The new year's seed catalogues sprout the annual question: Can leftover flower and vegetable seeds be used again? In many cases, yes. Even though, in general, the fresher the seed the better the germination.
Home gardeners are not likely to notice much difference from last year's seeds and will probably need to thin seedlings if they follow planting instructions.
Vegetable seeds that are fairly simple to store at home for three to five years include tomato, pea, bean, lettuce, beet, cabbage, cauliflower, radish, carrot, cucumber, watermelon, squash, spinach and eggplant.
Long storage also is possible for flower seeds such as marigold, zinnia, pansy, petunia, verbena, cosmos, nasturtium, dianthus, stock, sweet pea and alyssum.
Onion, sweet corn, parsley, strawflower and candytuft are among those with the shortest shelf life.
A simple viability test is to put a few seeds on a moist paper towel, fold them inside and keep the towel moist for five to 10 days at room temperature.
It's rare that every seed will begin to develop roots, but if some do, the remaining seeds in a packet are usable. If none germinate, buy fresh seeds.
Keep in mind, of course, that even if the seeds are viable, germination still will not take place after planting unless moisture is consistent, planting depth is correct and a specific temperature range is met. Seed packets usually include such guidelines. Most seeds germinate best between 80 and 95 degrees Fahrenheit.
Commercial seed producers dry fresh seeds to the correct moisture content before storage. While this moisture rate varies by species, the commercial process provides home gardeners with the clue on how to save excess seeds for more than a year--keep them dry.
A glass jar with a top makes an excellent moisture-resistant container. Store in a cool, dry place, and be sure to keep the seeds in the original packet so that you will know what they are, their age and the recommended planting instructions.
Saving seeds from your own plants is worthwhile only if the plants were open-pollinated; that is, non-hybrid. If the seed packet says the seeds are F1 or F2, forget it. Such seeds may germinate, but the resulting plants are likely to be inferior.
Open pollination means that the seed was produced by natural processes. Gardeners for thousands of years have collected seeds from their most desirable plants for the next crop. Such seeds are sometimes referred to as heirloom seeds, since they are handed down from generation to generation.
If you want to try and save seeds of an exceptional vegetable or flower, be sure to dry them properly.
A simple method is to spread harvested seeds on paper towels in an airy place. Moist clumps need to be broken up from time to time. A week of this treatment is usually sufficient.