As the gardening season winds down, you may find yourself the proud owner of a fair quantity of leftover seeds. If you are thinking that it seems like a shame to throw away this year’s seeds and start over next year, you are correct. Anything you purchased this year will almost certainly be viable next year if stored properly.
So how and where should you store seeds for maximum longevity? Here are five tips:
- Make sure the seeds are perfectly dry first. Purchased seeds should be dry. Homegrown seeds, on the other hand, whether from your own garden or that of a friend, should be checked before storage. Damp seeds will mold. (Check our vegetable guide for directions on saving seeds.)
- Seal seeds in airtight packaging. Some seeds come in packets that seal nicely. Paper packets should be sealed in a plastic sandwich or freezer bag before storage. Airtight food storage containers will also work. Gardeners who store seeds in glass jars often dip the mouth of the jar into melted wax to form a seal. Sealing the seeds will avoid damage from moisture and oxidization. Again, be sure that your seeds and packets are completely dry before sealing.
- Label packets with the variety and date. Purchased seeds will usually (though not always!) include this information. If your particular packet does not, write the variety and the date on the outside. Noting the variety will prevent confusion in future years. Writing down the date will let you know if your seeds are getting too old for good germination.
- Keep seed packets in a cool, dry, dark location. A basement or closet may qualify. The refrigerator is also acceptable, but if you go this route you may want to put a desiccant packet, a few grains of rice, or a cloth bag filled with powdered milk in your seed container to absorb moisture. Also, when you take your seed container out of the refrigerator, let it sit out at room temperature until it has warmed completely (up to 12 hours) before opening to prevent condensation from accumulating on the seeds.
- Do not store seeds in the freezer. Contrary to popular myth, seeds should not be stored for extended periods of time in the freezer. Some seeds are damaged by freezing. There are a few exceptions, such as native flowers and grasses, that will actually benefit from a short period of time at subfreezing temperatures. But unless you are dealing with a known exception, you are better off to avoid the freezer. (In case you are wondering, seed storage banks that rely on freezers use special flash-freezing techniques, keep their freezers at particularly low temperatures, and open the vaults very infrequently.)
Of course, no seed can last forever. Despite your best efforts, seeds with a high oil content, such as corn or spinach, may only last two years or so before going rancid. With proper storage conditions, however, many seeds can last five years. Some can last up to 10 years! A rare few can last even longer.
How to Test Seed Germination Rates
Not sure if your old seeds are still worth saving? Give them a fair trial with this easy germination test.