Perennial flowers are gaining in popularity. The sense of permanence they bring to a garden is not immediate, though. Many perennials need about three years to settle in, spread and bloom abundantly. Dramatic 5-foot spikes of delphiniums, arching waves of orange day lilies, and creeping sunny yellow flowers of helianthemum are well worth the wait.
Just because perennials come up every year doesn't mean they need no care. Weeding is necessary, and the plants need occasional renewal by being dug up, divided and replanted. Peonies, lavender, lupine and baby's breath rarely need renewal, but campanula, coral bells, Oriental poppy, phlox, coneflower and yarrow need renewal every three or four years. Aster, bee balm, coreopsis, daisy, black-eyed Susan and chrysanthemum are among perennials that need this treatment every year or two.
Plan before you plant perennials. Design your garden on paper, where adjustments can be made with an eraser rather than a shovel.
Consider season of bloom, height and color in perennial flower plantings. Group perennials that bloom early, midseason and late if you want continuous bloom. There are perennial flowers to bloom in every season, from late winter's Christmas roses and snowdrops to spring's columbines and peonies, summer's delphiniums and day lilies and autumn's asters and goldenrod. Alternatively, you might plan for a maximum show in one season--a fall garden of ruddy chrysanthemums combined with New England asters, for example.
Put in at least three plants of each perennial. A single plant or two of any perennial will look too lonely for too long, even for those that eventually spread. Three to five plants of each sort is the minimum needed for bold effect.
Pay attention to directions for spacing. Plants might appear puny when young but will robustly fill their allotted spaces by their third year. Perennials that need frequent division spread most rapidly and need elbow room.