Meg Nanna

Storing cannabis long-term may not be a pressing issue for those who don’t have a great deal of it, or for those who consume it at a rate where long-term storage isn’t a really a concern. But be it a bountiful homegrown harvest, a great score made from your local dispensary, or a killer, uh, ”hook up,” how to best keep your weed in primo condition for future sessions is a worthwhile question. Working with the known factors—cannabis degrades when exposed to light, air, and heat—gives us a base from which to start. 

So, first things first: Containers should be airtight and block out light. Those handsome glass mason jars, while airtight, let the light in, so consider changing containers or blacking them out in some fashion. (There are sleeves for jars made of wetsuit materials such as neoprene that both block out light and give the glass an added buffer against bumps and drops.) Dropping in a Boveda pack helps regulate humidity—too much moisture in a sealed jar will result in mold, but if there’s not enough, it will get so dry that it’ll crumble when touched.

Adding to our pot preservation knowledge base is a new study from Italian scientists, who showed admirable restraint by using varying methods to store weed and hash for four years in order to determine which was best for preserving the THC. The scientists collected various high-potency hash and flower from law enforcement agencies, tested it for various cannabinoids (THC, CBD, and cannabinol, or CBN), and then stored the weed in several ways.

The testing conditions included varying degrees of light exposure, ranging from total darkness to 24 hours of light, and different storage temperatures, including room temperature, at a refrigerator temperature of 4 degrees Celsius, or in the deep freeze at -20 degrees Celsius.

The scientists discovered that the cannabis stored at room temperature, in both the light and dark conditions, had a reduction in THC by 13 percent (light) and 11 percent (dark). As THC denigrates, it converts into CBN, a non-psychoactive cannabinoid that has a sedative effect, so those numbers went up as well. 

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The refrigerated cannabis showed a slower rate of THC loss, although after four years, what was stored at room temperature and in a refrigerator had both lost nearly 100 percent of its THC. The cannabis that was stored in the freezer, however, retained virtually all of its THC and experienced minimal degradation. 

So if you have an extra pound you won’t be blowing through anytime soon, tossing it in the freezer is your best bet. Making some new friends and smoking it a bit faster works, too.