Growers can cultivate a fantastic cannabis crop, brimming with flavorful buds high in cannabinoids. However, without following the right steps to preserve those consumer-desired compounds, growers can let all that effort go to waste. Improper storage puts cannabis at risk of losing its potency, terpenes and even its safety for consumption.[1]
In this blog post, we’ll discuss why preservation and storage are the final critical steps in a successful grow operation and what growers can do to ensure their product stays in top condition until it reaches the buyer.
Importance of preservation and storage
Cannabis biosynthesizes tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA)—the carboxylic acid forms of tetrahydrocannabinol (THC) and cannabidiol (CBD), respectively. THCA and CBDA can then be decarboxylated[2] into THC and CBD through thermal processes like heating and smoking. Studies show that THCA decarboxylates into THC within an hour when heated above 100°C, and a near-linear degradation occurs when it is heated at 80°C. [3] Thus, great care must be taken to maintain THCA to avoid disappointing cannabis consumers.
Research also shows that cannabinoid and terpene concentrations significantly decrease when cannabis is dried, cured and stored. THCA and CBDA can transform into less desirable forms when exposed to light, oxygen or certain temperatures. For instance, THCA can oxidize to cannabitriolic acid[4] or isomerize[5] to Δ8-THCA, while CBDA can oxidize into cannabinodiolic acid (CBNDA) or convert into cannabielsoic acid[6] through photochemical reactions.[7]
Moreover, even if THCA decarboxylates to THC, it can further degrade to cannabinol (CBN). Time alone causes this;[8] the presence of CBN indicates that the cannabis is not fresh,[9] and “relatively large amounts” of CBN can be found in samples that have been stored for extended periods.[10]
But if cannabis is properly dried and protected from air and light, primary cannabinoids can remain active for years.[11]
Moreover, even if THCA decarboxylates to THC, it can further degrade to cannabinol (CBN). Time alone causes this;[8] the presence of CBN indicates that the cannabis is not fresh,[9] and “relatively large amounts” of CBN can be found in samples that have been stored for extended periods.[10]
But if cannabis is properly dried and protected from air and light, primary cannabinoids can remain active for years.[11]
Factors affecting preservation
How cannabis is stored plays a major role in preserving cannabinoids and terpenes. Several environmental factors influence its long-term quality and potency:
- Temperature: High temps can degrade THC concentrations. One study examined six high-potency cannabis products over four years when (1) exposed to 24 hours of light at room temperature (~72°F), (2) kept in 24-hour darkness at room temperature, (3) kept in darkness and refrigerated at 4°C (39°F) and (4) kept in darkness and frozen at -20°C (-4°F). The researchers found that products stored at room temperature experienced significant THC degradation over time, with almost no THC remaining after four years.[12]
- Humidity: Cannabis has a high moisture content at harvest—75–78% on a wet basis—making it highly perishable and prone to microbial contaminants like mold.[13] Although drying reduces moisture, humid storage conditions can still promote microbial growth.
- Light: Light exposure is the leading contributor to cannabinoid loss, especially for cannabis stored in solution.[14]
- Oxygen: CBDA oxidizes into CBNDA in the presence of oxygen, and THC oxidizes into CBN in the presence of both oxygen and light during decarboxylation.[15] One study measured THC degradation in four cannabis samples when (1) kept in a dark freezer, (2) exposed to light and air at room temperature, (3) exposed to light but sealed in plastic at room temperature and (4) exposed to air but kept in the dark at room temperature (Figure 1). Samples exposed to the air showed the greatest decrease in THC concentration, which worsened with extended storage.[16]
Excessive handling: Trichomes—tiny glands that house cannabinoids and terpenes—shield these compounds from environmental stress. Excessive bud handling can damage trichomes, leaving cannabinoids vulnerable to oxidation.[17]
Figure 1. Concentration of Δ9-THC for sealed cannabis resin samples A–D over four years under different environmental conditions: (a) in a freezer at -20oC in the dark; (b) exposed to light in a sealed plastic bag at room temperature (20–22oC); (c) exposed to light and air at room temperature (20–22oC); (d) exposed to air in darkness at room temperature (20–22oC). Image source: https://doi.org/10.1016/j.forsciint.2019.05.035
Optimal preservation and storage
Protecting cannabis’s potency and quality starts with good post-harvest care, including harvesting at the right time and trimming and drying the buds. Advanced pre-harvest techniques, such as applying hexanoic acid spray, may also be worth considering for preservation of cannabinoids and terpenes.[18]
Additionally, consider the following factors for creating optimum storage conditions:
- Packaging material: Packaging should be rigid to prevent physical damage and water permeability to avoid moisture migration. Common materials include Mylar bags, cases or tubes made of polyethylene terephthalate[19] or metal, and glass jars.[20] If the product is moving quickly to consumers, paper or cardboard containers can be used[21] with humidity control packs added to preserve freshness. Airtight jars and humidors are also ideal for maintaining consistent humidity.[22]
- Vacuum seal: Vacuum sealing stops light and oxidation from reaching the product.
- Humidity: Industry experts recommend humidity of 59‒63% to keep cannabis fresh and potent. High humidity during storage increases the risk of microbial contamination, particularly mold. Low humidity, by contrast, can make trichomes brittle. If they break off, the product loses potency and flavor. Terpenes can also degrade over time if buds become too dry.[23]
- Temperature: Dried cannabis can be stored at 18°C –20°C (64–68°F) for short periods; -20°C (-4°F) is recommended for long-term storage.[24] Research indicates that cannabis can be stored at -18°C or 4°C for around 30 weeks before THCA and THC begin to degrade.[25] However, freezing cannabis may damage the trichomes, affecting both potency and flavor.[26]
- Automated systems: Using advanced sensors to track environmental factors like temperature and humidity can help ensure optimal storage conditions.
Conclusion
Producing stellar cannabis doesn’t stop when the buds are dried. Protecting cannabis from environmental factors that degrade cannabinoids or introduce contaminants like mold and mycotoxins is crucial to running a successful grow operation that keeps customers satisfied.
Emerald Harvest Team
[1] Vujanovic, Vladimir, Darren R. Korber, Silva Vujanovic, Josko Vujanovic, and Suha Jabaji. 2020. “Scientific Prospects for Cannabis-Microbiome Research to Ensure Quality and Safety of Products.” Microorganisms 8 (2): 290. https://doi.org/10.3390/microorganisms8020290.
[2] Decarboxylation is the head-induced removal of the acidic group to become bioactive.
[3] Wang, Mei, Yan-Hong Wang, Bharathi Avula, et. al. 2016. “Decarboxylation Study of Acidic Cannabinoids: A Novel Approach Using Ultra-High Performance Supercritical Fluid Chromatogrpahy/Photodiode Array-Mass Spectrometry.” Cannabis and Cannabinoid Research 1 (1): 262–271. https://doi.org/10.1089/can.2016.0020.
[4] CBTA
[5] Isomerism is the phenomenon in which more than one compounds have the same chemical formula but different chemical structures.
[6] CBEA
[7] Birenboim, Matan, Daniel Chalupowicz, David Kenigsbuch, and Jakob A. Shimshoni. 2024. “Improved Long-Term Preservation of Cannabis Inflorescence by Utilizing Integrated Pre-Harvest Hexanoic Acid Treatment and Optimal Post-Harvest Storage Conditions.” Plants 13 (7): 992. https://doi.org/10.3390/plants13070992.
[8] Upton, Roy, Lyle Cracker, Mahmoud ElSohly, Aviva Romm, Ethan Russo, and Michelle Sexton, eds. 2014. “Cannabis Inflorescence Cannabis spp. Standards of Identity, Analysis and Quality Control.” American Herbal Pharmacopoeia.
[9] Ross, S. A., and M. A. ElSohly. 1999. “CBN and D9-THC Concentration Ratio as an Indicator of the Age of Stored Marijuana Samples.” United Nations Office on Drugs and Crime. https://www.unodc.org/unodc/en/data-and-analysis/bulletin/bulletin_1997-01-01_1_page008.html.
[10] Hazekamp, Arno. 2007. “Cannabis; Extracting the Medicine.” Leiden University Scholarly Publications. https://hdl.handle.net/1887/12297.
[11] Upton, Roy, Lyle Cracker, Mahmoud ElSohly, Aviva Romm, Ethan Russo, and Michelle Sexton, eds. 2014. “Cannabis Inflorescence Cannabis spp. Standards of Identity, Analysis and Quality Control.” American Herbal Pharmacopoeia.
[12] Fairbairn, J.W., J.A. Liebmann, and M.G. Rowan. 1976. “The Stability of Cannabis and Its Preparations On Storage.” Journal of Pharmacy and Pharmacology 28 (1): 1–7. https://doi.org/10.1111/j.2042-7158.1976.tb04014.x.
[13] Das, Pabitra Chandra, Alec Roger Vista, Lope G. Tabil, and Oon-Doo Baik. 2022. “Postharvest Operations of Cannabis and Their Effect on Cannabinoid Content: A Review.” Bioengineering 9 (8): 364. https://doi.org/10.3390/bioengineering9080364.
[14] Fairbairn, J.W., J.A. Liebmann, and M.G. Rowan. 1976. “The Stability of Cannabis and Its Preparations On Storage.” Journal of Pharmacy and Pharmacology 28 (1): 1–7. https://doi.org/10.1111/j.2042-7158.1976.tb04014.x.
[15] Wang, Mei, Yan-Hong Wang, Bharathi Avula, et. al. 2016. “Decarboxylation Study of Acidic Cannabinoids: A Novel Approach Using Ultra-High Performance Supercritical Fluid Chromatogrpahy/Photodiode Array-Mass Spectrometry.” Cannabis and Cannabinoid Research 1 (1): 262–271. https://doi.org/10.1089/can.2016.0020.
[16] Grafstrom, Karin, Kjell Andersson, Niclas Pettersson, Johanna Dalgaard, and Simon J. Dunne. 2019. “Effects of Long Term Storage on Secondary Metabolite Profiles of Cannabis Resin.” Forensic Science International 301: 331–340. https://doi.org/10.1016/j.forsciint.2019.05.035.
[17] Upton, Roy, Lyle Cracker, Mahmoud ElSohly, Aviva Romm, Ethan Russo, and Michelle Sexton, eds. 2014. “Cannabis Inflorescence Cannabis spp. Standards of Identity, Analysis and Quality Control.” American Herbal Pharmacopoeia.
[18] Birenboim, Matan, Daniel Chalupowicz, David Kenigsbuch, and Jakob A. Shimshoni. 2024. “Improved Long-Term Preservation of Cannabis Inflorescence by Utilizing Integrated Pre-Harvest Hexanoic Acid Treatment and Optimal Post-Harvest Storage Conditions.” Plants 13 (7): 992. https://doi.org/10.3390/plants13070992.
[19] PET
[20] Das, Pabitra Chandra, Alec Roger Vista, Lope G. Tabil, and Oon-Doo Baik. 2022. “Postharvest Operations of Cannabis and Their Effect on Cannabinoid Content: A Review.” Bioengineering 9 (8): 364. https://doi.org/10.3390/bioengineering9080364.
[21] Craig, David. 2023. “6 Sustainable Packaging Tips for Cannabis Growers.” Cannabis Business Times, June 12. https://www.cannabisbusinesstimes.com/departments/quick-tips/article/15687666/6-sustainable-packaging-tips-for-cannabis-growers.
[22] Bouchard, Harold. 2023. “Member Blog: The Importance of Storing Cannabis Properly.” National Cannabis Industry Association, July 5. https://thecannabisindustry.org/member-blog-the-importance-of-storing-cannabis-properly/.
[23] Ibid.
[24] Upton, Roy, Lyle Cracker, Mahmoud ElSohly, Aviva Romm, Ethan Russo, and Michelle Sexton, eds. 2014. “Cannabis Inflorescence Cannabis spp. Standards of Identity, Analysis and Quality Control.” American Herbal Pharmacopoeia.
[25] Jin, Dan, Shengxi Jin, and Jie Chen. 2019. “Cannabis Indoor Growing Conditions, Management Practices, and Post-Harvest Treatment: A Review.” American Journal of Plant Sciences 10: 925–946. https://doi.org/10.4236/ajps.2019.106067.
[26] Upton, Roy, Lyle Cracker, Mahmoud ElSohly, Aviva Romm, Ethan Russo, and Michelle Sexton, eds. 2014. “Cannabis Inflorescence Cannabis spp. Standards of Identity, Analysis and Quality Control.” American Herbal Pharmacopoeia.
