CORVALLIS, Ore. - Home gardeners are often frugal by nature. They save leftover garden seed from one year to the next and so forth.
Each type of seed typically remains viable and grows into healthy seedlings for only a certain average number of years. If your seed envelopes date back to the 1980s and 1990s, you'd be better off chucking them and buying new seeds for this spring's planting season.
To be absolutely certain they are really too old, you can test their germination with a few seeds placed in a wet paper towel in a warm room.
How long garden seeds last depends on what kind of seeds you have and how you store them, explained Oregon State University vegetable researcher Deborah Kean.
If seeds are kept dry, they last longer than in more humid conditions. For example, seed saving on the west side of the Cascades is more difficult than on the east side where it is drier.
Some types of seeds are naturally more short-lived than others. Parsnip seeds almost never last more than one growing season, no matter how they are stored, said Kean. Spinach and allium (onions and leeks) seeds also are relatively short-lived.
The amount of oil in seeds correlates somewhat with how long a seed tends to remain viable. Generally, the higher oil content seeds decline in germination rate more quickly.
Seed is best stored through the winter at 40 degrees at 50 percent humidity. A good way to store unused seed packets is to place them in a sealed jar with a desiccant such as powdered milk or rice at the bottom (to absorb moisture). Rice can be reused again as a desiccant if you dry it in the oven at a low temperature. Store your seed jar in the refrigerator or a cool area, such as a basement.
Average seed life for common homegrown vegetables and flowers are given below. These seed life spans reflect no special care taken. If you keep your seeds dry and cool, you can expect many of them to last longer than the time periods indicated here, especially beans, peas and corn.
Bush and pole beans - 3 years
Beets - 2 years
Broccoli, Brussels sprouts, cabbage, cauliflower, and kohlrabi - 3 to 5 years
Carrots - 3 years
Collard, Kale - 3 to 5 years
Sweet Corn - 2 years
Cucumbers - 3 years
Leeks, onions - 2 years
Lettuce - 2 years
Melons - 3 years
Oriental greens - 3 years
Parsley - 2 years
Parsnips - 1 season
Peas - 3 years
Peppers - 2 years
Radishes - 4 years
Rutabagas - 3 years
Spinach - 1 season
Squashes - 3 years
Swiss Chard - 2 years
Tomatoes - 3 years
Turnips - 4 years
Flower seed – annuals are generally good for 1-3 years and perennials for 2-4 years.