Seeds should be very dry before they’re stored. Bang a bean with a hammer. If it shatters, it’s dry. Or, bite the seed. If you leave tooth-marks, they’re not dry enough.
Store seeds in glass jars with tight fitting lids in a dry, cold, dark place – safe from insects and rodents.
Label with the name of the seed variety and the year harvested. You may also add notes about the growing season, or keep a diary for your garden.
The more carefully the humidity, temperature, and light are controlled in their environment, the longer they last. Humidity is more significant than temperature.
In a typical home, they may last as follows:
1 year: onion, parsley and parsnip
2 years: sweet corn, leek, pepper
3 years: beans, carrot, Chinese cabbage, pea, spinach