Perennial flower glory for summer gardens
by Mary Robson, WSU Extension Agent
June brings the billow of peonies, the tall radiant spikes of blue, purple, and white delphinium, and bright fragile Oriental poppies to flower gardens. All these plants are perennials.
Annuals, such as marigolds or petunias, are one-season plants, completing their life cycle and going to seed in one season. Perennials are plants that come back year after year. The plant stores nutrients in its roots and survives to grow again in the spring season. Some perennials--peonies, hostas, German iris--can survive for decades in gardens. Others--columbine and carnations--may be short-lived, productive and flowering for only a few years.
Selecting the right plant for the garden means knowing whether the plants will receive sun or shade. "Sun" areas get at least six hours of direct light a day. Many perennial flowers need sun and won't bloom well without it: Delphiniums, German iris, peonies, Shasta daisies, and herbs like rosemary and lavender all require maximum light for best growth.
Shade gardens, where light comes through tree branches, is limited by hilly terrain or is cut off by buildings, can still hold beautiful perennial plantings. Hostas, leafy fountains of foliage in all types of leaf tints from distinctly "blue" to yellow-green, grow vigorously in shade. Hellebore for winter flowers, Bishop's Hat (the epimediums with elegant foliage), and Lady's Mantle (the alchemillas with tumbling yellow spring flowers) all do well in light or filtered shade. For both sun and shade, there are dozens of other choices.
Soil preparation makes the difference for perennial flowers. These plants, with few exceptions, need good drainage and well-prepared, deeply dug soil. When planting one or two perennials at a time, dig a large hole and mix organic amendments with the soil: compost, leafmold well-decayed, bags of composted chicken manure, or steer manure. When replanting or installing only one plant, add as much soil amendment as possible.
Texture and interest from perennials tucked into existing shrub plantings can immediately increase garden beauty. Around rhododendrons, add hosta, violets, or sweet woodruff. The only caution about planting near established rhododendron and azaleas is their root systems are shallow. Don't dig closely under the branches and near the trunks of rhododendrons. Add plants out at the edges of the rhododendrons, leaving plenty of root space under the plants.
Many perennial flowers will grow well without the addition of lime to the soil, but some do prefer soil with lime added. Check with the nursery about specific plant needs, and remember that some of the lime-lovers are delphinium, German iris, and peonies. These do well when the soil pH is 6.0-6.5, the same soil level required for a productive vegetable garden. These plants won't thrive next to rhododendrons, where the soil can be and should be more acidic.
Along with soil preparation, growing perennials requires patience on the part of the gardener. There's an old British rhyme about perennials: "The first year, they sleep. The next year, they creep. The third year, they leap." Photographs in books and magazines with gardens full of abundant bushel-basket sized plants were not taken in the first year of the planting. A good way to get a flower garden to look full in the first season is to plant annuals between the small perennials for more color.
Many public gardens offer excellent examples of perennial gardens, including the Bellevue Botanical Garden.
Visit WSU's Agriculture Site on the World-Wide Web at http://www.cahe.wsu.edu.