Store unused seeds in a dark, dry spot

QSeed packets almost always hold more than I can use, so I always have “leftovers.” How many years will seeds keep before they will no longer germinate? Should I be keeping seeds in the fridge or freezer?

AIt’s wise to take stock of stored seeds early in the year, to avoid purchasing duplicates. To know at a glance how old seeds are, make it a habit to write the year on each newly acquired seed packet.

Stored in dry, dark conditions with cool temperatures that fluctuate only minimally, most flower, herb and vegetable seeds retain their viability for about three years. Exceptions are onion, leek, corn, parsnip, verbena, zonal geranium (Pelargonium), salvia and larkspur seeds, which are best kept no more than one year for sowing a second time. Among seeds that commonly keep in good viable condition for five years or more are zinnia, nasturtium, cabbage, broccoli, cauliflower, kale, lettuce, radish, cucumber, squash, pumpkin, watermelon and cantaloupe.

Moisture and warmth are the major enemies of storage life in seeds. Ideal temperatures are between 0 and 5 C. Refrigerators can be used for storing seeds, if they are in airtight containers with packets of silica gel. Storage in a freezer is best for long-term storage, and only for seeds that have been kept thoroughly dry because moisture in the seeds will expand when frozen, damaging cell walls.

Test for germination by laying out 10 seeds in a line on a piece of damp paper towel. Identify them with a slip of paper marked in pencil with the date and variety name. Roll up the towel, seal it in a plastic bag and place it in warmth. Check regularly over 10 to 14 days. If less than half the seeds show root growth, buy fresh seed. Germination percentages between 50 and 90 will indicate how thickly the seeds should be sown.