Each winter, I start thinking about what seeds I may want to plant in my garden for spring and summer. Before I get too far in my planning, I first rifle through the half-empty packets of seeds left over from the prior year (and in some cases, several years) and wonder if any of them are still viable. I usually shrug, toss the seeds in the ground, and wait to see what happens. If the seeds don't germinate, then I buy some new ones. Obviously, this haphazard approach to planting is far from ideal because it can put me several weeks behind my intended planting schedule by the time I notice that the seeds haven't germinated.

But this year, I decided to do a little research about how long seeds last. I was a little surprised to learn that seed viability varies considerably with the type of plant. Seed viability also will vary depending on whether the seeds are have been pretreated or pelletized. I was less surprised to learn that viability varies even under optimal storage conditions.

Seeds should be stored in cool, dry, dark conditions. Place the seeds in an airtight, watertight container such as a jar with a rubber seal (like a baby food jar or canning jar) or a zip lock bag inside a jar. To keep the seeds cool (ideally, below 50 degrees), some people store them in a jar in their refrigerator or freezer.

Seeds in good condition and stored properly will last at least one year and, depending on the plant, may last two to five years. I found a quite a few tables on the internet indicating the average shelf life of vegetable and flower seeds that are properly stored. Those sources are listed below. Here is a shorter version for a variety of vegetable seeds:

• 1 year: onions, parsnips, parsley, salsify, and spinach
• 2 years: corn, peas, beans, chives, okra, dandelion
• 3 years: carrots, leeks, asparagus, turnips, rutabagas
• 4 years: peppers, chard, pumpkins, squash, watermelons, basil, artichokes and cardoons
• 5 years: most brassicas, beets, tomatoes, eggplant, cucumbers, muskmelons, celery, celeriac, lettuce, endive, chicory

(Source: Johnny's Selected Seeds http://www.johnnyseeds.com/t-faq.aspx#questionshelflife)

If you are uncertain about whether seeds will germinate, you can do an easy germination test. Count out a specific number of seeds, anywhere from ten to one hundred seeds. Moisten a paper towel or a coffee filter and place the seeds on it. Fold or roll up the moistened paper over the seeds, making sure that the seeds don't touch each other, and put the paper inside a plastic bag in a warm place. Check the seeds after two or three days and then every day thereafter for a week or so. Spray the paper as need to maintain moisture. After the standard germination period has passed (as provided on the seed packet), count to see how many seeds have germinated and calculate the percentage of germination by dividing the number of seeds germinated by the number of seeds tested. Compare the germination percentage it to the germination rate (if there is one) on the seed packet label. If the seed germination rate is high, then the seeds are fine to plant. If the germination rate is low, you may want to purchase new seeds.

Sources for seed viability tables:

Vegetable seeds

• Iowa State University Extension: http://www.ipm.iastate.edu/ipm/hortnews/1995/3-3-1995/seedv.html
• Virginia Cooperative Extension: http://pubs.ext.vt.edu/426/426-316/426-316.html

Vegetable and flower seeds

• Clear Creek Seeds: http://www.clearcreekseeds.com/seed-viability-chart/
• Hill Gardens: http://hillgardens.com/seed_longevity.htm