How long do seeds last in mason jars?
Written by
Benjamin Miller
Reviewed by
Prof. Charles Hartman, Ph.D.When prepared properly, mason jars provide superior protection for seeds and can dramatically increase viability compared to a paper packet. In my years of gardening, I've definitely saved heirloom varieties for as long as 10 years in jars. The key is managing these three important factors: dryness, temperature stability, and total darkness during storage.
Preparation Protocol
- Dry seeds to 8-10% moisture using silica gel packets
- Sterilize jars in boiling water to eliminate mold spores
- Label clearly with harvest date and variety
Environmental Control
- Maintain below 70°F (21°C) with <10°F fluctuations
- Use desiccants: Silica gel or powdered milk packets
- Block light: Wrap jars in cloth or use dark storage
Monitoring & Maintenance
- Check seals seasonally for air tightness
- Inspect seeds: Annual germination tests
- Replace desiccants every 6-12 months
Seed type determines maximum jar longevity. Short-lived varieties, such as onions, typically last only 1-3 years, whereas tomatoes can last 4-5 years. I achieved success with cucumber seeds after 8 years in amber Mason jars. Temperature stability is critical; jars left in my cool basement Were Chosen over the pantry jars by three more years.
Controlling humidity is the key to the difference between success and failure. I maintain a relative humidity (RH) level below 40% using a pair of desiccants. The silica packets are placed under the lid, with rice sacks placed in between the seeds. My moisture meter consistently read about 35% RH with this technique. In contrast, it read about 60% RH in jars that had just a desiccant.
Utilize darkness techniques for optimal preservation. Amber jars block 99% light as opposed to clear glass. I wrap clear jars in aluminum foil if the sun shines on the storage location. This one step doubled the germination of my bean seeds after 5 years!
Start saving some of your favorite seeds in mason jars today. Use these methods to enjoy the flavor of homegrown tomatoes from seeds that are a decade old, as I do! Storing seeds in jars values gardening as a timeless legacy rather than a seasonal activity.
Read the full article: 5 Essential Tips: How to Store Seeds Properly
