So you have decided to build up a supply of seeds. That's great!
How long will seeds last?
More specifically, how long will seeds remain viable with a decent germination rate?
This is a tough question because there are so many variables depending on how the seeds were saved, and the kind of seeds they are.
First, you should try to keep seeds cool. Not necessarily frozen, but at about 50F. A spare room, a basement or a garage are perfect.
They should also be stored in the dark. A simple envelope works well here.
Seeds need to be kept dry. If you live in a humid climate or are storing in an area that gets damp, we would recommend it. You can buy ready made desiccant packets, or simply use rice or dry milk for this purpose.
Still, how long? Probably not this long, but most seeds still have a good germination rate after a few years.
Other than that, it depends on the plant. Parsnips have a very short seed life, yet their cousins carrots can go for a few years.
In the end let your own experience be your guide. To get started though, and playing it on the safe side, here's how often you should change up what you have on hand:
Leeks and other from the onion family, parsnips.
Every two years
Corn, spinach, okra, peppers.
Every three years
Carrots, peas, broccoli, peas.
Every four years
Beets, cauliflower, kale, kohlrabi, brussel sprouts, cabbage, all squash inc. pumpkins, tomatoes, eggplant, swiss chard, watermelon.
Every five years
Lettuce, radishes, melons, turnips.
Most seed packets are dated. If you buy any that aren't just date them yourself. This makes it quite easy to keep your supply fresh.
Many gardeners will tell you that they have had success with seeds much older than what we listed, and it is true. You can test germination rates yourself by simply placing a few seeds between moist paper towels and waiting to see how many sprout. If they are viable, but not all sprout, just sow extra to compensate.