre-existing lung conditions. For these populations, inhaling mold from cannabis can lead to severe infections in the lungs and other organs, including conditions like aspergillosis, which can be life-threatening.
Preventing Mold Growth and Proper Storage
Preventing mold growth on cannabis largely depends on meticulous drying, curing, and storage practices. Immediately after harvest, proper drying is crucial, ideally in a controlled environment with temperatures between 60-70°F (15-21°C) and relative humidity around 50-60%. Ensuring good airflow during this phase helps prevent moisture pockets that encourage mold.
Following drying, the curing process further reduces moisture and enhances quality while deterring mold. This involves storing buds in airtight containers, such as glass jars, and “burping” them regularly by opening the lids to release excess moisture and allow fresh air exchange. During curing, maintaining a relative humidity of 58-62% inside the containers is recommended.
For optimal long-term storage, cannabis should be kept in airtight glass jars in a cool, dark place, away from direct sunlight and heat, which can degrade cannabinoids and terpenes while fostering mold. Humidity control packs, such as those designed to maintain 58-62% RH, can be placed inside storage containers to regulate moisture levels effectively. Additionally, maintaining cleanliness in handling and using clean equipment minimizes the introduction of mold spores.