Marijuana seeds do not have a hard expiration date, but their ability to sprout successfully, known as viability, decreases significantly over time. Each seed contains a dormant embryonic plant surrounded by a nutrient reserve. While waiting for ideal conditions of moisture and warmth, the seed’s internal components slowly degrade. A seed’s lifespan can range from a few months under poor conditions to over five years when stored correctly, making preservation the key factor in longevity.
The Biological Factors Behind Seed Degradation
Even in dormancy, the seed remains biologically active, engaging in low levels of metabolic respiration. This slow internal activity consumes the seed’s finite stored energy reserves, causing a gradual decline in health over years. The primary cause of viability loss is the accumulation of damage to the seed’s DNA and cellular membranes.
Exposure to oxygen accelerates lipid peroxidation, a destructive process where fatty acids within the stored food supply break down and become toxic. Damage to the DNA builds up over time, eventually preventing the genetic instructions for growth from being correctly executed during germination. High temperatures and increased moisture content significantly speed up these degradation processes, quickly reducing the seed’s potential lifespan.
Maximizing Longevity Through Proper Storage
The goal of long-term storage is to slow the seed’s metabolic activity to the lowest possible rate without causing cell damage. This is best achieved by controlling three primary environmental factors: temperature, humidity, and light. For medium-term storage, a consistent refrigerator temperature is highly effective, ideally maintained between 37°F and 46°F (3°C and 8°C). This low temperature dramatically reduces the speed of internal chemical reactions that lead to degradation.
Humidity control is equally important, as excess moisture can promote mold growth or prematurely trigger germination. Seeds should be stored in an environment with a low relative humidity, typically between 20% and 30%. Using airtight glass jars or vacuum-sealed bags with a desiccant, such as silica gel packets, helps maintain this dry environment. Exposure to light, especially direct sunlight, can trigger metabolic processes and should be avoided by storing containers in a dark location. Under these optimized conditions, cannabis seeds can remain viable for five to ten years.
Testing the Viability of Older Seeds
Before attempting to plant seeds that have been stored for a long time, it is wise to test a small sample to gauge their current viability. The most reliable method is the “paper towel test,” which simulates the ideal conditions required for germination. To perform this, select a few seeds and place them between two sheets of paper towel moistened with water; the towel should be damp, not soaking wet.
Place the paper towel inside a plastic bag or between two plates and keep it in a warm, dark area, generally between 70°F and 85°F (21°C and 29°C). Check the seeds daily for three to seven days; any seed that sprouts a taproot is considered viable and ready for planting. Another common technique is the “float test,” where seeds are dropped into water, with the theory that viable seeds sink. However, this test is not foolproof, as viable seeds may float due to trapped air, making the paper towel method the preferred way to confirm embryo health.