Whether your state has a medical marijuana program, legal adult-use weed, or both, cannabis packaging has come a long way in recent years. These days, marijuana products are likely to have a harvest date on them, but very rarely does flower come with an expiration date. So even with packaging improvements, you’re probably still left with the age-old questions: how long does weed last and how can you keep weed fresh?
In this article, we’ll review why it’s important to store your weed properly, how to keep your weed fresh, and how long weed lasts in ideal conditions.
Why proper cannabis storage is so important
Moisture is the biggest threat to the shelf life of cannabis. Overly moist cannabis can also have serious health consequences, namely by encouraging the growth of mold and mildew. These risks are so serious that the American Society for Testing and Materials (ASTM), which develops technical standards across many industries, published the “Standard Specification for Maintaining Acceptable Water Activity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower” in May 2018.
The ATSM defines water activity as “the (quantitative) capability of the cannabis flower in a sealed container to affect the humidity of the container’s headspace air.” Headspace is the air that surrounds the flower. Water activity measures vapor pressure against pure water. If water activity is 0.55, it is 55% water.
A relative humidity level anywhere above 65% can significantly increase the likelihood that your weed will end up growing mold. According to the American Herbal Products Association, the drying process will dehydrate cannabis until it has a moisture content of less than 15%, and the curing process is where the remaining moisture is slowly removed to retain the volatile oils.
So, too much moisture is bad, but lose too much and it can change the integrity of your flower. For example, your flower could become brittle and lose essential terpenes that affect potency and taste.
Luckily, the process of striking the perfect balance starts way before you buy weed. While no two cultivators dry their flowers in the same way, all cultivators dry their flowers and then put them through a process called curing.
When cannabis is properly cured, it allows the moisture that is trapped inside the bud to slowly dissipate from the flower without damaging the cannabinoids and terpenes. Once the flower has the perfect moisture content (typically between 6% and 9%), it is placed into packaging from which excess oxygen has been removed. When you take it home, it’s important to try to maintain that balance.
Proper storage involves keeping the water activity of your cannabis within a range of 0.55 and 0.65. Water activity increases with temperature, which is why light and temperature control go hand-in-hand as best practices for keeping buds fresh.
The Chemistry of Keeping Weed Fresh
It’s important to understand how air temperature, humidity, and light interact with the chemistry of your cannabis. When you know how to control those factors, you’ll be able to keep your reefer really fresh for longer periods of time.
It’s important to store your stash in a spot with cool, but not cold, air temperatures in order to preserve the psychoactive potency of your pot.
Decarboxylation is the process by which raw, organic, cannabinoids in their plant form (such as THC, CBD, CBN, and CBG) are activated so that the natural endocannabinoid system in your body can reap the benefits.
There are so many advantages to fresh decarboxylated weed that we couldn’t possibly ever list them…even in one single run-on sentence.
The thing is, the THC in your weed will lose its euphoric kick and degrade into the cannabinoid CBN (which will still help you get to sleep but won’t get you high) if you leave it out in the heat.
The aromas and medicinal properties of the terpenes in your weed will also dry out, making your medicine harsher and less healthy to smoke.
And if that’s not bad enough, mildew and other mold may be more likely to manifest on your marijuana from the moisture which accumulates in air temperatures of 77° Fahrenheit or warmer.
Many who read the above information will immediately think, “Put it in the freezer!” But you don’t want to freeze your reefer in an attempt to preserve it in spite of what some sources will suggest.
Yes, super cold ice water, high proof alcohol, and even dry CO2 ice are excellent ways to make the cannabinoid-laden trichome resin freeze up and fall off of freshly harvested sensimilla if you want to make cannabis concentrates for vaporization, edibles, or tinctures.
But if you store your buds in the freezer, the trichomes will break off and ruin the short- and long-term smoking potential of your pot. Don’t do it.
- Lost THC
As weed is exposed to heat, oxygen, and UV light, the cannabinoids within, including THC, will begin to break down. It doesn’t happen too quickly, but the change can become noticeable after a few weeks. It won’t leave you sober, but a joint won’t get you as high as the one you rolled when you first got it.
- Conversion to CBN
As that THC breaks down, it doesn’t just disappear. In fact, it’s converted into another cannabinoid, known as CBN. This cannabinoid has some mild psychoactive properties, but it doesn’t get you high on its own. This conversion mainly occurs when weed is exposed to oxygen and heat, although the process takes time.
- Lost Flavour
Lost THC won’t be the only consequence of keeping your weed in a warm spot. As it gets weaker, it’ll also taste and feel harsher upon smoking. This, of course, is a result of the terpenes drying out over time. Excessive light and moisture will bring about their downfall as well.
Does This Also Happen to CBD-Rich Bud?
If you’re more inclined to smoke CBD-rich strains, you may wonder whether any of this applies to you. Well, since CBD is also a cannabinoid, and since the buds also have terpenes, it too can degrade with age. The high isn’t a factor, but you’ll miss out on the other potential benefits of CBD.
What Causes Weed to Age?
We’ve alluded to certain causes of weed ageing, but let’s go ahead and break the issues down into clear terms.
You have to maintain a very precise balance when it comes to humidity and cannabis. If your storage method introduces too much moisture, you run the risk of mould infestation. If it isn’t humid enough, though, the terpenes and cannabinoids will end up withering away. While they’re quite different outcomes, the unpleasantness is equal between them.
Often going hand-in-hand with excess humidity, high temperatures can hasten the degradation of cannabinoids and terpenes. Generally, you should make sure your weed storage area doesn’t get hotter than 25.5ºC (78ºF). Simply enough, this is because any environment between 25.5–30ºC (78–86ºF) is prime for mildew and mould growth.
In short, persistent UV light will land a heavy blow on the impact on terpenes, THC, and other cannabinoids. This is especially problematic in tropical areas, where it joins forces with humidity and heat to harm your stash.
- Container Materials
Lastly, while many aren’t even aware of this, your container’s base material can have a direct impact on your weed’s ageing process. See, while many place their weed in plastic containers, the material can cause your stash to “sweat”. This means, as with actual sweating, your plant will release its inner moisture. It’ll end up dry and harsh as a result.