There’s three conditions to maintain to keep your prized heirloom seeds viable: keep them cool, dry and dark.
Seeds are embryos encased in a womb shell, or, as the Occidental Arts and Ecology Center explains, “A seed is a plant in a box with its lunch.”
Because seeds are alive, they’ll inevitably lose viability if exposed to conditions such as heat, sun or too much moisture.
The Seed Savers Exchange receives an average of five seed donations per month packed in all kinds of containers, including envelopes, film canisters or pill bottles, plastic baggies, manilla envelopes, paper bags and glass jars. All of these make great containers for long-term storage of seeds if a cool, dry and dark climate is maintained.
One of the best places for seed storage of less than five years is on a shelf in your bedroom closet. Or you can store seeds in the freezer for years—just remember to let the entire container of frozen seeds acclimate to warmer temperatures before opening the package.
And don’t forget to label your seeds.
To determine if stored seeds are still viable, take a few of them, count them and place them in a pot or flat tray filled with potting mix. Water the seeds well and give them plenty of light. Keep the potting mix moist, and see how many seeds sprout. If more than half to three quarters of the seeds sprout, then the seeds have a good chance of germinating in the garden, says Planttalk Colorado.
Want more information? Seed Savers offers a webinar on seed storage.