3 principles of safe drying: How to prevent your harvest from molding

After the harvest you are not done yet. It is during drying that it is decided whether your yield will turn into a fragrant, high-quality dried product — or end up in the trash because of mold. Mold can appear quickly and can ruin the entire harvest within a few days. How to recognize mold, why it develops and how to prevent it? Follow these three principles.

Molds are among the most common and at the same time most dangerous threats during the drying of herbs. At first glance they may appear as an inconspicuous white coating or small gray spots, but in reality they are microscopic fungi that spread rapidly and can spoil the entire harvest. They most often appear inside dense flowers, where moisture accumulates and sufficient air flow is lacking. Their development is promoted primarily by high humidity, inadequate ventilation and careless hygiene when handling harvested plants.

Choose the right drying method

If you want your herbs to retain as many aromatic terpenes as possible and not lose their active compounds, make sure they dry slowly. Fast drying does reduce the risk of mold, but at the cost of the quality of the dried product. Quickly dried herbs have an unpleasant aroma and taste bitter.

The optimal drying time is roughly 7 to 21 days and will depend on temperature, humidity and movement of the surrounding air, as well as on the size of the plants and their flowers. If you dry whole plants (hung upside down by the crown), they will dry the slowest. Drying will speed up somewhat if you divide the plants into individual branches. The fastest is drying on nets, where you can dry individual flowers separated into smaller parts. A new method is drying in drying bags made of breathable plastic. These protect the flowers from mold spores while locking in valuable terpenes inside.

The drying speed is also affected by how you clean the plants before drying. If you only remove the large leaves and trim the small “petal” leaves on the flowers after drying (dry trim), they will dry a bit more slowly. If you thoroughly trim the flowers before drying (wet trim), they will dry faster.

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Don't underestimate the right climate

Molds thrive best in a humid environment. During the drying process the relative humidity should not exceed 65%. Ideally you should keep humidity in the range of 50% to 55%. You can easily reduce the humidity in the drying room with a dehumidifier, but be careful that the warm air from the device does not blow directly on the flowers. They would dry too quickly.

The ideal temperature for drying medicinal herbs is about 18 °- 20 °C. At higher temperatures valuable monoterpenes evaporate quickly. If you want to slow the drying a little, you can lower the temperature to 16 °C. Remember, however, that slower drying increases the risk of mold infestation of the yield.

To prevent moisture condensation, ensure continuous air circulation in the drying room. If you are drying in a grow tent, keep the exhaust fan on at least at a low setting — it will help remove humid air and bring fresh air in. In the room where the tent is located, open a window or at least a door to the adjacent room so air can move freely and not accumulate in a closed space. If conditions allow, you can also use a small fan to gently move the air among the drying flowers. Be careful, though, that the airflow does not point directly at them.

Carefulness pays off

Be extremely thorough during harvest, drying and subsequent processing. It would be a shame to throw away months of hard work in the final stage. During harvest carefully inspect the plants for signs of mold. Pay special attention to the largest flowers, which may appear healthy on the outside but be moldy inside. If you encounter a moldy part of a plant, promptly separate it from the rest of the yield and be extra cautious during drying. Often in such cases it is better to split large flowers into smaller parts and dry them on nets.

Also observe hygiene. Disinfect scissors and other tools before use and use disposable gloves. This will protect not only the plants but also your hands from resin, which can be irritating. If you have dealt with moldy parts, disinfect the tools again after removing them and change your gloves for a new pair.

Monitor the humidity and temperature in the drying room with a thermometer with a hygrometer and check every day that everything is proceeding smoothly. Mold can appear on the flowers even during the drying process. In that case, promptly remove the affected parts, lower the humidity and raise the temperature in the dryer.

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