By Max Sargent

We’ve all found a baggy of weed down the side of the bed or in the back of a cupboard and wondered, should I smoke it? Does cannabis go off? If it only looks a little brown and crusty, we’ve got good news for you, it can be smoked! Though we can’t promise it won’t be significantly harsher than you’d like.

It’s not only bud that loses its lustre, but concentrates too. But how long does wax take to go off? And can you smoke lumpy wax? Again, we’ve got good news for you—you can! But read about nucleation (further below) first.

How Long Does Weed Last?

This is not an exact science, and the conditions your buds have been hiding in will determine what sort of state the cannabinoid content is in. For instance, if it’s been moist for a year, it’s likely not worth even trying. However, if it’s been in a cool, dry place, then it may well have a good amount of THC left in its crusted trichomes.

These are rough estimates, but it’s likely THC degradation will happen at around this rate:

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So in answer to the question, does weed expire? Yes, but not for quite a while. Even if it’s less potent than you remember, think of it as something of a delicacy.

How To Tell if Weed Has Gone Off

Fortunately, much like food, there are some telltale signs that should help you figure out if your weed has gone bad.


If your weed is just old, it will appear generally lifeless and dried out.

Look out for:

  • Brown colouration
  • Dry and crusty
  • Less full looking

However, these are no reasons not to smoke it. Though it may have lost some of its quality and flavor (and gained some harshness), these signs don’t indicate that there’s anything wrong with your weed. However, if you see mold growing on it, or if it appears wet or blackened, it’s best to just throw it away.


Old weed is likely to smell a lot less than it did. So if you find it fairly odourless, don’t worry—this is to be expected. It may even take on a subtle, earthy smell.

However, if it smells bad, don’t smoke it. If it’s developed any new, pungent aromas, this is likely a bad sign.


The effects are likely to be much gentler, as the THC will have degraded. Likewise, the CBN will have increased, as THC becomes CBN when it degrades. The effects of CBN are not psychotropic outright, but anecdotal accounts point to a sleepy sort of effect. As a result, you may find it more relaxing and less buzzy than most cannabis.


Old cannabis will feel dry and crumbly, grinding up very well!

Gone off cannabis may feel moist or even wet. In this instance, get rid of it.


Sadly, weed can go bad. In this case, as it’s organic matter, mold may well develop on it. The symptoms are fairly self-explanatory—namely, there will be some sort of deposit on it. Look for fuzzy white patches and any other off colors.

As well as being able to see it, it’s likely that it will smell noticeably off. Use common sense; if your senses are telling you there’s something wrong with it, trust them and don’t smoke it. You don’t want to find yourself smoking moldy weed!

Why Does Cannabis Lose Its Potency Over Time?

Over time, the cannabinoids present in cannabis will undergo chemical changes. Though seemingly minimal, these can cause major differences when ingested. When cannabis starts to go off, the THC is undergoing a chemical transition.

Cannabis tends to be harvested at the point at which the THCA content is assumed to be at its highest. THCA is the precursor to THC. It becomes THC when it undergoes decarboxylation (heating).

But it doesn’t stop there. Expose either THCA or THC to the atmosphere or UV light for long enough, and further changes occur. This time, both compounds become CBNA and CBN, respectively. The longer you leave the weed, the higher the concentration of new compounds versus old. Although CBN isn’t bad for you, it is different, and different isn’t always what people are after.

Why Does Cannabis Lose Its Potency Over Time?

What Happens if You Smoke Gone Off Weed?

If it has undergone the above process, then nothing bad will happen. It’s likely you’ll just find it less potent than before, but potentially more relaxing. CBN is not reported to have many side effects, at least not any that wouldn’t be present in THC-rich weed as well.

If, however, your weed has gone moldy, it could make you ill. So if you notice any sign of mold, get rid of it.

How Long Does Cannabis Wax Last?

It’s not just cannabis flower that can go off, but THC concentrates too. In fact, dabs and wax can go off more quickly than the buds. First off, if it gives off a significant weed-like scent, that means the terpenes are evaporating. In this case, you’re likely to have a subpar taste experience. However, this in itself won’t affect the cannabinoid concentration.

Concentrates in general have a shelf life of around 6–8 months at their original quality (if stored properly). After this, they will start to degrade. But much like the buds, this degradation doesn’t necessarily mean you can’t smoke them.

There’s hope for dabbers who want to avoid that sleepy hit of CBN. The cannabinoid evaporates at around 50°F higher than THC. So if you’ve got an e-nail with very specific settings, then you can set it to evaporate the THC and leave the CBN behind.

  • Nucleation

But how long does wax last? Eventually, concentrates will go through a process known as nucleation. Nucleation is essentially the process by which a substance crystallises. In water, it is how quickly it turns from liquid into ice.

Cannabis concentrates that have nucleated will have a sugary, crystalline appearance, though this doesn’t mean you can’t smoke them.

However, the lipids used to make cannabis concentrates might be harmful to smoke after nucleation. As these lipids gather together and solidify, they can be bad for you when inhaled. You should be able to spot them as they’ll have a white or off-white appearance. carla

How Long Does Cannabis Wax Last?

Storage and Quality

Preserving weed long term is a matter of proper storage. Basically, UV light, oxygen, and heat are your enemies. Therefore, keeping your weed in airtight, opaque containers in a cool environment is key to retaining potency for as long as possible. These are the best ways to avoid moldy weed and preserve quality cannabis.

Likewise, preserving concentrates long term is a similar matter. However, certain processes, such as nucleation, are inevitable. Nevertheless, following the above steps will greatly increase the lifespan of your cannabis concentrates. Moreover, winterising can help extend the lifespan of concentrates. Winterising is a process whereby waxes and lipids are removed from the concentrate. When this happens, nucleation is slowed, and it becomes less problematic when it occurs.

Aged Weed: Has It Matured To Perfection?

Many people wonder whether aged weed takes on the same quality—the same refinement—as a matured wine or a barrel-aged whisky. The answer is somewhat convoluted. Cannabis, unlike wines and whiskies, does not continually improve the longer it is cured. As we’ve seen, there’s a chemical process that happens within cannabis as it ages, and for most smokers, this will eventually reduce the quality of their bud.

That being said, there are still better ways to cure cannabis, and these can make the difference between a smelly, sticky bud and a perfectly dried, deliciously rich one. Curing cannabis is about drying it out in such a way that brings out the most in the terpene profiles and maximises the concentrations of the more desirable cannabinoids, such as THC or CBD. There are differing opinions regarding how best to achieve this, but mostly it involves controlled drying in the open air for anywhere between a few days and a few weeks and then completing the curing process in a sealed container (for which we have an in-depth curing guide).

So, unless by some extremely happy accident, it’s unlikely that the weed you’ve found down the side of your bed will have developed the sophisticated and elegant notes of fine wine. Nonetheless, as long as it’s dry and appears alright, it's probably still worth smoking!

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