By Master Gardener Jan Phipps
Occasionally, home growers ask Master Gardeners if it's okay to save unused seeds for the following year. The answer is "yes" with qualifications. Some seeds stay viable for multiple years depending on how they are stored and the plant species.
Seed packets usually have a date stamp which tells us what growing year the seed packet was created. Seeds do not expire as much as they lose viability over time, but we have some control over the seed's life span as gardeners.
Generally, seeds last for three years if stored properly. Even after three years, you can still get enough plants by sowing more seeds than recommended to make up for the ones no longer capable of sprouting.
What is the proper way to preserve seeds for future years? Cool and dry are the operative words. The choices include paper, plastic, or glass, with caveats. Paper envelopes work if you can control the humidity, keeping it low in summer and winter. A glass or plastic container with a tight screw-top lid keeps out changing humidity, but the seeds must be completely dry before sealing them in. It helps to use a small desiccant pack saved from something else. Rice can also be used but contain it in net pouches, or you will plant rice along with the desired plant seed.
Cool is the next hurdle. An attached garage that gets cold but never freezes in the winter works until it starts warming up in spring. Then move them inside to an air-conditioned house or dry basement for the remainder of the year. Some flower seeds need a chilling period which they receive in the garage during winter. Generally, seeds that easily self-seed outside might need cold stratification.
The following is a list of how long you can expect to save and use particular seeds, provided they have been stored properly. One year: onion, leek, parsnip, and parsley; two years: okra, peppers, sweet corn, and spinach; three years: arugula, green beans, lima beans, broccoli, carrot, lettuce, and peas; four years: beet, kohlrabi, brussels sprouts, cabbage, cauliflower, swiss chard, eggplant, tomato, kale, collard, mustard seeds, and rutabaga; five years: celery, bok choy, endive, melon, turnip, radish, and watermelon; six years: pumpkin, summer and winter squash, and cucumber.
As a rule, perennial flower seeds are good for 2-4 years, while annual flowers are good for 1-3 years. However, there are so many species and exceptions to the norm for flowers your results may vary.
Home growers also ask if one can plant the seeds from a green pepper purchased from the produce section of a grocery store. The answer is no. Farmers harvest edible sweet peppers before the seeds are mature, so they are not viable.
If you save unused seeds for multiple years, label them with the variety and year, so you know how old they are. When they reach the last year of recommended viability or beyond, try the over-planting trick mentioned previously.
The Illinois Extension Master Gardeners of Edgar County wish you a happy winter holiday season. Call us at 217-465-8585.