A Rose Primer
From Basic Rose Growing in Tidewater, Virginia by Master Gardeners Leslie Bowie, Gloucester; Lisa Broudy, Newport News; Jan Spencer, Hampton.
This information attempts to focus on growing roses in the Tidewater and surrounding areas and the problems most generally encountered in our unique environment. Just as the climate and conditions in Tidewater are different from the climate and conditions in other parts of Virginia, so are the conditions from backyard to backyard. One of the joys of gardening is learning to observe nature closely. As you become familiar with your roses, you will learn what works best in your garden. Plant your roses, care for your garden, but most of all enjoy!
Rose plants should be purchased from reputable sources. Generally, local nurseries and garden centers, and mail-order nurseries are good sources. You can purchase dormant, bare-root roses in the early spring and potted roses later in the season. Roses are usually sold in 3 grades: #1, #1 1/2, and #2. Number 1 grade is the largest and more vigorous with at least 3 canes.
Roses grow best in full sunshine, but will tolerate a minimum of 6 hours. Morning sun is preferable because it will help dry the dew on the leaves, thus discouraging the development of fungal diseases. Good air circulation also helps discourage diseases, so it is not usually advisable to plant too close to walls, buildings, hedges, nor near trees or large shrubs which may compete for moisture and soil nutrients. Good soil drainage is a must.
Roses can be grown successfully in a wide range of soil types. Soils that are too heavy or too light can both be improved by adding organic matter such as peat moss, leaf mold, compost or aged manure. The optimum pH range for roses is between 6.5 and 7.0, which is lightly acidic. If you have not tested your soil in the past 3 years, your Extension Office can provide you with soil sample boxes to send to the Soil Testing Lab at Virginia Tech. You will receive instructions on how to correct any deficiencies. Because Tidewater soil is typically acidic, agricultural lime is usually recommended to raise the pH. (It can safely be applied at the rate of 2-3 lbs. per 100 sq. ft., although a soil test really should be done.) Other soil amendments, such as superphosphate or bone meal may also be worked into the upper 6" to 8" of the soil, at the rate of 5 to 10 lbs. per 100 sq. ft. No additional fertilization is needed for newly planted bushes until after the first bloom cycle.
Individual planting holes 18" wide and no deeper than 12" may be dug if only a few roses are to be planted. If a number of roses are to be planted in a continuous area, prepare the whole bed by spading the soil to about 12", (amending as described above), then dig planting holes within the prepared bed. Bare-root roses should be planted according to the instructions that come with the plants immediately after you get them. When planting a bare-root rose, make a small cone of soil in the center of the hole and set the plant on the peak of the cone so the roots spread down its slopes. The bud union should be slightly above ground level. Fill the hole 3/4 full of soil, the soak with water. After the water has drained, finish filling the hole with soil. Container-grown plants may be planted from spring to fall--whenever they are available. Remove the plant from the container ad place it in the hole so that the soil level is even with level of the surrounding bed. Work soil around the plant as necessary so that no air pockets remain. Water well. Space hybrid teas 2-3 ft. apart; grandifloras 3-4 ft.; floribundas and polyanthas 2-2 1/2 ft; miniature 1 1/2-2 ft. apart. Climbers should be spaced 6-8 ft. apart.
Roses require plenty of water (at least one inch per week) to assure even, steady growth. Water at ground level to avoid wet foliage which encourages the spread of disease. Remember to water before spraying or fertilizing and especially during dry spells, even in the winter.
Pine straw, newsprint (not colors), shredded leaves, peanut hulls, aged compost, or almost any loose organic material can be used as mulch. It is used to hold moisture, control weed, protect the bush, and give a finished look to the bed. Spread 2" to 3" of mulching material evenly around and between the plants. As the mulch decays and becomes incorporated into the soil, add new material. In winter, blanket the bud union with a very loose covering of mulch to protect the plant from drying winter winds. Uncover the bud union when all danger of frost has past.
Fertilizing Established Plants
Properly sustained nutrition insures healthy, vigorous growth, and disease-resistant plants. Fertilizers are classified as organic or inorganic (chemical). Organic fertilizers, such as aged manure, compost, fish emulsion, bone meal, leaf mold, etc., add many nutrients not found in chemical fertilizers. Organic fertilizers can be applied on a regular basis at any time during the growing season as their nutrients are released slowly.
Inorganic fertilizers, such as 10-10-10 or 5-10-5 in granule form are applied by spreading around the base of the plant and working into the soil at the rate of 1/2 cup to 1 cup for each plant. Liquid fertilizers, or soluble powders mixed with water, can be applied directly into the ground as per label directions.
It is a good idea to alternate organic and inorganic. The plant does not necessarily know the difference, but the soil will appreciate the long-term benefits of the addition of organic materials. Unless you plan to exhibit, your roses need only a regular monthly feeding from March through October. Although they may continue to bloom into the winter, do not continue fertilizing.
Roses will give you lovely blooms all summer long, year after year, if they are healthy. When the plants are stressed they turn their energy toward survival rather than beauty. Buy healthy plants. Reject those with abnormal swelling or discoloration on the canes or roots. If your rose bushes are planted out in the lawn instead of a bed, mulch for weed control. Do not run lawnmowers and weed eaters up against the canes as a damaged cane is an open door for pests and diseases. Avoid long intervals between watering. Have a neighbor water your roses while you are on vacation.
Keep the area around the bush clean and free of dead and diseased leaves and branches. (Do not put the debris in the compost pile.) Inspect your plants often and act as soon as you see a problem. Prune out any canes with cankers, discoloration, or sunken areas, cutting 1 or 2 inches below the infected area. Dip shears in a solution of rubbing alcohol or household bleach and water at a ration of 1 to 10, before moving to the next bush. If diseases or insects become a problem, use only those pesticides recommended by your Extension Office for specific problems and follow the directions exactly when mixing and applying chemicals.
The most common diseases are powdery mildew and black spot. Caused by fungi, they can be controlled with fungicides, but rarely eliminated entirely.
Powdery mildew occurs most commonly in spring and autumn when the days are warm and the nights cool. The leaves, buds and stems are covered with white or gray powdery coating. New growth may be stunted and curled and may drop off. The buds are malformed and fail to open.
Black spot is most prevalent when moisture remains on the leaves from overhead watering, long rainy periods, or heavy dew. The fungus over-winters in the canes and on infected leaves and reappears on otherwise vigorously growing plants in the spring and summer. Complete defoliation may even occur on susceptible varieties. Black spot looks just like the name implies--black spots (sometimes surrounded with yellow) on the leaves grow in size until the leaves drop off. When on the canes, the spots are reddish-purple.
For black spot and mildew, spray both the top and undersides of the leaves as soon as they appear in spring with the recommended fungicides. Continue spraying every 7 to 10 days throughout the growing season.
Another fungus disease, Botrytis blight, occurs during long periods of frequent showers. The flower bud fails to open and the interior of the bud is usually filled with a cob-webby mold. Control is just to cut all infected buds along with several inches of stem and remove from the garden. Other diseases that can affect roses are mosaic, stem canker, and crown gall. They are not usually a problem in clean beds where sanitation is practiced and no fallen debris is allowed to remain. If you suspect a problem with your roses that is not powdery mildew or black spot, call your Extension agent.
Roses are attacked by many insects. The most common in this area are described below. Remember when using pesticides that they are nondiscriminatory, killing even the "good bugs", so learn to identify specific insects and use only recommended pest management for them. Experiment with companion plantings and natural predators. While enjoying your evening walk in the rose garden, be on the lookout for problems and act early.
- Japanese beetles. The Japanese beetle attacks rose flowers and foliage during July and August. This beetle is about 3/8" long with metallic green and coppery-brown wing covers. Japanese beetles can be successfully controlled by commercial traps placed away from the garden to attract beetles away from the roses. Treating your yard and garden in early spring for grubs will help to keep the mature beetle population down during the summer months. If only a few are seen, just hand-pick and destroy.
- Aphids. Several species of aphids occur on stems, leaves, and buds and often occur in large numbers. By sucking the plant juices, they stunt the plants. Consult your local Extension Office for both chemical and nonchemical control.
- Rose Stem Borers. A hole in the end of a rose cane or stem probably indicates the presence of a borer which has burrowed down deep into the stem tissue. Infested stems usually die back and the entire plant can be lost if borers are not controlled. Cut and destroy infested stems, then seal the fresh cut with white glue. Make a habit of sealing the ends of stems whenever you gut flowers to bring into the house or prune.
- Leaf-Cutter Bees. Leaf-cutter bees cut out circular pieces from rose leaves and other plants and save them as food for their young in burrows dug in the pith of rose stems, broken branches, or in plant crevices. The tunneled stems usually die back for several inches. No satisfactory insecticide control is available for these bees, which are valuable as pollinators. Sealing the ends of the canes prevents the bees from entering and tunneling the stems.
- Spider Mites. The two-spotted spider mite and related species such the juices from rose leaves, which soon become stippled. As the injury progresses, the leaves turn brown, curl, and drop off. When mites are abundant, they spin a web over the leaf surface. These mites are almost too small to see without magnification, but if you suspect mites, hold a plain white sheet of paper under the leaves and tap gingerly on the leaf a few times and you should be able to see minute red specks of the paper. Infestations usually occur in hot, dry weather, but can be controlled by drenching the undersides of the leaves every several days with a forceful spray of water from a hose-end nozzle of water wand.