Degrading THC, like lowering the active ingredient of your plants

High thc cannabis plant

Like all good things, the presence of the active ingredient cannabis will tend to decrease over time, thc (delta-9-tetrahydrocannabinol) is a perishable compound and factors such as light, air, temperature and humidity contribute to its slow but unstoppable decline.

You’ve most likely heard that storing cannabis at its best requires a cool, dark place. We’ll get closer to the reason behind it in a moment, but overall, this is a fair idea when it comes to protecting the integrity of the cannabinoid content of cannabis plants.

Regardless of the level of storage, THC levels will eventually drop. A 1999 study found that tetrahydrocannabinol levels decreased over time while CBN levels increased in properly stored cannabis plants. The study placed dried plant material in closed barrels contained in a ventilated dark vault.

Temperatures were relatively stable, ranging between 20 and 22 degrees Celsius. To measure the rate of degradation, the researchers collected samples from the barrels each year over the course of four years.


A cannabis plant begins to degrade as soon as it is harvested. Not only is the plant itself no longer alive and receiving nutrients from the root ball it was attached to, but the biosynthetic pathways of cannabinoids are also disrupted. In this process, cannabinoids and terpenes synthesize into other compounds, subsequently altering their psychoactive properties.

Impact of Environmental Factors


The high relative humidity in the grow room itself can affect the degradation of cannabis by introducing high levels of humidity into the flowers.

Ideally, cannabis should be stored at a relative humidity of 55-65% to avoid negative degradation and consequent loss of its active ingredient. Furthermore, the flowers with the introduction of high levels of humidity in the grow room risk bringing with them flavors of ammonia due to the restricted air circulation. On the other hand, with low humidity levels, the flowers can become too fragile.

Lower humidity of the grow box.

A good step to prevent it from degrading and to keep the humidity of the grow room low during flowering. To obtain the right level of ideal humidity in your grow box, it will be necessary first of all not to exceed with watering, and above all not to give water to the plant when the lights are off; because that will cause the humidity levels in your own grow room; and this could pose a serious problem to both the health of our marijuana seedling and the final crop.

If, despite all due attention, the humidity levels continue to be above normal, it will be necessary to install a air extractor. Cannabis will need somewhat higher humidity levels during the growing phase; subsequently, ending the growth phase and entering the flowering phase it will be necessary to lower them. Anche utilizzando un abbattitore di temperatura professionale può essere utile in questa fase.

To accurately measure the humidity levels present in the air of the cultivation environment, it may be necessary to use a digital thermo-hygrometer.

THC CBD degradation in water-soluble form

UV Light and Oxygen:

High exposure to UV rays and oxygen can cause the highest rate of degradation in the shortest possible time.

If THC is left in highly oxidized environments it will convert to CBN more quickly, so it is important to control both oxygen and relative humidity levels when treating cannabis buds.

The results…

The study found that, after a year, the tetrahydrocannabinol content decreased from its original amount, starting from an average level of 16.6% thc. Checking the sample two years later, thc decreased from its initial amount by an average of 26.8%. Finally after three years, it decreased from its initial amount by an average of 34.5%. After four years, it decreased from its initial amount by an average of 41.4%.

These percentage changes suggest that THC degradation is more extreme in the first year, but reduces to an annual decline of around 7% in subsequent years. The results seemed to imply that high levels of tetrahydrocannabinol exhibited a faster degradation rate: the more THC in the cannabis sample, the more rapidly it degraded in the first two years.

Of course, there is no universal degradation rate since every cannabis strain, flower and storage environment is different. some flowers can last much longer than others. this is especially true if the storage environment is cold, dark and dry (not arid).

Let’s do it… The 3 Fastest Ways to Lower Your Cannabis THC Level

If you want to protect the integrity of the tetrahydrocannabinol content in your cannabis product for as long as possible, don’t follow these steps. but if your harvest has a few percentage points above the legal level (0.6% in Italy, 1% in Switzerland) and your harvest is slightly higher using this method you can lower the levels of active ingredient so as to allow you a marketing within the parameters of the law.

Place it in direct sunlight.

As with temperature, light instigates a biosynthetic process in a cannabis plant which results in the deterioration of its cannabinoid levels. Since 1971, the scientific community has been aware of the effects of light on the degradation of THC. A study published that year concluded that the best storage method for cannabis was under nitrogen and in the dark.

A few years later, in 1976, research examining cannabinoid stability over the course of two years found that light exposure was the most effective “variable” for depleting all cannabinoid levels, including THC. This was particularly evident in cannabis oil samples, a form of the plant that is more volatile than the cannabis flower.

At what temperature does thc degrade?

The degradation of thc can depend above all on high temperatures, in fact with too high temperatures for too long the thc loses most of its active ingredient. In most cases, however, with adequate temperatures such as 110° for about 45 minutes, the thca transforms into thc, instead if even higher temperatures are used with much more time than the pre-established one, cannabis loses a large part of its active ingredients, degrading the thc present in the inflorescences.

Sun exposure lowers thc level of cannabis plants

Leave it out in the open.

The air we breathe contains a number of oxidizing agents, oxygen being the most widespread. When cannabis is exposed to oxygen, a reaction at the molecular level causes the plant’s cannabinoid structure to change.

The same 1999 study that determined the fasting of thc degradation over a 4-year period found that the deterioration of thc was related to an increase in cannabinol (CBN) levels. this is because when oxidized, the thc converts to cbn.

CBN is a non-psychoactive cannabinoid which, while indicative of an old herb, has some therapeutic utility. in fact, CBN is believed to play a significant role in the sedative effect cannabis has on users. this makes it a valuable treatment for insomnia. furthermore, CBN exhibits antibacterial, anti-inflammatory, appetite stimulant, analgesic and glaucomatogenic attributes.

Since the only way to obtain cbn is through the oxidation of thc, this may be the only incentive to speed up the degradation process of thc. however, CBN is much less potent than THC and CBD, both of which have similar therapeutic capabilities and are capable of achieving them in much smaller dosages.

High temperatures for a long time.

Ironically, heat is also an essential ingredient in THC synthesis. Raw cannabis flower does not contain THC. Instead, loaded with THCA, the acidic and inactive precursor of THC, THCA does not produce the psychoactive effect that THC has.

THCA becomes THC during the decarboxylation process, or the exposure of weed to heat for any length of time. Cannabis and Cannabinoid Research published a 2016 study investigating the precise timing and temperatures for the most efficient decarboxylation processes.

According to this research, all THCA was synthesized to THC after raw cannabis was heated to 110 degrees C for 30 minutes, 130 degrees C for 9 minutes, or 145 degrees C for 6 minutes. However, as soon as the decarboxylation was completed, THC levels began to deteriorate. A blast chiller for fresh air would be a fairly effective solution.

In conclusion

Using these 3 combined methods or only one the thc level (but also cbd) of your plants will tend to decrease in percentage to the original level, surely a thc level of 0.75 / 0.80% can easily be lowered below 0,6% while keeping the quality of your inflorescences intact.

Sources: The scientific data used comes from the NBCI National Center for Biotechnology Information

In our Ebook section you can find over 40 books in 4 different languages follow the link to download all the books you want for free.


Grace Genetics team

Our team of cannabis experts publishes new and updated informational articles on current news from the world of cannabis on a weekly basis, as well as aids and guides on growing marijuana plants.

Leave a Reply

Latest News