The environment in which a cannabis plant is grown, its genetics, fertilization and pest control practices each have profound effects on the end-product ultimately consumed by a user, however cannabis storage is also a key component in maintaining overall quality and freshness of the plant after purchase. Cannabis needs just the right balance of conditions to remain potent, intact and problem-free in the days, weeks or months after purchase. Over the years, cannabis packaging in legal or medical marijuana regions has become more sophisticated, with features designed to preserve shelf life. Cultivators go to great lengths to ensure their cannabis flower is packaged with optimal moisture content, usually in opaque packaging to keep the light away, and will often go to lengths to remove excess oxygen from packaged cannabis – even inserting nitrogen into packages to preserve freshness.

As naturally occurring terpenes in cannabis are exposed to environmental changes over time, they can oxidize or evaporate, creating changes in aroma and effects. Even though all cannabis naturally degrades over time and becomes less potent, the process can be slowed by following the steps below from WeedMaps.com on how to best preserve your cannabis.

Moisture Levels in Cannabis Flower

Moisture and water activity make a huge difference when it comes to diminishing the shelf life of cannabis. Loosing too much moisture or water activity when packaging or storing cannabis may change the integrity of the flower by becoming brittle and it can lose essential terpenes that affect the potency and taste.

Too much moisture or water activity found in cannabis flower is taken more seriously. So serious, in fact, The American Society for Testing and Materials (ASTM), which develops technical standards across many commercial industries, published the “Standard Specification for Maintaining Acceptable Water Activity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower” in May 2018. These ASTM standards guarantee that cultivators take extra care to ensure all cannabis flower is packaged with the perfect moisture content. Too much moisture can highly increase the likelihood that cannabis will develop mold or mildew and can be very harmful when consumed. The ASTM advises that water activity increases with temperature, which is why light and temperature control go hand-in-hand as storage best practices.

All cultivators are also required to undergo a process called “curing” to dry their cannabis flower and make sure it contains the perfect moisture content. Curing the cannabis allows the moisture that is trapped inside the bud to slowly dissipate from the flower without changing any of the cannabinoids or losing terpenes while retaining the volatile oils. After curing the cannabis, it is placed into packaging where excess oxygen has been removed. It is important to try to maintain that balance when purchased off of the shelf.

Light and Oxygen Exposure to Cannabis

Exposure to light, especially ultraviolet light, is the biggest culprit when it comes to aging cannabis. Light is the single largest contributor to loss and deterioration of cannabinoids. 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, hay type of smell.

While the clear glass jars used to display marijuana in the marketplace look nice, they do not block out light the way an opaque container would. WeedMaps.com suggests storing marijuana in a brown, glass container. They claim the beer bottle industry bottle their beverages in them to prevent the UV rays from damaging the acids found in the hops, which produces a “skunky beer.”

To reduce exposure to oxygen, do not use very large containers to store small quantities of weed. Try to avoid using the plastic sandwich bags but if it is the only option, remove as much air as possible before sealing. When using a glass jar, try to limit the amount of time and the number of times the jar is opened. For long-term storage, vacuum seal cannabis flower in food-preserving bags and place in the refrigerator or freezer.

Extending the Shelf Life of Cannabis

  • Keep an eye on the harvest date on the packaging before purchasing cannabis products from a licensed dispensary.
  • Try to avoid excessive exposure to light, moisture, oxygen and extreme temperatures.
  • Use mason and preserving jars with durable rubber seals to store cannabis. Food safe integrity is what you need, not just a jar with good looks. Loosely fill the jar with well-cured nugs and fix the lid tight.
  • To reduce exposure to the elements, when it is time to open the container, pull out the cannabis flower and immediately close the package. Don’t just let it sit open, and avoid windy or highly ventilated areas.
  • To maintain the right level of moisture, use a salt-based control sachet to maintain the ideal relative humidity. According to the ASTM standards, “a salt-based control sachet designed to maintain a relative humidity of 0.55 to 0.65 in a sealed container can be used to maintain optimum storage conditions.” This will not reintroduce terpenes that were lost, but it will ensure that you don’t have a harsh smoking experience.
  • Keep in a cool, dark place. An ideal temperature when storing would be below 70 degrees Fahrenheit or slightly below room temperature. High temperatures combined with high moisture activity and relative humidity can lead to mold and mildew and can dry out your flower and volatilize, or evaporate, sensitive terpenes, which will ultimately change the effects and taste of the flower. Lower temperatures are not as problematic, but they will reduce the potency of the flowers when they are smoked, or could make the trichomes brittle on the plant, causing them to break off when they are removed from the cold environment.