Yes, pot—even your pot—does expire.
The most common and harmless way pot “expires” is a decline in potency. Quick science lecture: Weed gets you “high” and “stoned” thanks to deposits of THCA (tetrahydrocannabinolic acid), which is converted into THC, CBD, and CBC, through burning or cooking it.
However, oxidization brought on by light, air, and warmth will break down THCA into CBNA (cannabinolic acid). When heated, CBNA does not produce THC (the stuff that gets you high) and instead offers up CBN, which just gets you kind of sleepy.
When weed loses its THCA, its doesn’t exactly go “bad.” It’s just makes you drowsy instead of high. While this sleepy intoxication has similarities with what you get out of smoking stony, CBD-high bud—hunger, lethargy, affable confusion, etc.—it lacks the same pleasurable kick and its effect goes away in minutes instead of hours. You can use it, but you won’t get much out of it other than maybe a good night’s sleep.
(Note that if CBD-high pot tends to make you depressed, CBN-high “expired” pot may do the same. In that case, give it away to someone who would appreciate it.)
Other than smoking it and noticing you’re not high, best way to tell if your pot has degraded to this stage is to give it a sniff. If no longer has that sharp, pungent stank, it means that the compounds in the plant that create that smell— terpenes and terpenoids—have broken down. Generally speaking, terpenes and terpenoids don’t degrade at quite the same rate as THCA, but given that they’re going through the same process of oxidization they’re a decent bellwether. Also, if your pot looks dry, colorless, and disintegrates to the touch, it’s a goner.
To stave off THCA’s conversion into CBNA, keep your stash away from light, heat, dryness, and any kind of disturbances (say, movement or even household airflow). Popping it into a vacuum-sealed glass, ceramic, or non-reactive container in a dark, cool (but not refrigerated) place will arrest the process for months or even years.
Here’s a quick primer on freshness and storage:
When storing, make sure your weed is moist enough to be physically pliable, but never wet. Weed quickly declines in full moisture or collects mold (more on that later). Here’s how to rehydrate dry weed safely.
There are methods for preservation that include stopping all oxidation in nitrous-filled cans, but that’s really for commercial purposes. There are even weed humidors! In the end, though, nothing currently available on the market can prevent the harmless expiration of your pot. It’s the circle of life.
As opposed to merely expiring, pot can actually go “bad” through mold, powdery mildew, or other kinds of fungal infestation. It’s rare to see pot at the legal or illegal commercial stage with mold or fungus on it, but both growers and users should be aware of the possibility.
Molds attach to plants being grown in conditions with poor airflow, too much moisture, bad soil practices, and the like.
For those of us with decent immune systems, smoking a bowl of moldy of pot is not significantly dangerous—just unpleasant. Mold and fungus makes weed rather disgusting and harsh to smoke.
For those with compromised immune systems, however, the spores can transition to the lungs and take root. Given that pot is a go-to for many patients suffering from chronic ailments or on a course of chemotherapy, the risk of a fatal infestation, while small, is real.
Mold is identifiable through black spots, rust-colored blotches, “furry” deposits, whiteness, filminess, “burnt” patches, and other telltale signs. Take a look at this video to get a good idea of what to look out for. It co-stars Julian Marley!
Now, if any of these pop up on your weed, there’s not much you can do other than throw it out. Yes, with certain kinds of mold you can in theory cut away the rotting plant and preserve the rest. That’s not something we would advise, however. Usually, these are problems that go back to the plant’s growth. Best to get a different batch of weed, and perhaps a different weed supplier.
