Starting plants from seed has many practical benefits: You save money, get a head start on the growing season, and choose from varieties far beyond those locally available. You also get to experience the joy of watching a seemingly lifeless seed sprout into a living plant.
A seed is a plant embryo and its initial food supply is stored within a protective coating. Seeds remain dormant until a combination of moisture, temperature, air, and light triggers germination.
Seeds have different shelf lives. Some will remain viable for hundreds of years, whereas others may only store well for a couple of years.
Knowing when to start seeds indoors takes some backward thinking. Find out the average date of the last frost in your area and the number of weeks before that date you should start a particular seed. (The number of weeks varies and is listed on the seed package.) Then count backward on the calendar from the average last frost date.
As a general rule, start most seeds six to eight weeks before your average last frost date. If you start seeds too early, you'll have to keep the seedlings inside too long, and they will be weak by transplant time.