If you have a weed stash you have not touched for a while, you may notice the buds getting dryer with time, and smoking them will not get you as high as it did originally. While aging is inevitable, it can be slowed down with proper preservation.
Like a fine wine cellar or whiskey barrel, properly dried and cured cannabis flower is best when kept in a cool, dark place. While there is no steadfast expiration date for cannabis, if you store it properly it should last about 6 months to a year before losing considerable potency and flavor.
Ideal temperatures for storing weed
To extend the shelf life of your weed, it should be kept in a cool, dark place at or slightly below room temperature. The ideal temperature to store your weed is below 70 degrees Fahrenheit, or 21 degrees Celsius.
High temperatures combined with high moisture activity and relative humidity can lead to mold and mildew. Mold thrives between 32 and 120 degrees Fahrenheit or 0 to 49 degrees Celsius, and growth is most active between 70 and 90 degrees Fahrenheit, or 21 to 32 degrees Celsius.
Excessive heat can dry out the cannabinoids and terpenes that have taken months to develop. When these essential oils get too dry along with plant material, it can result in a harsh smoke.
Lower temperatures also slow the process of decarboxylation of cannabinoids, the process in which THCA converts into the intoxicating cannabinoid THC. THC eventually degrades into CBN, a cannabinoid with different, non-psychoactive effects and properties.
Moisture levels for cannabis
Moisture and even water levels make a big difference when it comes to degrading the shelf life of cannabis. It can also get complicated for the average user to comprehend.
While no two cultivators dry their cannabis flower in the same way, all cultivators dry their flower 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 changing any of the cannabinoids or losing terpenes. Once the flower has the perfect moisture content, usually between 6% and 9%, it is placed into packaging from which excess oxygen has been removed. When you take it home, it is important to try to maintain that balance.
If you lose too much moisture, it can change the integrity of your flower. Your flower will become brittle and lose essential terpenes that affect potency and taste. On the other hand, with too much moisture and water, the consequences are worse.
In response to this modern quandary, 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 percent of water.
During storage, water activity cannabis should remain within a range of a minimum of 0.55 and a maximum of 0.65. Water activity increases with temperature, which is why light and temperature control go hand-in-hand as best practices for how to keep weed fresh.
The relationship between moisture content and water activity is complicated, and the cannabis industry is still striving to determine the optimal moisture content for packaged flower.
These discoveries suggest that a relative humidity level anywhere above 65% can significantly increase the likelihood that your weed will end up growing mold.
Light conditions for storing weed
Harmful UV rays break down many organic and synthetic materials. Similar to the way your grass turns brown at the end of a long sunny summer, or how a car’s paint begins to fade when it is not garaged, UV rays will degrade your cannabis over time.
A study conducted at the University of London in the 1970s concluded that light was the single biggest factor in the degradation of cannabinoids. The same study concluded that cannabinoids maintain stability for up to two years when stored under the proper conditions, though it can remain effective and safe to consume for much longer as the essential oils slowly break down over time.
Clear glass Mason jars are good at being airtight, however, they will not protect your flower the way an opaque container will. A brown or amber glass container will filter out ultraviolet light. Green-tinted containers also block out UV rays but not nearly as effectively as amber-tinted.
Storing your cannabis out of direct light will also help you control the temperature.
Air control for cannabis storage
While cannabis needs oxygen during growing and curing, storing your cannabis in a container such as a Mason jar with just the right amount of air is crucial to keeping it fresh and preserving its terpenes. Having too little air can greatly affect the relative humidity, especially if the buds are not completely dried before storage.
Too much air, on the other hand, will speed up the degradation process as the cannabinoids and other compounds are exposed to oxygen. There are a variety of hand and electric vacuum pump attachments available for canning jars that will help you minimize oxygen exposure.
In addition to playing a role in the conversion of cannabinoids, oxygen can also oxidize essential terpenes and change the overall aroma of the flower into a grassy, haylike smell.
To reduce exposure to oxygen, make sure there are not many air pockets in your container. You should always store your weed in an airtight container. Do not use very large containers to store small quantities of weed, as this leaves too much air inside the container.
Of course, it is inevitable that some amount of oxygen will get into your sealed package once it is open, but you can limit the amount of time that the jar is opened and the number of times it is opened.
How to store edibles
Cannabis edibles tend to store better in the fridge, especially if they are made with components such as oil, sugar, and flour. Edibles are prone to mold and go bad very quickly when left at room temperature, especially since most cannabis edibles do not contain a lot of preservatives.
If you are purchasing a commercial cannabis edible product, check the labeling for an expiration date to give you a good idea of what storage will work best. When possible, try to wrap edibles in wax paper or aluminum foil, as plastic might affect the taste. Place these wrapped edibles in an airtight container and put in the fridge.
Cannabutter can be stored in the fridge or freezer in an airtight container or glass jar. Cannabis-infused cooking oils should be kept in the refrigerator. Make sure not to put cannabis oils in the microwave and always use low heat for cooking.
How to store concentrates
Cannabis concentrates cannot be stored in just any container. Some consistencies of concentrate are not meant to be stored in glass jars. For example, most shatter will get stuck to the glass and is extremely difficult to get it all out.
On the other hand, a consistency like live resin is easier to scoop out of small glass jars.
Just like flower, concentrates should be left in a cool, dark place, under 70 degrees Fahrenheit. Storing it in the refrigerator also works.