Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
6/18/01
Contacts:
Cindy Haynes, Horticulture Extension, (515) 294-4006,
chaynes@iastate.edu
Elaine Edwards, Continuing Education and Communication
Services, (515) 294-5168, eedwards@iastate.edu
Yard and Garden Column for the Week Beginning June 22
Caring for Roses in the Summer
By Cindy Haynes
Extension horticulturist
Iowa State University Extension
Roses are one of the most popular flowers in the summer garden. In fact, they are probably the most recognized plant worldwide. Hybrid tea roses, those roses most noted for their regal blooms, will bloom throughout the summer months. Blooms from cultivars like 'Peace,' 'Mr. Lincoln' and thousands of others are used as cut flowers by florists and gardeners everywhere. But there is a price to pay for a summer full of roses. Producing healthy plants with beautiful blooms requires routine maintenance and a regular diet of water, fertilizer and pesticides.
Watering
Roses require approximately 1 inch of water per week for optimum performance. Unfortunately, Mother Nature doesn't always cooperate. During dry weather, roses should be deeply watered once a week. Mulching helps conserve moisture and eliminates weeds that compete for water resources. When watering roses, water in the morning and avoid wetting the leaves. By keeping the foliage dry, you will help prevent or reduce the incidence of disease.
Fertilization
Roses are heavy feeders. They require regular fertilization to remain healthy and vigorous. Even with highly organic, fertile and well-drained soils, fertilizers are commonly applied two or three times during the growing season. Any complete fertilizer like 10-10-10 or 5-10-5 will work. The first application is usually made in early spring immediately after pruning. A second application can be made during the first bloom period. The final application should be made in mid to late July. Late applications of fertilizers should be avoided. Fertilizing after the end of July promotes new growth that may not have time to harden sufficiently before winter.
Disease and Insect control
Roses were bred for their colorful and fragrant blooms; many were not bred for their tolerance to disease or insects. This means that regular sprays of fungicides, insecticides and miticides are often necessary to produce state-fair quality rose buds.
Black spot and powdery mildew are the two most common diseases of roses. Black spot is recognized by the appearance of dark spots on the leaves. Leaves eventually turn yellow and later drop off completely. Plants affected by powdery mildew will have a whitish coating on the leaves. Removal of infected leaves may help control the spread of both diseases if caught early. For best control, fungicide sprays are often used as a preventive treatment. These sprays must be applied regularly throughout the growing season.
Mites, tiny arachnids found on the undersides of leaves, are a common pest on roses. If caught early, a forceful spray of water can help control mites. Otherwise, miticides or pesticides specifically for mites, are required. Another common pest is the leaf cutter bee. This small bee cuts circular disks out of the rose leaves. The bee uses these disks in building its nest. While the resulting "holey" foliage is unsightly, no real damage occurs to the plant. Therefore, sprays to control this beneficial insect are not recommended. Other potential rose pests include rose slugs, aphids and thrips.
Fortunately, many garden centers sell all-purpose rose care products that contain both a fungicide and an insecticide. These multi-purpose products can be used throughout the growing season to prevent outbreaks of a wide range of rose pests. Check label directions for application rates and scheduling of sprays.
Deadheading
Deadheading is the process of removing spent or old flowers as they fade. This process conserves energy that the plant would normally use for seed production. Instead of producing seed, the plant produces additional flowers.
If deadheading is done correctly, you will have a constant supply of buds ready for vases. When deadheading a rose, leave plenty of foliage on the plant for the production of new blooms. Ideally, at least two sets of five-leaflet leaves should remain on the stem of the plant after cutting or deadheading roses. To aid plant establishment, remove the faded flowers on recently planted roses above the uppermost three-leaflet leaf.
Is all this work worth it?
Only you can answer this question. Growing hybrid tea roses requires a commitment of time and money from Iowa gardeners. Yet the rewards when all is said and done can be armloads of fragrant and beautiful blooms. Why not talk your neighbor into growing them and giving you a few flowers?
ml: isugarden
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