Filling in the garden after the last frost

If you live in an area with a long growing season, you can go ahead and sow annual seeds straight into the ground, secure in the knowledge that they’ll sprout, grow up, and start pumping out flowers, all in plenty of time. This approach is generally easy and cheap. Gardeners with shorter summers can either start seeds inside or buy seedlings.
Freezing weather kills or at least severely damages most annuals. Therefore, the trick is to know your last spring frost date and your first fall frost date —these dates bookend the annual-gardening year. (If you don’t know, ask an employee at a local garden center, a more experienced gardener, or someone at the nearest office of the Cooperative Extension service. Note that the dates are averages; they can vary somewhat from one year to the next.)