Mold is one of the biggest threats to cannabis growers, especially during the drying and curing process. Mold can ruin your harvest, pose health risks to users, and drastically reduce the quality of your buds. In this post, we’ll explore the types of mold that affect cannabis, how they develop, and the steps you can take to prevent mold from damaging your crop.

Types of Mold in Cannabis

1. Botrytis (Bud Rot):

• What it is: A grayish mold that attacks the buds from the inside out, making it difficult to detect until the damage is severe.

• Where it develops: In dense, moist environments inside the bud where air circulation is poor.

2. Powdery Mildew:

• What it is: A white, powdery fungus that spreads across leaves and buds, creating a dust-like coating.

• Where it develops: On the surface of leaves and buds, especially in conditions of high humidity and poor airflow.

3. Aspergillus:

• What it is: A type of mold that can release dangerous mycotoxins, harmful to inhale, particularly for people with compromised immune systems.

• Where it develops: In overly damp environments, particularly during the drying or curing phase.

How Mold Develops

Mold thrives in specific environmental conditions, and preventing it requires controlling these factors:

• High Humidity: Cannabis that is exposed to a humidity level above 60% during drying or curing is at risk of developing mold.

• Poor Air Circulation: Stagnant air allows moisture to build up, creating the perfect environment for mold spores to grow.

• Excessive Moisture in Buds: If buds are not dried properly and retain too much moisture, mold can start developing deep within the dense flower.

• Temperature: Mold tends to thrive in warm conditions, typically between 70–85°F (21–29°C). If your drying or curing environment is too warm, you risk mold contamination.

How to Prevent Mold

Preventing mold comes down to controlling your growing, drying, and curing environments.

1. Control Humidity Levels

• During growing, keep humidity between 40–50% during the flowering stage to prevent mold from developing inside the buds.

• During drying, maintain a humidity level between 45–55%. Using a hygrometer to monitor humidity will help you keep things in check.

• During curing, keep the humidity inside the jars at 60–65% by using humidity control packs to ensure your buds don’t get too moist.

2. Improve Airflow

• Use oscillating fans in your grow room to keep air moving around the plants.

• When drying, ensure proper air circulation by hanging plants with enough space between them, and avoid crowding the drying room.

• When curing, don’t pack the jars too tightly with buds. Leave some space for air to move around, and “burp” the jars by opening them daily for the first week to release any trapped moisture.

3. Keep Temperatures in Check

• Aim to keep the temperature between 60–70°F (15–21°C) during drying. Anything above this could promote mold growth.

• When curing, a cool and dark place is ideal. Store your jars at around 60–65°F (15–18°C) to prevent heat from encouraging mold.

4. Inspect Buds Regularly

• Check for signs of mold, particularly bud rot, which can start deep inside the flower. If you notice any signs of mold, remove and discard the affected buds immediately to prevent it from spreading.

• During curing, inspect the buds every time you burp the jars, looking for any unusual smells or appearances, such as a musty odor or fuzzy growth.

Dealing with Mold-Infested Buds

If you find mold, you should discard the affected buds. Smoking or consuming moldy cannabis can cause serious health issues, especially respiratory problems or allergic reactions. Even if only a portion of the crop is affected, it’s safer to remove the bad buds to protect the rest of your harvest.

Conclusion

Mold can quickly ruin a harvest, but with the right environmental control and regular monitoring, you can significantly reduce the risk. Always prioritize keeping your drying and curing spaces clean, cool, and properly ventilated. By keeping humidity, airflow, and temperature in check, you’ll ensure a mold-free, high-quality harvest.

Pro Tip: Investing in a dehumidifier or humidity packs can be a game-changer for keeping your drying and curing space within the ideal range!