Does Weed Expire & How Long Does It Take For Marijuana To Go Bad?

Sophia Delphi July 15, 2022 - 7 min read
Fact Checked

It’s a problem that most smokers can only dream of: a stash so big that they have to worry about whether their weed will go bad.

Those of us who find ourselves heading back to the dispensary (or calling our dealer) more often than we’d like to admit? We never have to worry about our flower expiring. We buy it, we smoke it, and then we need more.

But occasional cannabis users who find that their supply lasts much longer than they expected – and regular users who have to detox before a drug test – could be faced with that unusual question: does weed expire?

The question might also cross your mind after you’ve patronized a sketchy dealer and the bud just doesn’t deliver the experience that it should. Or if you’ve found a baggie in the pocket of a jacket you haven’t worn for a year or two.

We have good news. As long as we’re not talking about edibles (which contain other ingredients that can go bad), weed doesn’t spoil. You can still smoke or vape the bud that’s been hiding in a long-forgotten stash box.

That doesn’t always mean that you’d want to, though.

Illustration for Does weed go bad

Weed and THC

That beautiful, pungent cannabis you’ve just brought home will be at peak potency right after you’ve bought it. And as long as you didn’t get stuck with schwag, there should be a period of peak enjoyment on the horizon.

Of course, that’s largely because of the THC that weed is known for. THC has helped, though; the terpenes and flavonoids that provide the flower with its flavor and aroma also interact with the THC (and other cannabinoids) in weed to determine its full effects.

Here’s what some people don’t realize, though: when a marijuana plant is harvested, it doesn’t contain any THC. It contains a so-called precursor to THC, known as THCA. In order for a pot to have the effects you expect, the THCA must first be converted into psychoactive THC.

That conversion occurs when the flower is heated, so it automatically takes place when you smoke or vape weed. The heat that’s generated changes THCA into THC – so you’ll get high from the smoke or vapor without having to do anything else.

If you’re making cannabutter or cannaoil to be used in edibles, however, the bud has to be exposed to heat first. That’s why you put it into the oven for 30-45 minutes to “decarb” it before you can begin cooking. If you put the flower directly into your edibles, it won’t have its desired effect.

Why does that matter? Because if you have a stash of weed that’s been left untouched, the THCA has never been converted into THC. And THCA can get impatient over time.

What Eventually Happens To Weed

It’s not just heat that can affect marijuana. Light (particularly the sun’s UV rays) and even oxygen will trigger changes in THCA and the other cannabinoids in weed.

THCA eventually degrades into CBDA (the precursor to non-psychoactive CBD) and eventually becomes CBD; the longer the buds sit, the more THCA that “disappears.” So when you finally get around to smoking the bud, it won’t be anywhere near as potent as it was originally because there won’t be much THC in it. The terpenes may also degrade.

That process actually begins before the cannabis is even sold, but it will accelerate over time. CBD isn’t necessarily bad, since it may provide some medical benefit and help you sleep. But it won’t get you high. 

Chemical degradation isn’t the only thing that can happen to weed over time. There are more obvious changes that occur as well. The most likely issue is that the flower can dry out and become crumbly; it may still retain most of its psychoactive properties, but it will probably be difficult to smoke and it will taste nasty. The possibility that’s almost as likely is that the pot will grow mold or mildew, and will have to be thrown out.

How long before all of that happens?

It won’t be immediate. Some weed can easily last for six months, a year, or even longer. It can “go bad” relatively quickly, though, if your stash hasn’t been stored properly.

How To Extend Your Weed’s “Use By” Date

Image of Hemp Bud and Pocket Watch

You know by now that we’re not using that term literally. There isn’t a “use by” date printed on the bud you get from a dispensary (or from a dealer). But if the weed has lost most of its potency, or it falls apart when you pick it up, that’s tantamount to expiration.

And paying careful attention to how you store your cannabis is the only way to make sure your cannabis stays fresh and useable as long as possible.

Weed Containers

Don’t use baggies or other plastic bags. They’re transparent – and remember that light, especially UV light, can cause the weed to degrade. Just as dangerous to your pot: the plastic can build up a static charge that will fry the buds’ trichomes, and moisture will collect inside sealed plastic bags. The skunky smell can escape, too, which means that oxygen can get in. (Mylar bags are more acceptable choices than plastic, though.)

Don’t use a plain “stash box” or humidor for your cannabis, either. It may shut out the light, but oxygen can flow in easily and high humidity can also damage weed.

Mason jars have tops that seal more tightly than baggies, so they’re a better choice. They’re usually made from clear glass, however, so they have to be wrapped in dark plastic or towels before they’re put away. You can also double-seal them with duct tape to ensure that air can’t get in.

The best options:

  • Opaque smell-proof bags that you can buy online. They’re made from fiber and not plastic, they seal tightly, and they’re lined with activated carbon to absorb odors.
  • Specially-designed stash jars with airlock pumps. They use pressure to prevent any air from getting in (and any smell from getting out). If they’re not opaque, of course, wrap them in something dark to keep light out.

Two final notes. First, don’t stuff your stash jar or bag too tightly; that’s a prescription for mold growth. Two-thirds full is a good rule of thumb. Second, invest a few bucks in humidity packs, which will keep the atmosphere in your jars under control and preserve your precious flower.

Where To Store Weed

Marijuana will last longest and stay freshest if it’s stored in a dark area, at or slightly below room temperature. Once it’s hotter than that, moisture will accumulate and humidity will increase, making mold growth much more likely. Storing weed in the refrigerator is an equally bad idea; fluctuating temperatures in the fridge (or freezer) will also cause THCA to degrade.

A closet or pantry is ideal because it can be closed off from the light and will usually stay right around the same temperature as your house or apartment. Cabinets or drawers can work too, as long as they’re not near a heat source like the stove. Stay away from the attic or basement, though, because temperatures can get much too high or too low at some times of the year.

In short, use common sense. The way to keep weed potent and fresh as long as possible is to give it exactly what it needs: mild temperatures and an environment without light or airflow.

And just to repeat, your weed won’t spoil just because it’s old, and it doesn’t have an actual expiration date. You can’t get sick from smoking or vaping “vintage” weed. It simply won’t be very good if it hasn’t been stored properly.

Does Weed Expire Or Go Bad? FAQ

Q: If you store your stash properly, how long should it last?
A: That depends, at least in part, on how well the weed has been dried and cured. Six months is likely; a year or more is possible. There have even been published reports about one experiment which found that cannabis survived – in potent form – five years after being stored in an airtight jar.

Q: Does that mean you can just put your pot in an ideal storage environment, let it sit, and it will be fine to smoke in six months?
A: Not exactly. You should always check your weed regularly for signs of mold or mildew; if you catch it immediately, you can remove the affected buds and save the rest. If not, you may come back to find that your flower smells like ammonia and it’s only fit for the garbage can.

Q: Can you still smoke weed that’s started to degrade?
A: Yes. It may just be difficult to pack if it’s crumbling – and it may taste like crap (and not get you high) if most of the THCA has turned into CBD.