Drying cannabis is the controlled process of slowly removing moisture from harvested plant material to prevent mold and preserve the compounds responsible for its effects and aroma. Freshly harvested flowers contain 75% to 80% moisture, which must be reduced to 8% to 12% for consumption and storage. While outdoor drying is physically possible, it is not recommended for achieving a high-quality product. This is due to the difficulty in maintaining the precise and stable environmental conditions required for a slow, even dry. The goal is a gradual process, usually taking seven to fourteen days, that allows the plant to naturally break down chlorophyll, which prevents a harsh taste.
Why Outdoor Drying is Generally Discouraged
The primary reason outdoor drying is discouraged is the inability to control environmental factors that directly impact the quality and safety of the final product. Uncontrolled fluctuations in relative humidity pose the biggest threat. Levels above 60% create an ideal breeding ground for mold and bud rot, especially during cooler nighttime hours. This mold contamination can quickly ruin an entire harvest.
Temperature extremes also rapidly degrade the plant’s valuable chemical components. If temperatures climb above 70°F (21°C), the drying rate accelerates too quickly, causing the degradation of volatile terpenes and the cannabinoid THC, which reduces both flavor and potency. Conversely, if temperatures are too low, the process slows excessively, prolonging the window for mold development. The ideal environment for a controlled dry is consistently between 60°F and 70°F (15–21°C).
Outdoor conditions introduce uncontrollable contamination sources that compromise product purity. Airborne particles such as dust, pollen, and environmental pollutants easily settle onto the sticky flowers. The drying material is also vulnerable to pests, including insects, rodents, and bird droppings. Direct exposure to sunlight, particularly UV radiation, causes the rapid breakdown of THC into the less potent cannabinoid CBN, diminishing the flower’s overall strength.
Essential Preparation for Outdoor Drying
A successful outdoor dry requires careful preparation of the plant material and the drying location to mitigate external risks. Preparation involves wet trimming, which means removing the large, non-resinous fan leaves immediately after harvest. This improves airflow around the dense buds and removes excess moisture-retaining material, which is crucial for preventing mold formation.
Location selection must prioritize protection from the elements. The drying area cannot be fully exposed to the open sky. A completely shaded, sheltered space, such as a well-ventilated barn loft, shed, or covered porch, is necessary to block direct sunlight and prevent rain or morning dew. The area should also be shielded from strong winds, which can cause the buds to dry out too quickly and unevenly.
The structural setup requires hanging the cut branches upside down. This allows moisture to exit slowly through the stem and helps the flowers retain their shape. Non-porous lines or netting should be used, ensuring adequate space between each branch. Overcrowding restricts airflow and creates pockets of stagnant, humid air, significantly increasing the risk of moisture retention and subsequent mold growth.
Managing Environmental Risks During Drying
Since the outdoor environment is unpredictable, active, ongoing monitoring and intervention are necessary throughout the drying period. Constant, gentle air movement is required to prevent stagnant air pockets where humidity accumulates. This often necessitates using small, battery-powered fans to circulate air continuously. Fans should never be pointed directly at the buds, as this can cause the outside of the flowers to dry too quickly.
Physical barriers are an important layer of protection against pests and debris. Fine mesh screening can enclose the drying area, preventing insects, rodents, and airborne contaminants like dust and pollen from reaching the plant material. The drying space must be kept meticulously clean.
The most important management technique is the continuous measurement of ambient conditions using a thermometer and a hygrometer. Relative humidity must be kept below 60%, and the temperature should not exceed 75°F (24°C) to protect the plant’s volatile compounds. If conditions drift outside these ranges, the product must be moved immediately to a controlled indoor environment to prevent degradation or mold. A daily spot check of the densest buds for visual signs of mold is also necessary.
Impact on Final Product Quality
The lack of control inherent in outdoor drying directly affects the chemical and sensory properties of the final product. Temperature swings and rapid moisture loss cause the volatilization of delicate terpenes, the aromatic compounds responsible for the flower’s unique flavor and scent profile. This loss results in a significantly reduced aroma and a blander taste compared to product dried slowly in a stable environment.
An uneven or overly fast dry also leads to a harsh consumption experience. When the drying process is rushed, chlorophyll, the green pigment in the plant, does not have enough time to naturally break down. This trapped chlorophyll results in a final product that produces a harsh smoke with a lingering grassy or hay-like flavor.
Furthermore, the potency of the flower is compromised because cannabinoids are sensitive to light and heat. Even indirect sunlight exposure contributes to the degradation of THC, which reduces the overall strength of the product. A slow, controlled dry, in contrast, preserves the cannabinoid and terpene profiles, which is necessary for a smooth, potent, and flavorful end result.