How long a seed remains viable depends partly on the type of plant, and partly on the conditions under which it has been stored. You can find a number of charts online that give seed survival rates by crop. I use the one in Robert Johnston’s little book, “Growing Garden Seeds,” available for $2.95 from Johnny’s Selected Seeds. It gives figures both for ideal storage conditions (fully dried, in airtight containers, in a cool, dark, dry place) and in more typical conditions (in their packets, in a box somewhere). Short-lived seeds that are only good for a year include onions and leeks. Umbelliferous crops such as carrots, parsley, parsnips, dill and celery don’t fare much better. The best keepers are tomatoes, cucumbers and melons. Most others fall somewhere in between.
If all seed companies stamped their packets with the current year, it would make this annual job easier, and rewarding, too, because leftover seeds save you money. But not every seed supplier does, and no one wants to waste time, garden space or even seed flat space with seeds not likely to germinate. (One solution, of course, is to mark each year’s purchases with the date.)
After you’ve tossed your “no way” packets, there’s another trick to finding the still-good ones, and that’s to test packets by pre-sprouting. To do this, sprinkle some seeds (ideally at least 15 or 20) on a moistened paper towel, fold and label it, tuck it into a plastic bag and set it in a 70- to 80-degree spot and count how many germinate. You can then assess whether it’s worthwhile to grow the rest (or even transplant the sprouted ones directly to flats if it’s sowing time). Wait at least a week or two to give them a chance.
So far, I’ve only gotten my four boxes down to three, so some tough love is still in order. But I’ve got a bizarre solution up my sleeve. I’m going to assemble a magical mystery mix of all the salad green packets, which constitute the bulk of my leftovers (mostly lettuces, Asian greens and other brassicas) and scatter them over a bed about 10 feet long in early spring. I’ll do the same with my collection of unplanted radishes. If not much has come up by the frost-free date, I might over-sow them with a collection of old beans. “Has-beans,” I call them.
Damrosch’s new book, “The Four Season Farm Gardener's Cookbook,” will be published in March.