Roses Can Be Challenging
posted on March 2, 2009 3:31pm
517-432-1555, ext. 156
EAST LANSING, Mich.—Roses have a well-earned reputation for
providing a gardening challenge. Maybe that’s part of the attraction.
“You’re not likely to succeed with roses if you just plant them and forget them,” says Mary Wilson, interim Michigan State University Extension Master Gardener Volunteer Program coordinator. “It takes some effort to grow healthy, attractive roses.”
Selecting hardy cultivars and an appropriate planting site, planting properly, watering, fertilizing and protecting plants over the winter are all important, but you can do all of those things right and still fall short. Why? Because roses are on the menu for a number of destructive insect pests, and every part of the plant, from roots to leaves to flower buds, is susceptible to at least one serious disease.
“Roses, especially the hybrid tea roses that many people want to grow, require regular spraying or dusting to protect them against devastating foliage diseases and pests,” Wilson sums up.
The gardener who understands what he or she is taking on and still wants to grow roses needs to select cultivars that are hardy in the local climate and well-suited for the intended use: climbing plants for trellises or arbors, bush roses for flowers for cutting, miniatures for borders or containers, etc. Check cultivar descriptions for disease resistance and fragrance, also.
A good site for roses receives at least 6 hours of sunlight per day; a full day’s sun is better. If the choice is between morning sun or afternoon sun, morning sun is better—plants shaded in the morning remain wet with dew longer, Wilson explains, and moisture on the leaves favors the development of several leaf diseases.
A well-drained soil high in organic matter is best. Prepare the site by spading to a depth of 12 inches, she advises, and incorporate organic matter and a high-phosphorus fertilizer at a rate of 3 pounds per 100 square feet. Plant packaged dormant roses in April or early May; transplant container-grown roses anytime during the growing season except the hottest part of the summer.
The planting hole should be large enough to hold the root system
without crowding it. Build a small, cone-shaped mound in the center of
the hole, and spread the roots down the sides of the cone. Make sure the
graft union—the place where the top portion of the plant was joined
to the root system—is about 2 inches below ground level. Make the
hole deeper, if necessary. Once the plant is positioned properly, fill
the hole, working soil around the roots carefully so as to avoid
damaging them, water to settle the soil, and then finish filling it.
Mulching is recommended to control weeds and retain soil moisture. Provide an inch of water per week if rain doesn’t provide it. And fertilize regularly from late spring through mid- to late July. Fertilizing after Aug. 1 can cause a flush of late growth that will be susceptible to winter injury.
Pruning removes dead, damaged or unhealthy wood, improves the appearance of plants, and helps determine the quantity and size of flowers produced. It also opens up the centers of plants—this promotes quicker drying and better coverage by pesticides, Wilson points out.
“Roses that aren’t pruned soon grow into a bramble patch where disease is likely and flowers are small and of poor quality,” she adds.
When and how you prune depends on what kind of roses you’re growing, she notes. Damaged canes can be removed at any time. Climbing roses are pruned just after they flower to stimulate the new growth that will bear next year’s flowers. Bush roses are pruned in early spring just before growth begins to remove dead wood and weak growth and to shape the plants.
A fall cleanup is an important part of disease control, Wilson says. Removing fallen foliage and other plant debris also removes disease organisms that will otherwise overwinter to reinfect the plant in the spring.
Winter protection is necessary for all but the hardiest native roses to help plants survive low winter temperatures and injury from wind and fluctuating temperatures, Wilson says.
“Keeping roses healthy through the growing season is the first step in getting them through the winter,” she notes. “Roses going into winter stressed and weakened by pests, diseases and poor nutrition are much less likely to survive.”