It is easy to be lured in by the glossy seed catalogs that arrive every winter, and order a lot more seeds than you have room to plant in one season. You might have end up with dozens of seed packets, including 8 kinds of lettuce, 5 heirloom varieties of tomatoes, and 6 different selections of radishes. Yet there might only be room in your small garden plot for one or two varieties of each vegetable. What is the best way to store all those extra seeds that you will not be planting this upcoming season?
Seeds are living things, and have to be stored under the right conditions to maintain their viability for as long as possible. The worst enemies of seeds are humidity and heat. More than anything else, too much moisture will shorten the life of your seeds. Ideally, the correct humidity level for seed storage is 10 - 12%, so they need to be stored at a low relative humidity level. Seeds should never be stored in a damp basement, or a warm, humid environment like a greenhouse, even for a few hours.
The ideal storage medium is a sealed glass jar in the refrigerator. Seeds can be wrapped in several layers of plastic bags for 3 or 4 years in the refrigerator, and germination rates will be high. Another good method of storing seeds is to vacuum seal them inside wide-mouth glass Mason or Ball canning jars with a Food-Saver vacuum sealer jar attachment. The seed packets should be vacuum sealed directly, as the process could crush the outer seed coating, and ruin the seeds for future planting.
Depending on the seed variety, some seeds have a longer shelf life than others. These include radishes, squash, turnips, and lettuce. Seeds with a shorter shelf life include onion, spinach, chives, and pumpkins.
If you have had seeds for a long time, you can check their germination rate by placing them between damp paper towels and placing them in plastic bag for a few days (on top of the refrigerator works well, and acts as a gentle "seed-starting" heat mat). If they sprout, they can be planted in the garden, and if they don't sprout, you haven't wasted valuable time and space in the garden waiting for them to come up.