A Guide to Drying and Curing Cannabis
The drying and curing of plants are important stages in the production of cannabis products, particularly when the intent is to utilize the plant in its flower form. Drying removes most of the moisture and curing impacts the flavor profile and effects of the bud.
When drying and curing cannabis, there are some key factors to consider, including temperature, humidity, air flow, and lighting. Even a slight deviance from optimal conditions can be detrimental to the quality of the final product.
In this guide, you’ll discover the importance of drying and curing cannabis and the main factors to consider when devising your own process.
Drying cannabis, curing cannabis
After harvest, cannabis plants are dried and then cured. Drying is often the simpler of the two processes and usually involves hanging plants in a controlled environment such that they lose most of their moisture.
Drying harvested cannabis prevents spoilage, inhibits microbial growth, extends shelf life, and allows for a pleasant consumer experience.
Curing allows for the homogenization of humidity and available moisture within dried flower batches while plants are stored in containers.
Again, strict environmental conditions must be maintained. This process can dramatically impact the flavor profile of the plants, reduce chlorophyll content, and mildly alter potency, affecting ratios of terpenes present but not overall cannabinoid content. It also affects the experience of consuming the bud and its “smokability”.
Leo Gontmakher, CEO of 4Front Ventures, explains that the curing and drying processes are essential steps that bring out the aroma and flavor of the cannabis plant. “They also prepare the cannabis flower for consumption by removing moisture and unwanted sugars that would typically cause a burning sensation in the throat,” he tells Analytical Cannabis.
Jaraud Wood, the harvest manager at Commonwealth Alternative Care, describes drying and curing as processes where a grower is able to capture all the hard work and time put into the growth of the plant. “If not dried and cured correctly, months of labor during the grow process can be erased,” he says. “The overall goal is to remove the moisture from within the flowers to promote long term storage, while maintaining a high level of secondary metabolites, or cannabinoids, terpenes, and flavonoids. These compounds are what gives the finished flower its tastes and effects.”
That said, careful drying and curing of cannabis is not always necessary due to product type. Nick Tennant, founder and CTO of Precision Extraction, explains that around fifty percent of products sold at dispensaries are extracts. The consideration for drying and curing cannabis used to make these products will be different from those used for raw plant products.
For example, plants used to produce live resin products might be rapidly freeze-dried immediately after harvest. In many other extraction processes, plants will be exposed to high temperatures, high pressures, and/or solvents, so terpenes and other heat-sensitive molecules from the original harvested plant material will be re-added or replaced in the final product. You also don’t have to worry about bud structure and chlorophyll content, among other factors. Tennant notes that you can often be far more liberal with the heat and timing in these cases.
With the above in mind, the sections below will focus on processes for plants that are to be consumed as flower (bud) rather than extracts.
How to dry cannabis
The drying process begins immediately after harvest and it’s important to ensure that it’s done right. As Graham Farrar, chief cannabis officer of Glass House Farms, explains.
“Each strain will require a different approach to dry properly, but getting the plant stable in the first 24 hours by removing as much water as possible is critical,” he tells Analytical Cannabis. “After 24 hours, you can back off and let the plant ease into a slower dry cycle, optimally finishing around the 10-day mark.”
The setup you use to dry the plant will depend on the trimming process you use:
- Dry trimming: If you’re trimming plants after they’ve been dried, then you’ll be able to hang them from a line or hanger. Hanging is preferable as it prevents buds from becoming misshapen and buds tend to dry more evenly. To test if plants are ready for trimming, you can try bending a branch. If it bends, it needs more drying. If it snaps, it is ready for trimming and curing. Another method includes use of a water activity meter to determine readiness for cure. If the water activity is below 0.6-0.65 Aw, the product is safely dried enough to move on to the curing process. A moisture meter can also be used, with flower buds typically less than 13 percent moisture being ready for cure.
- Wet trimming: If you trim the plants before drying, then you’ll have smaller plant parts to dry and will need to use a rack. You can check when buds are ready for curing by squeezing them. If they still feel wet or moist, they likely need more time before moving on to curing. A water activity meter or moisture analyzer can also be used here.
As noted by Wood, the main factors to consider when drying are the desired strain qualities and environmentals: temperature, humidity, air flow, and lighting. These parameters are not exact but vary within acceptable ranges due to the high variability of cultivation and storage environments across the industry. Ideally you follow a science-based approach of reducing available moisture early in the drying process, within the first 2-3 days, then slowly dropping moisture content over 1-2 weeks to an acceptable level, as determined by state regulations.
Dry trimming in action.
Cannabis drying temperature
Temperature is key and you need to find a balance. “Yes, it must be warm enough for the product to lose its moisture. However, product degradation can begin as low as 68 degrees Fahrenheit,” explains Wood. Drying temperatures can range from 55-74 degrees Fahrenheit. The goal is to dry slowly enough to not volatilize terpenes or over dry the product.
One example he provides is the terpene myrcene (also found in mangos). “This begins to volatilize at low temperatures, so in order to maintain aromas and flavors, we must keep the temperature of the drying space low.”
The humidity needed for drying cannabis
“Humidity must be carefully monitored, mainly in order to prevent any mold from growing on the plant. With that said, we also don't want to over-dry the product where it crumbles to dust,” says Wood. Typically, relative humidity levels between 40-60 percent are desired for drying harvested cannabis flower.
Air movement is important too. Wood explains that while the plants are hanging, there is a need for constant filtered, fresh air movement. This air movement should be subtle and not directly blowing on the plants. Take care to check filters, dehumidifiers, fans, and air purification systems often for the presence of mold or bacteria. Exposing drying plant material to contaminated or dirty air can cause product to fail required safety testing.
And we shouldn’t forget about lighting. “Light will cause the oils of the plants to rapidly degrade, so this is unwanted during this process,” notes Wood.
How long to dry cannabis
“Drying the cannabis plant, on average, will take about 7–10 days depending on the strain,” Gontmakher says. Every cannabis strain requires a specific amount of cure and dry time, though, which can differ slightly by environmental conditions.
As for conditions, Tennant suggests 50–60 percent humidity at 55–65 degrees Fahrenheit. This should help you remove about 80 percent of the moisture. Tennant reiterates the importance of darkness, as light can degrade terpenes and cannabinoids.
How to cure cannabis
Once the initial drying stage is complete, curing can begin. This is often described as an artisanal process. Indeed, Tennant likens it to dealing with fine wines. “They’re all aged a little bit differently. Everybody has their process.”
Farrar notes the importance of fine-tuning your setup. “While it is true that you can’t fix a poorly grown plant in cure, you can certainly ruin a properly grown one, so it’s important to get it right.”
Once trimmed, plants are usually loosely packed in glass vessels. For small batches, these could be wide-mouth mason jars; in large-scale production, glass-lined vessels may be used. Again, since this is an artisanal process, there is no one size fits all. Some producers prefer to avoid airtight vessels and instead opt to cure plants in porous containers, such as paper bags or wooden boxes. It is common for large-scale operations to use 5-10-gal plastic buckets with screw top lids or curing tubes with or without container liners.
Curing flower
The curing process usually takes a little longer than drying, with the plants being stored in a dark, controlled environment between 40-50 percent humidity and a temperature below 70 degrees for a week or several months. The material must be checked for mold and other contamination, particularly in the early stages - the curing vessel must also be opened at regular intervals.
Cured cannabis flower.
As Farrar explains, “you need to allow additional time for the moisture to rebalance and spread throughout the bud evenly.” Curing is not a “set it and forget it” process, and plants need to be checked regularly. Vessels are typically “burped” at regular intervals, whereby they are opened to let gases (ethylene, CO2, etc.) escape and oxygen enter.
If there is any sign of mold, the jars should be left open for a few hours. An ammonia smell indicates the presence of anaerobic bacteria and is another sign of too much moisture, again requiring vessels to be left open for several hours or longer. Product can also be exposed to UV-C light or irradiation to halt microbial growth. Checks can usually be made less frequently as curing progresses.
Conclusion
Overall, the resounding advice when curing and drying cannabis is to follow the “low and slow” and approach. Tennant’s top tip is “Be patient, never try to rush it.” And Wood agrees, explaining that low temperatures promote higher levels of secondary metabolites, and the longer you can cure your product, the cleaner, smoother, and more flavorful your cannabis will be.
*Update: This article was updated on May 26, 2022, to include new insights from its reviewer, Lydia Abernethy.
