Drying cannabis after harvest removes moisture to preserve the chemical compounds within the flower. While technically possible, drying your harvest outdoors is strongly discouraged by experts. The uncontrolled external environment introduces significant risks that compromise the quality, safety, and potency of the final product. Maintaining the delicate balance required for a successful dry is almost impossible when exposed to unpredictable elements.
Required Environmental Conditions for Drying Cannabis Outdoors
A high-quality dried product requires a slow, controlled process lasting seven to fourteen days. Ideal conditions involve a narrow temperature range of 60–70°F (15–21°C). Maintaining temperatures below 70°F prevents the premature evaporation of volatile compounds that contribute to flavor and aroma.
Relative humidity (RH) must also be carefully regulated, ideally hovering between 45% and 55% during drying. If the RH drops below 40%, the buds dry too quickly, resulting in a brittle product with a harsh smoke. Conversely, humidity levels exceeding 60% drastically increase the risk of mold and mildew proliferation.
The primary challenge of outdoor drying is the inability to maintain these metrics consistently. Natural fluctuations in temperature and sudden weather shifts, like rain or fog, make the environment unstable. This instability compromises the slow, even moisture removal needed before the final curing process.
Primary Hazards of Outdoor Exposure
The most significant threats to cannabis dried outdoors are biological, primarily mold and mildew, which thrive in uncontrolled high-humidity conditions. Morning dew or unexpected rainfall can quickly saturate the dense flower structure, creating an immediate breeding ground for destructive fungi like Botrytis cinerea (bud rot). Once this mold takes hold, it rapidly ruins large portions of the harvest, making the material unsafe for consumption.
Pests also pose a major contamination risk, as they are naturally attracted to the drying plant material. Insects like spider mites, aphids, thrips, and fungus gnats may have been present on the plant before harvest and can remain on the buds as they dry. Others, such as corn earworms, can tunnel into the dense flower structure, leaving behind waste that causes contamination.
The physical elements introduce additional hazards beyond biological contaminants. Uncontrolled wind exposure causes the buds to dry rapidly and unevenly, leading to a brittle exterior that traps moisture inside the core. Furthermore, drying outdoors exposes the harvest to fine particles like dust, pollen, and airborne debris, which adhere to the sticky trichomes and degrade the cleanliness of the final product.
Mitigation Strategies for Outdoor Drying
If an indoor environment is unavailable, the first step in mitigating outdoor risks is to create a sheltered microclimate. Drying should never occur in direct sunlight, which degrades cannabinoids and terpenes, so a completely dark or deeply shaded area is mandatory. Enclosed spaces like carports, sheds, or covered porches that block direct rain and sun exposure are better alternatives than open air.
Within this sheltered space, growers must ensure gentle and constant airflow to prevent stagnant, moisture-laden air pockets. Oscillating fans can circulate air, but they should never be pointed directly at the buds, as this causes rapid, uneven drying. Physical barriers are also important for keeping pests and debris away from the delicate flowers.
Hanging the harvest inside a fine-mesh screen enclosure or a netted drying rack acts as a barrier against flying insects and falling debris. This protection requires constant vigilance, including hourly monitoring of environmental conditions using a thermometer and hygrometer. If temperatures spike above 70°F or humidity exceeds 60%, the harvest should be immediately moved to a more stable location.
Impact on Final Product Quality
Even if mold and pests are avoided, the lack of control in an outdoor environment directly affects the chemical quality of the finished product. A proper dry reduces moisture slowly, allowing enzymes to break down chlorophyll and other compounds that contribute to a harsh taste. Rapid drying, caused by high outdoor temperatures or excessive wind, prevents this breakdown, resulting in a product that smokes harshly and tastes grassy.
The most significant loss is the degradation of terpenes, the aromatic compounds responsible for the flower’s flavor and scent profile. Terpenes are highly volatile, and exposure to temperatures above 75°F causes them to evaporate prematurely. This loss results in a less flavorful final product with a diminished aroma, reducing the synergistic effect between cannabinoids and terpenes.
Furthermore, direct exposure to light, especially ultraviolet (UV) light, accelerates the degradation of cannabinoids during drying. This process reduces the flower’s potency, as compounds like THC break down into less desirable cannabinoids. Therefore, even a successful outdoor dry that avoids contamination will likely yield a product that is less potent and satisfying than one dried under controlled, dark conditions.