Culture of garden roses
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Roses are one of the most popular garden flowers. They can be grown in all parts of Minnesota. Shrub and old-fashioned roses are useful in landscape plantings around the home. Selected shrub roses are more disease resistant and may require less winter protection than hybrid tea roses. Climbers are effective when grown on an arbor or fence. The hybrid teas, floribundas, miniatures, and grandifloras are the focus of this fact sheet and require special culture and are best planted in specially prepared beds.
Selecting a site
Roses do best where they receive a minimum of four-to-six hours of direct sunlight daily. Roses prefer a well-drained, fertile, loamy soil at least two feet deep. Air movement through the foliage is desirable to keep it dry. Foliage that is moist for long periods is likely to become infected by disease organisms.
Selecting and purchasing roses
Before you buy rose plants, decide where you want to use them and acquaint yourself with the many different classes of roses. There are hundreds of named rose varieties from which to choose.
You can learn much by studying rose catalogs. A visit to local rose gardens also provides an excellent opportunity to study roses and learn which ones are adapted to your area.
You may purchase roses as dormant plants. When ordering them, indicate that you want number one plants. They are large plants that quickly recover and provide abundant bloom the first year after planting. Request delivery between April 15 and May 15. If you select dormant plants from a local nursery, avoid plants with long sprouts, as they deplete a plant's food reserve. Plants should have at least three strong canes. They should have moist moss around their roots and be wrapped in waterproof material.
You can plant potted roses later in the spring than dormant plants. However, since their foliage is tender, do not plant them until all danger from frost has passed.
A properly planted rose bush
Plant dormant roses in early spring. Bare root plants should be presoaked in water for 24 hours. Plant them with the bud union (knob) an inch below the surface of the ground. The hole should be large enough to permit spreading out the roots without bunching them. Spread the roots in the hole and pack soil under, around, and over them. Water the plant thoroughly.
Mound the base of the plant with six inches of soil after you water it. Keep the mound moist and leave it in place for about 10 days or until growth has started. Check it periodically to see if growth has started. Remove the mound carefully. Preferably, remove it on a cool, humid day rather than on a hot and windy one.
You can plant potted roses in much the same manner. You must remove the pot. Remove the bottom first, place the rose in the hole, and carefully remove the side without disturbing the soil ball. Fill the hole with soil and water the plant thoroughly. It is not necessary to mound actively growing roses.
A constant moisture supply is vital to successful rose culture. Starting in early spring, roses require a minimum of one inch of water per week. Apply this amount at one time. Sandy soils will require more frequent watering. Overhead watering is desirable in early spring before growth starts. This watering will prevent the canes from drying. After growth has begun, apply the water directly to the soil or water early enough in the day so the foliage will dry before evening. Wet foliage is susceptible to diseases.
Applying well-rotted barnyard manure to rose beds in early spring is one of the best methods of fertilizing roses. This rotted manure adds both nutrients and organic matter to the soil. Dehydrated manure, bonemeal, and soybean meal also are good fertilizers. Because these materials decompose slowly, you should supplement them with an all purpose fertilizer or with one of the many available rose fertilizers. A fertilizer with a chemical analysis similar to 10-10-10 is desirable. Keep all manure and fertilizers at least six inches from the canes.
You may fertilize roses once monthly until August 1. Be sure you follow the manufacturer's directions. Careless use of fertilizers can be injurious to plants. A thorough watering after fertilization is recommended.
Disease and insect control
Most gardeners prefer a routine spray or dusting program-dusting or spraying every seven to ten days and after rain. Disease problems are most prevalent during periods of moist weather. Use spray materials containing an insecticide, miticide, and fungicide to control insects, diseases, and red spider mites.
Good management practices such as careful disposal of diseased leaves, providing good air circulation and using disease resistant varieties help to suppress insect and disease problems.
To be effective, hand hoeing or cultivation must be started early in the season. Cultivation should be frequent, but shallow.
A summer mulch such as grass clippings, peat, pine needles, wood chips, or shredded bark helps eliminate the unpleasant task of hand hoeing. Place the mulch material at least three inches deep around the plant. A mulch also conserves moisture, cools and conditions the soil. Mulches can be left in place permanently, they eventually decompose and become part of the soil.
Make pruning cut 1/4 inch above an
outgrowing bud at a 45 degree angle
Adequate winter protection is necessary for all roses except those that are completely hardy. Roses must be protected not only against low temperatures, but against fluctuating temperatures.
The two methods described below have been used successfully for protecting tender roses in winter. Spray all the rose bushes with a fungicide to prevent disease organisms from overwintering on plants. And it's a good idea to protect the plants by applying a mouse control bait before you cover them. Styrofoam cones are not good for winter protection.
- Shortly after the middle of October, make a trench extending out from the base of the bush. Make it deep enough to accommodate the plant. You can put more than one bush in a large trench.
- Tie canes together in a bundle and gently tip the bush into the trench. To facilitate tipping, loosen the soil around the plant with a spading fork.
- Cover the plant with the soil from the trench.
- When the ground is slightly frozen, cover the plant with a three-to-five inch layer of leaves. A week later, add a one foot layer of marsh hay.
- In the spring (about April 1), remove all covering in stages as it thaws out. When the ground has thawed, carefully raise the plants, replace the soil around the plants, and water them thoroughly.
- About mid-October, tie the canes together.
- Mound the base of each plant with six-to-eight inches of soil. Place wire netting around the entire bed. Fill this enclosure with about three feet of leaves (preferably oak). Cover the leaves with marsh hay to prevent them from blowing away. Do not cover leaves with plastic, tar paper, or waterproof covering. About April 15, remove the soil mound and water the plants thoroughly.
Remove all deadwood. You may want to shape and cut back some of the tall canes to maintain the planting at a uniform height. When you prune a cane, cut about 1/4 inch above an outgrowing leaf bud at about a 45 degree angle. Cutting at that point helps insure that the plant will be well shaped.