Drying and curing can make or break a harvest, and the research shows why there’s no single right answer: the conditions that best protect cannabinoids aren’t always the ones that best protect aroma, and both have to be balanced against mold.
Fast hot-air drying of hemp cut mold counts sharply without reducing total cannabinoids, but terpenes weren’t measured. Controlled-atmosphere drying chambers dried flower at least 60% faster than traditional methods, preserved terpenes and reduced the Alternaria mold that showed up in traditionally dried buds. Trimming after drying preserved the most terpenes in one chemovar.
Storage is where aroma fades. THCA fell 4–23% over four months of storage in one study, and nitrogen-flushed cans didn’t preserve total terpenes or cannabinoids any better than ordinary air over 74 days. Two reviews conclude that drying temperature, speed, method and storage conditions all shape the final product, and that standard hang-drying can produce inconsistent results.
Gaps we’re still filling: controlled studies of classic slow hang-drying conditions (temperature and humidity targets) and jar curing for drug-type flower.
Key terms
Terpenes
Aromatic compounds that give cannabis its smell and flavor. Monoterpenes (like myrcene and limonene) are lighter and more volatile than sesquiterpenes (like beta-caryophyllene).
Decarboxylation
The chemical change that turns acid cannabinoids (like THCA) into their neutral forms (like THC), driven by heat and time.
THCA and THC
Living cannabis makes THCA, an acid form. Heat and time convert it to THC. CBDA and CBD work the same way.
Studies
7 studies
Postharvest Drying and Curing Affect Cannabinoid Contents and Microbial Levels in Industrial Hemp (Cannabis sativa L.)
Plants · 2025
Hemp
Controlled experiment
Open access
Fast hot-air drying cut mold counts and didn’t reduce total cannabinoids.
Authors: Yousoon Baek, Heather Grab, Chang Chen
14(3):414
Study plant: Two cannabinoid-type hemp cultivars (‘Hempress’ and ‘Wild Bourbon’)
Freshly harvested flower from two hemp cultivars was dried three ways (hot air at 75 °C, ambient air at 25 °C, or freeze-drying) and then cured in different containers. Hot air took the flower from 77% to 6% moisture in 8 hours and cut yeast and mold counts by up to 99%. Ambient drying took a week and freeze-drying a day. Total cannabinoids didn’t change significantly with drying or curing method, though some acid cannabinoids converted to their neutral forms. The authors favored hot-air drying followed by glass-jar curing.
Improved Long-Term Preservation of Cannabis Inflorescence by Utilizing Integrated Pre-Harvest Hexanoic Acid Treatment and Optimal Post-Harvest Storage Conditions
Plants · 2024
Drug-type cannabis
Controlled experiment
Open access
THCA fell 4–23% over four months; a pre-harvest spray plus vacuum storage kept losses lowest.
Authors: Matan Birenboim, Daniel Chalupowicz, David Kenigsbuch, Jakob A. Shimshoni
13(7):992
Study plant: One high-THCA chemovar, stored for four months after harvest
A high-THCA chemovar was sprayed with hexanoic acid before harvest (or left untreated), then dried, cured and stored for four months with or without vacuum sealing. THCA fell by 4–23% during storage, with the smallest loss in plants that received both the pre-harvest spray and vacuum storage. The spray protected monoterpenes more than vacuum storage alone, and treated plants had higher levels of some cannabinoids at harvest.
In Pursuit of Optimal Quality: Cultivar-Specific Drying Approaches for Medicinal Cannabis
Plants · 2024
Drug-type cannabis
Controlled experiment
Open access
Controlled-atmosphere chambers dried at least 60% faster, kept terpenes, and reduced mold seen with traditional drying.
Authors: Matan Birenboim, Nimrod Brikenstein, Danielle Duanis-Assaf, Dalia Maurer et al.
13(7):1049
Study plant: Two medicinal chemovars (a high-THC ‘240’ and a hybrid ‘Gen12’)
Two chemovars were dried in controlled-atmosphere chambers with different gas mixes, including nitrogen-rich and low-oxygen blends, and compared with traditional drying. The chambers cut drying and curing time by at least 60% while preserving terpenes. Traditionally dried buds were heavily infested with Alternaria mold and showed some Botrytis. The best gas mix differed by chemovar and by terpene type.
Is nitrogen-modified atmosphere packaging a tool for retention of volatile terpenes and cannabinoids in stored Cannabis sativa inflorescence?
Journal of Cannabis Research · 2024
Drug-type cannabis
Controlled experiment
Open access
Nitrogen-flushed cans didn’t preserve total terpenes or cannabinoids better than ordinary air.
Authors: Luke L. MacLaughlin, Mason T. MacDonald
6:42
Study plant: Dried flower from five cultivars grown at a licensed facility, canned and stored for 74 days
Dried flower from five cultivars was canned either under nitrogen (about 4% oxygen) or ordinary air, then analyzed for 17 cannabinoids and 61 aroma compounds over 74 days. Nitrogen packaging made no significant difference to total cannabinoids or total volatile terpenes, though it shifted some individual compounds. Monoterpenes declined sharply in both treatments during storage.
Postharvest Operations of Cannabis and Their Effect on Cannabinoid Content: A Review
Bioengineering · 2022
Mixed / review
Review
Open access
Drying is the most important post-harvest step, and standard hang-drying gives inconsistent quality.
Authors: Pabitra Chandra Das, Alec Roger Vista, Lope G. Tabil, Oon-Doo Baik
9(8):364
Study plant: Review of post-harvest research on cannabis and hemp
A technical review of what happens to cannabis after harvest: how the major cannabinoids form, and how trimming, drying, curing, packaging and storage affect them. It covers drying science such as water activity and moisture equilibrium, plus newer pre-treatments like microwave heating and cold plasma. The authors note that the common hang-drying method is inefficient and can produce inconsistent quality.
Post-Harvest Operations to Generate High-Quality Medicinal Cannabis Products: A Systemic Review
Molecules · 2022
Mixed / review
Review
Open access
Drying temperature, speed, method and storage all affect what the finished flower retains.
Authors: Hebah Muhsien Sabiah AL Ubeed, Ronald B. H. Wills, Jayani Chandrapala
27(5):1719
Study plant: Literature review of drying technologies for medicinal cannabis
This review surveys traditional and modern drying technologies for medicinal cannabis and how they affect the plant’s active compounds. It concludes that drying temperature, drying rate, the drying method and storage conditions afterward all shape what the final product retains, and that the quality of the harvested material also affects drying efficiency.
Optimization of Trimming Techniques for Enhancing Cannabinoid and Terpene Content in Medical Cannabis Inflorescences
Medical Cannabis and Cannabinoids · 2024
Drug-type cannabis
Controlled experiment
Open access
A light wet trim maximized cannabinoids; trimming after drying kept the most terpenes.
Authors: Nimrod Brikenstein, Matan Birenboim, David Kenigsbuch, Jakob A. Shimshoni
7(1):111–118
Study plant: One commercial medical hybrid chemovar (Gen12)
Using a commercial hybrid chemovar (Gen12), the researchers compared trimming before versus after drying, and light versus aggressive trimming before drying, then measured cannabinoids and terpenes. A light trim before drying gave the highest cannabinoid concentrations, while trimming after drying preserved the most terpenes. All buds were dried under the same controlled conditions identified in the team’s earlier drying research.