Then store in a cool dry location like a refrigerator. Seed that molds was not sufficiently dry before storage. Seed viability decreases over time. Parsley, onion, and sweet corn must be used the next year. Most seed should be used within three years.
Seed saving is essential for maintaining unusual or heritage vegetables and flowers.
It is a great way to propagate many native plants too. There are numerous seed saver exchanges, clubs, and listings in magazines like Organic Gardening. Although you shouldn't base your entire garden on saved seed you may want to give seed saving a try.