Q: What is the best way to keep seeds for the longest shelf life?

A: Successful seed storage depends on many factors. Some seeds (bean, pepper, onion, etc.) are hard to keep viable for more than a couple of years. Others (beet, tomato, etc) can last 5 – 10 years under proper storage. Homeowners don’t typically have the resources to dry seeds sufficiently or to cool them low enough to be assured the seeds will sprout several years hence. The National Seed Storage Laboratory uses liquid nitrogen to keep seed viable but they still have to test their seeds for germination percentage every five to ten years.

If you harvest your seeds at the right stage, dry them with a commercial desiccant (silica gel products), and keep them at 0 – 5 degrees F. I think you could expect three years of viable storage.

Professional Seed Storage Instructions