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What Influences Degradation of THC and Other Cannabinoids?

December 8, 2016
Cannabis is perishable, meaning that at some point your prized bag of fresh flowers is going to punch out its time card and expire. What was once a vibrant green, fresh-smelling sack of cannabis buds will eventually all but lose those pungent aromas as well as that vibrant hue. Furthermore, your fluffy buds will at some point crisp up and dry out, leaving you with a pretty dismal product. Such is the nature of degradation, and your cannabis must play by the same rules as any other harvested crop.

Fortunately, the factors that influence the degradation of cured cannabis flowers are easy to understand and relatively simple to control.

Cannabis Freshness is Limited After It’s Harvested

Scissors Trimming Mature Indoor Marijuana Bud for Harvest

As soon as a cannabis plant has been harvested, it begins to degrade. Not only is the plant itself no longer alive and receiving nutrients from the root ball it was once attached to, the cannabinoid biosynthetic pathways have been disrupted as well. In this process, cannabinoids and terpenes synthesize into other compounds, subsequently altering their psychoactive properties. For example, temperature has the ability to cause THCA to decarboxylate and become THC (which is highly psychoactive), but heat and light can cause THC to degrade to CBN over time as well.


What is decarboxylation, and why does your cannabis need it?

Once a cannabis plant has been harvested, dried, and cured, its optimal freshness zone becomes a finite window that can be extended only by carefully controlling various elements that include not only temperature and relative humidity, but also UV exposure and ambient oxygen levels.

How Temperature Impacts Cannabis Degradation

Modern furnace setting panel. Depth of field on the buttons

Temperature can affect the degradation of cannabis in several ways. Ideally, cannabis should be stored at temperatures not to exceed 70F degrees. Any higher and this begins to introduce an environment conducive to bacterial and mold growth within your flowers.

Furthermore, volatile monoterpenes begin to polymerize at surprisingly low temperatures, meaning that the flavor and aromatic profile of your cannabis flowers could change as well. When exposed to prolonged high temperatures, cannabinoids begin to decarboxylate and/or degrade. THCA will first lose its carboxyl ring in this process, converting it to THC, which can eventually degrade to CBN through prolonged exposure to elevated temperatures.


What Is CBN (Cannabinol) & What Are the Benefits of This Cannabinoid?

Conversely, cannabis kept too cold, in a freezer for instance, can risk elevating levels of relative humidity, which can force moisture to the surface of a plant and thus break down trichomes in the process.

How Humidity Impacts Cannabis Degradation

Vapor from humidifier in the morning light

High relative humidity in and of itself can affect cannabis degradation by introducing high levels of moisture back into the flowers. Harvested cannabis experiences a rapid slowing of fluid transfer during the drying and curing phase. Optimally, cannabis should be stored with a relative humidity in the 59-63% range to avoid adverse degradation in either direction.

With the reintroduction of high amounts of moisture, cannabis flowers not only risk mold but can also bring along ammoniated flavors due to the restricted air circulation. On the other end, low humidity can negatively impact cannabis degradation by drying leaves and foliage out, causing them to become brittle and fragile.

How UV Light and Oxygen Impact Cannabis Degradation

Blue sky.

Where temperature and humidity are both highly influential to cannabis degradation, high exposure to UV light and oxygen can perhaps cause the highest rates of degradation in the shortest time frame. UV rays can break down organic matter at a rapid rate, causing cannabinoid degradation and loss to occur. This process can only be slowed by limiting light exposure to cured flowers.

Elevated exposure to oxygen can also cause rapid cannabinoid degradation. THC, when left in highly oxidized environments, will convert more rapidly to CBN, which is why it’s important to control both oxygen levels and RH when curing cannabis buds.


What is THC (Tetrahydrocannabinol)?

To summarize, temperature, humidity, airflow, and light are the four major factors that influence the degradation of cannabis. All four variables represent a spectrum that harvested cannabis flowers teeter on. Controlling these variables and maintaining their proper levels can significantly prolong the shelf life of your cannabis flowers by limiting exposure to the processes that influence the degradation of not only the floral clusters themselves, but the cannabinoids and terpenoids contained within them.

Although cannabinoid degradation is an inevitability and your cannabis will eventually expire, maintaining a highly controlled environment is the best way to combat the natural processes that will render your stash undesirable, leaving you with fresh flowers for longer than you may have previously anticipated.

Patrick Bennett's Bio Image

Patrick Bennett

Patrick lives with his wife and daughter in Denver, where he spends his time writing, photographing, and creating content for the cannabis community.

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  • Franklin

    What is the problem with THC degrading to CBN? Many patients who enjoyed the famous red and gold 1970’s strains prefer a well cured flower to a fresh cut. CBN is also psychoactive and reduces inflammation. It could be argued that CBN is a time release delivery of the same effect.

    Take a vapor dab. There is a rush following that, but the total effect is not long lasting. Pure THC alone doesn’t seem to have a long lasting effect on many people. For medical use of pain management, eating an natural plant infused product delivers the longest lasting relief but inhaling the natural smoke of flowers can offer relief for hour where I don’t find that in high THC dabs and vape preparations.

    Many people buy fresh flowers at the dispensary and store favorite strains in the small bell jars for up to a year. Green will turn brown, orange and darken over that period but there is still medical benefit there. My own preference is flowers that are stored jar for about a month to reach prime. That’s stored in a capped Bell jar in something similar to a wine cellar. I do taste the fresh strains and some of them seem ready right from the dispensary. All the top 10 strains are already well cured it seems. But, a friend of mine found a bottle of the first batch of Blue Dream that was probably two years old. He said it was browned but no ammonia smell or sign of mold. The effect was reported as good.

    This is a very good article and it helps to explain some of the confusion with older medical marijuana patients. Those who recall the great strains of the past have a hard time accepting the high THC tests of the new strains. The reality it that “Woodstock Weed”, as the prohibitionist like to call it, was just not very fresh material and had never been stored in the proper containers or environment. This is just a theory, but I believe those strains would have tested high in CBN, even though low in THCA. Not as high as temperature controlled indoor growing but still high THC strains when they were fresh. Anything coming from Mexico or South America or Jamaica was not fresh.

    To put it into perspective people need to remember that there was no UPS, or FedEx back then. Nothing moved at the speed of business. Most of the cannabis in the past was grown outdoors in one of the border countries or islands. Transported by trucks and stored in old warehouses. Occasionally we would get fresher greener strains, and sometime fully female flowers, but only at harvest time of year. The rest of the commercial brown cannabis was already months or years old maybe. A “lid” of cannabis was nearly always brown, gold, or reddish brown. Aside from October to December.

  • lovingc

    Glass is the best to keep it fresh,and brown glass or better a light free environment.

  • Mick Thorn

    Vacuum seal in a brown glass jar and keep in a dark cool environment. Always reseal if you are dipping from the jar.

  • mahabhangara

    Is this all the same when considering various forms of concentrate?

  • Francis

    It would be nice if references were included.

  • Buddah Chambless

    Here’s the problem we’re all having, we are told that at 325° thca turns into thc but beyond that nobody can get a definitive answer. Does simply heating up the wax in your puck with a lighter turn it into thc and your wax go to bad in a week or what? Do you take a dab out once its been heated and try 3dab and nothing happen? Come on I’m a connoisseur of the plant and use it in many ways but I fully understand the importance of the question. The cannabis plant has been medically legalized in the u.s. for around 40 years and we still can’t get an answer.