Perennials also are not really substitutes for annuals. Most annuals bloom for much of the summer with often quite spectacular displays of color. Perennials, on the other hand, often bloom only over a period of 2 to 4 weeks, with a much less striking display than annuals such as petunias, impatiens or marigolds. Yet perennials offer something different, and the home gardener can have blooms all summer by carefully choosing a combination of perennials. The soil should have good drainage, but retain adequate moisture in the summer.
Most perennials do best in full sun, although many tolerate shade, and some even prefer it.
Begin by spading the soil to a depth of 8 to 10 inches. Remove any rocks, roots, or large stones. If the soil is very sandy or a heavy clay, add organic matter such as rotted manure. The heavier the clay soil, the more organic matter you'll need to add. Test the soil to determine if lime and nutrients are needed.