Got some old, unplanted seeds lying around in envelopes from last year, or even the year before? Wondering whether they’re viable? University of Minnesota Extension Service to the rescue! Here are some general guidelines from my “Vegetables” textbook:
Seeds that last 5 years:
Seeds that last 4 years:
Seeds that last 3 years:
Seeds that last 2 years:
Seeds that last 1 year:
I should put a giant * here, and say that these averages are based on storing your seeds in nice conditions — that would be room temperature, with low humidity. If they smell rotten or funny they are probably no good. If you kept them in your garage, the temperature swings probably did them in.
I would also still sow seeds just a little more thickly if they’re older. You can always thin out the seedlings later. But this should save you some money if you have some old seeds lying around that you can use up.