Rose growing tips for the maritime Pacific Northwest
by Mary Robson, Area Horticulture Agent, Washington State University
Roses inspire gardeners to thoughts of garden romance, with dreams of bouquets of fragrant cream, yellow, red, and pink flowers, and arched supports holding scrambling climbers. In fantasy gardens, roses prosper with never a problem.
Reality, however, raises possibilities of blackspot, blasted blooms, and aphids scrambling instead of blossoms. How can roses be grown to best health in the often damp and cool climate of the maritime Northwest?
Selection of roses for cool summers is vital in this area. Many local rose-growers have tested cultivars and determined which ones prosper best here. Some excellent hybrid teas are "Honor" (white) and "Just Joey" (apricot). Floribundas, "Iceberg" and "Class Act," among others, do well. And for all-round sturdiness, tolerance of salt air in seaside locations, and disease resistance, consider Rosa rugosa and its many hybrids. A famous duo is R. rugosa "Rubra" and white R. rugosa "Blanc Double De Coubert," introduced in 1892 in France. Check with a nursery before planting, because roses that thrive in other sections of the country may not do well here. "Chrysler Imperial" is a good example; this is a luscious yellow rose that likes summer heat and won't grow well in Puget Sound regions.
Plant roses in a sunny, open area. At least six hours of direct sun a day gives the best bloom. Certain roses, such as some climbers like Mrs. Banks' rose (Rosa banksiae), will climb 20 feet to the tops of trees in search of light and bloom in competition with tree leaves, but most will not cope with shade well.
Badly drained soil also discourages good rose growth. They won't grow in heavy clay, waterlogged soils. Prepare the ground properly before planting by loosening the soil down to 18 inches, and thoroughly mixing in well-composted organic materials. Spread about four inches on top of the soil and dig it in. Don't use fresh manure of any kind, or fresh sawdust. Add about one inch of compost each year as a mulch on established roses. Don't cultivate heavily around the roots of roses once they are in, for this will damage little feeder roots.
Prune properly in early spring. Roses bloom on new wood, on canes or branches producing during the current growing year. Prune between Feb. 20 and the end of March in the Puget Sound region. Cut long canes back to 18 inches on hybrid teas, grandifloras, and floribundas. Prune out all dead and weak canes, opening the bush to light. Climbers are pruned in a different way, allowing long canes to develop and be tied up along a support. These canes live up to five years, producing flower buds on laterals off the main canes. Don't cut a climber way back; all wood for bloom will be gone.
Roses require regular water and fertilizer for best performance. The soil pH should be about 6.0-6.5, as for a vegetable garden. Indeed, roses do best in exactly the conditions of well-drained soil, sun, and fertility needed for a good vegetable garden. Add a handful of phosphorous (1/2 cup bone meal or superphosphate) to the bottom of the hole when planting, for each bush. If the rose is already established, provide a regular fertilizer regime. Liquid fertilizers such as fish fertilizers or commercial liquids work well. Fertilize monthly from March through July, but do not fertilize later than Aug. 1. Fertilizing stimulates new growth, and it's not appropriate because the plants must harden off for winter. New leaf and cane growth that appear after September is likely to be killed by winter, and the entire bush may be damaged by cold. Washington State University pest management experts do not recommend using a combination fertilizer-insecticide on roses. Combination products often result in applying chemicals where none are needed.
Watering regularly is vital to the continued health of roses and to producing the leaves that support vigorous flowers. Be sure that the rose receives at least an inch of water a week during the active season, either through natural rainfall or supplementary irrigation. If possible, apply water at the roots rather than sprinkling it on; keeping the leaves dry helps to reduce disease problems in summer.
Visit WSU's Agriculture Site on the World-Wide Web at http://www.cahe.wsu.edu.