Perennials are plants that, once planted, stay in your garden for more than two years. In general, they put up leaves in the spring from dormant roots, flower for three to four weeks, set seeds and, in the fall, die down to the dormant roots again. You need never buy them again and in fact they often multiply, but the short bloom time can leave you feeling deprived. Use them well for the greatest impact.
Forget the flowers. You'll be living with the foliage for a much longer time than the blooms, so make sure it's worthy of taking a place in your garden, of becoming a cool green background for the bright flowers you love. The leaves of some, such as daylilies, are linear and sword or grass-like. Others, such as hostas, are known for their bold, sometimes colorful, leaves. Astilbes are ferny, and many others, such as daisies, are simply medium. An easy way to make a garden look pulled together is to mix three of the four foliage textures in one bed. Mix medium, ferny, bold or linear and you'll notice an immediate jump in the interest it holds.
You can create a focal point by grouping plants with strong textures together. Farther on, give the viewer a restful interlude with an area of single-textured plants, followed by another focal point, perhaps with another, entirely different, group of textures. Go to a nursery and gather together plants that attract you. Group them in different ways, try out different combinations of textures.
Bright, compelling, exciting, flowers are the main show, and the short bloom time of perennials can often be turned into an advantage. Take a peony that blooms in May and set it within a bed of asters that won't bloom until September. Don't worry about color harmony with that grouping. Bright red oriental poppies can be paired with soft pink kaffir lilies without overlap, and so on.
Not all perennials, of course, stop blooming so quickly. A small, ferny plant called Corydalis lutea will flower without stopping from spring through fall, though most long-blooming plants such as daisies and yarrows may stop after a month and a half. Consult your local nursery for suggestions, and remember that deadheading, cutting off the spent blooms, encourages further blossom development.
One advantage of seasonal bloom is that you can use these plants to shift the mood of the garden to match the time of the year. Choose one bed for each season and pack it with all your favorites, aubrieta and alyssum for spring, daisies and echinacea for summer, asters and chrysanthemums for fall. Fill in with annuals for interest during off-bloom times or simply leave as a textured green space, attractive but not demanding attention.
One of the most enjoyable aspects of perennial gardening is creating groupings of plants that seem to enhance each other, to become a picture that is greater than the sum of its parts. You might take one of your favorites, bleeding heart, for instance, and then find partners to plant with it.
Look for plants like like the same conditions, shade or part-shade for the bleeding heart. You could add some of the purple leaved heucheras, a maidenhair fern, and a polemonium with pink flowers to bring out the pink in the bleeding heart. Go to your local nursery and try out combinations by putting pots together, making small beds of plants in an out of the way place, trying one thing, then another, before you buy. You're likely to find that the nursery professionals are quite happy to help, even enthusiastic about your project.
Most people plant annuals in their containers because they want color up front, all season, but perennials have a place in pots and planters, too. Again, use foliage for interest and contrast, flowers for an added bonus of color. Three different perennials, one each for spring, summer and fall, plus a long-blooming annual, can make a picture of long-lasting interest.