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.
Bottom line: make sure your weed doesn’t get too moist and succumb to mold.
The best temperature to store your cannabis
The ideal temperature to store your weed is right around 70 degrees Fahrenheit (21 degrees Celsius). Why? High temperatures combined with high relative humidity can lead to mold and mildew — the nemeses of safe and healthy cannabis.
High temperatures can also dry out your flower and evaporate sensitive terpenes, but this should only concern you if you plan on using a flower vape with precise temperature control. After all, lighting up a joint with a flame is going to destroy most of them anyway.
Bottom line: store your weed in a cool place such as a closet or pantry.
How light and oxygen affect cured cannabis
Exposing your weed to light is the fastest way to age it. This has been known since at least 1976 when a study published in the journal Pharmacy and Pharmacology explored what happens to the stability of cannabis under various conditions. It concluded that light is the single largest contributor to loss and deterioration of cannabinoids and suggested that “carefully prepared herbal or resin cannabis or extracts are reasonably stable for 1 to 2 years if stored in the dark at room temperature.”
Ultraviolet (UV) light degrades weed. So, even though glass Mason jars may look appealing, they won’t protect your purchase the way an opaque container will. If you really like to look at your marijuana, a brown container will filter out visible UV rays. Fun fact: that’s why brewers use them to bottle beer. Green containers will also block out roughly 30 percent of UV rays.
Prolonged exposure to light and air will gradually convert THCA into THC and THC into CBN, a cannabinoid that does not create the intoxicating properties that THC delivers. In addition to playing a role in the conversion of cannabinoids, oxygen can also oxidize essential terpenes and give flower a grassy, haylike smell.
Bottom line: to reduce exposure to air, make sure to always store your weed in an air-tight container. Don’t use very large containers to store small quantities of weed, as this leaves too much air inside the container with your herb. It’s inevitable that some amount of oxygen will get into your sealed package once it is open, but you can keep the number of times you open your jars to a minimum.
The best way to store weed
Once you understand all of the factors explained above, how to keep weed fresh and store weed properly becomes much more intuitive. Among the worst ways to store your bud are on a tray exposed to oxygen and light, in a plastic sandwich bag, or in a clear glass jar or similar large glass container.
Cultivators go to great lengths to ensure your flower is packaged with optimal moisture content, usually in opaque packaging to keep light out. Some companies have even started replacing the oxygen in their packaged flowers with nitrogen to help maintain freshness. So you might be wondering why some dispensaries still feature clear containers. The short answer is old habits die hard. The practice of seeing and smelling the product on the shelf is still a key component for many people when it comes to deciding what to purchase.
For those who don’t care as much about seeing and smelling the product before buying it, it’s wise to buy smaller amounts of pre-packaged cannabis.
Bottom line: store cannabis in a cool, dark place in an air-tight container with as little air in the container as possible.
Extending the shelf life of weed
When stored properly, weed can maintain freshness for up to 2 years. But even if you don’t intend on preserving your cannabis for that long, knowing how to store weed properly will help you get the most out of your cannabis experience. Ultimately, the key to extending marijuana shelf life is all about limiting exposure to the elements. When it’s time to open your container, pull out your flower and immediately close your package. Don’t let it sit open, and avoid windy or highly ventilated areas.
To maintain the right level of moisture, use a salt-based control sachet — also known as humidity packs — to maintain the ideal relative humidity levels.
Additionally, you can store your marijuana in a cannabis humidor box, which has been designed to maintain the humidity for marijuana. There are currently several models available on the market.
Whatever you do, be sure you don’t use a cigar or tobacco humidor to store your weed. Cigar humidors are typically lined with cedarwood. The oils in the wood help enhance the taste of cigars, but those same oils tend to harm cannabis. Similarly, humidors for cigars often use sponges or propylene glycol to create humidity levels that are ideal for tobacco but much too high for cannabis.
In the past, to remedy dry weed, people would add an orange peel to their bags to keep the moisture content, but this greatly increases the likelihood that mold would be introduced. In addition, the water activity of orange peels is unknown and the aroma of the peel could alter the flavor and aroma of your marijuana.
Bottom line: use the same humidity packs, such as Boveda packs, to reintroduce moisture if it is too dehydrated. This will not reintroduce terpenes that were lost, but it will ensure that you don’t have a harsh smoking experience.