Should Cannabis Be Stored in Airtight Jars?

Short answer

Yes. Cannabis keeps potency and aroma in an airtight jar. Oxygen degrades THC and terpenes. A sealed jar limits the air that touches the flower. Use glass, not plastic. Keep the jar in the dark at 60°F to 70°F. Hold relative humidity inside the jar at 58% to 62%.

Why oxygen matters

THC oxidizes into CBN. CBN has weaker psychoactive effect than THC. Terpenes oxidize as well. The process needs oxygen, so less air in the jar means less degradation per day. Headspace matters. A jar filled 75% to 80% leaves little air for oxidation and still leaves room to handle the flower.

glass jars vs plastic jars for cannabis

Glass compared to plastic

Plastic bags carry a static charge. Trichomes stick to the walls and stay there. Plastic also takes on and releases terpenes, which changes the smell. Glass does not react with cannabinoids or terpenes. Amber glass and opaque jars block ultraviolet light. UV light converts THC to CBN and bleaches color.

Humidity control

Flower below 55% relative humidity crumbles and loses weight. Flower above 65% RH supports mold and mildew. Two-way humidity packs hold 58% or 62%. Add one pack per ounce of flower and replace it when the pack turns stiff. Do not add orange peel, bread, or lettuce. Those items add moisture unevenly and can carry mold spores.

Temperature and light

Heat drives terpene evaporation. A kitchen counter near a stove reaches temperatures above 80°F. A closet shelf at 65°F works better. A refrigerator is cold, but condensation forms each time the jar warms to room temperature. A freezer makes trichomes brittle and they break off at the stem. Store at room temperature in the dark.

How long it keeps

Stored at 60°F to 70°F, in the dark, at 58% to 62% RH, flower holds quality for 6 months to 12 months. After 12 months THC content drops and the smell flattens. Concentrates stored the same way last longer than flower.

Signs of poor storage

Hay or grass smell, which points to terpene loss
Dry, brittle flower that crumbles in the hand
White fuzz, gray patches, or a musty smell, which point to mold
Brown or yellow color, which points to light damage
Weak effect at the same dose, which points to THC loss

Discard flower with visible mold. Mold spores spread through the whole jar, not just the patch in view.