   Growing Roses Made Easy - July 9, 2003 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Few of us are devout rosarians, but many of us have a rose or two growing in our landscape. Contrary to popular belief, roses are easy to grow and can produce many fragrant, beautiful cut flowers throughout the growing season. Getting healthy stems, foliage, and flowers requires irrigation, fertilization, and proper pruning. It is not difficult, but you must observe the plants and follow a few simple guidelines. Roses need some soil moisture year round and regular irrigation during summer. Drought stress leads to defoliation and sunburn of canes while overwatering or poor drainage may lead to disease problems and/or nutrient deficiencies. Water can be applied through overhead, drip, or flood irrigation. It is critical that the water go deep (1½ to 2 feet) into the soil. Check the soil moisture with a long screwdriver to determine irrigation frequency - it should always be moist one inch below the surface. Deep watering twice per week is usually sufficient. Organic mulches will help conserve water and keep roots cool. Roses respond favorably to periodic fertilization during the growing season. You can purchase rose fertilizers and simply follow the label directions. A less expensive alternative is to apply ¼ cup of 8-8-8 or 10-10-10 per plant every two to three weeks starting two weeks after the plants leaf out and continuing through September. Be careful not to get the fertilizer on the canes and water it in after applying. Be careful with fertilizers. Misuse or higher than recommended rates of application can damage your plants. During the flowering period, remove spent blossoms to promote new flower shoots. Remove faded flowers by cutting below the stem to just above a five-leaflet leaf. Prune all canes to a 30- to 45-degree angle above a live leaf, leaving no more than ¼ inch of stub above the leaf. Remove any dying or dead stubs throughout the year to discourage the carpenter bee, a small pith borer that nests in tunnels bored into rose canes. If this insect is a serious problem, seal the ends of the pruned canes with a substance, such as common white glue, that discourages the bee from boring a hole down the center of the canes. Dormant season pruning of established roses varies with different rose types. In general, the object is to remove all dead or diseased wood; to remove old, weak or undesirable wood; and to shape the plant. For healthy growth, cut the canes back to live wood. A live cane has a white center and green inner bark. Prune to produce an open center and to shape the plant. After a severe winter, only a few inches of healthy cane may be left on hybrid teas and grandifloras. The major rose pests in our area are aphids, thrips, and powdery mildew. Some rosarians rely heavily on pesticides. However, I recommend that some level of insect damage be tolerated. Aphids can be knocked back with soap sprays or high-pressure hose. Flower thrips are tiny, winged Insects about 1/20 inch long. They affect the buds and blossoms of roses and some other flowers. Thrips are said to prefer light-colored blossoms, such as yellow and white. Their damage can readily be seen as discoloration of the petals. During severe infestations, some blooms will not open normally due to the insect's damage. Sometimes, a concentrated effort of misting the buds and blossoms with an insecticide such as acephate is necessary. Powdery mildew is a fungus. Symptoms include a whitish coating on leaves and young shoots, curled leaves and distorted buds. This disease is best controlled by planting resistant varieties or a preventive fungicide spray. Overhead sprinkling may actually reduce the spread of powdery mildew because it washes spores off the plant; also, if spores land in water, they die. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://ag.arizona.edu/yavapai/anr/hort/byg/. |