Keep Roses Blooming All Summer

Work to produce repeat-flowering roses only began to receive attention in the early 1800's, and it was only in the mid-1800's that the first hybrid tea and hybrid perpetual roses where developed. The repeat-blooming character of these early roses was not as dependable as in modern roses. Culture and climate could influence the number of times that a rose plant would flower during the summer.

Even today, with very dependable repeat-blooming types, proper culture is important if plants are to produce a maximum amount of blooms throughout the summer. Good weed control is very important for summer rose care. Weeds not only compete for light, water and nutrients but may slow drying of dew and rain from the foliage, thereby increasing the possibility of disease.

Weeds also may harbor insects. Prompt, shallow cultivation is best for removing weeds. Roses respond well to a thick mulch which also is excellent for reducing a weed problem. Keep the mulch thin around the plant stems, but pile it several inches thick between plants. Roses are heavy feeders, so fertilization about every six weeks is necessary. Generally, about one heaping tablespoons of a complete fertilizer such as a 5-10-5 or 4-12-4 provides adequate fertilization for each plant.

If organic forms of fertilizer are preferred, blood meal and bone meal may be used. Apply about one tablespoon of each per plant. Do not fertilize roses after July. Late summer and fall fertilization promotes tender growth more susceptible to winter damage. Always scatter fertilizer on the soil surface and work in lightly.

Faded flowers should be cut promptly when bloom is finished. This not only improves appearance but prevents seed formation or the development of petal blight. At least two large, healthy leaves should remain on any stem from which a flower has been cut. Generally, unless stems are needed for arranging the flowers, the plant should be allowed to retain as many leaves as possible when flowers are cut.

Ramblers and spring flowering climbers may be severely pruned at this time. Remove all old, flowering canes, and save vigorous young shoots that are developing from the base. If vigorous young shoots are abundant, thin them out, to the best three or four. These shoots will flower more heavily next year if tied in a somewhat horizontal rather than in a vertical position.

Pest control of roses is extremely important for maximum flower production. Black spot is usually the biggest disease problem. Pick off infected leaves to reduce spread if only a few are present. A regular spray, however, is usually necessary to control the disease. Folpet (Phaltan) and benomyl (Benlate) are two materials that are effective in controlling the disease. Spray either at weekly to 10-day intervals. A rotation of these two chemicals provides good control. When possible, spray as soon as possible after rainy periods. Keep a close watch for the development of other problems and apply controls promptly. Prompt treatment often requires less chemical and less time and is more effective.

http://www.ipm.iastate.edu/ipm/hortnews/1991/5-22-1991/roses.html