Basic care of roses essential for garden success

Roses are criticized for being the “diva” or prima donna of the garden because they are delicate or temperamental. Many roses are highly susceptible to disease and insects but knowing how to care for them is the key to your success.

First, make sure you have planted your roses in the right place. Roses grow best in full sun (at least six hours). They require good, well-drained soil with a pH between 6.0 and 6.5. To check for drainage, dig a hole 2 to 3 feet deep and fill with water; the hole should empty in a few hours.

Plant floribundas and hybrid tea roses 2 to 3 feet apart. Climbers and most shrub roses should be planted 4 to 8 feet apart. The plant holes should be 18 inches in diameter and 12 to 18 inches deep.

Roses require evenly moist soil. Apply water slowly to prevent surface runoff and ensure deep soil penetration. The soil should be soaked to a depth of at least 1 foot. Wet foliage promotes the spread of diseases so try to keep the foliage dry while watering at the base.

Roses are hungry plants and need fertilization for best performance. Inorganic fertilizers are quicker acting and more concentrated. The first application of fertilizer should be given in spring after new growth and repeated every six weeks. Stop fertilizing six to eight weeks before the first average frost date in your area. This prevents the plant from producing large amounts of new soft growth late in the summer.

Pruning plays an important role in the proper care of your roses. Pruning helps correct, adjust and modify the size and shape of the plant. Generally, the best time to prune is after the frost has gone.

When pruned, roses will generally take 75 to 80 days to bloom. When pruning, remove all dead, diseased, broken or injured wood, as well as suckers that are different from the main plant. Remove branches that cross through the center of the plant or rub on other branches.

Prune to improve the shape of the plant and to allow for good air movement through and around the plant. Make smooth, clean cuts slightly above a strong bud that faces the outside of the plant.

The most important technique to master in pruning roses is the correct angle and direction of the cut. Make sure your tool is sharp. The cut should be at a 45-degree angle about one-quarter inch above a bud eye. The cut should angle away from the side of the eye so that the sap that rises to the top drips down the other side. Choose an eye on the outside of the cane to encourage new outward growth, opening the plant for circulation.

After pruning, clear the ground of dead leaves and debris to reduce hiding places for insects and fungi.

Rose disease can be controlled with a regular spray program. Remember to spray both the upper and lower leaf surfaces. Liquid sprays are more effective than dusts.

The most common and serious disease is black spot, which appears as black spots with fringed margins on the leaves. Black spot weakens the plant and reduces flowering. The spots enlarge as they develop until the leaf yellows and finally drops off.

The fungus overwinters on fallen leaves and dead canes and affects only roses. Infections can reoccur several times each summer. Wet leaves are essential for its spread. The infection is worse in wet, humid and hot seasons. Prevention includes good air circulation, proper pruning, disposal of dead material, avoiding wet foliage, and fungicide control.

Mildew is another disease that affects roses. This appears as a grayish, powdery growth on leaves, especially young leaves, and their tips. It thrives in high humidity. It occurs more frequently on roses that are close to ponds, streams or other damp areas. Leaves become deformed and crumpled. Ramblers are highly susceptible. Fungicides provide a good control of the disease.

Brown canker is a less serious disease than black spot or mildew but very destructive. It appears as a small purple-tinged or white spot that develops into large brown patches. The canes will grow poorly or die. This occurs mostly in the summer. Canker is controlled by cutting out the infected canes as soon as you notice this disease. You will need to cut out the affected canes well below the lowest point of infection.

Roses can also be affected by insects. Aphids are the most common pest of roses. They are soft-bodied, green, brown or reddish and found in soft growing tips and on stems immediately below flower buds. In severe cases, they will deform the leaves, stems or buds. Aphids can be controlled by insecticides beginning in spring. If you have an extreme case, spray every four days.

Red spider mites are not as common as aphids and more difficult to detect and control. Mites are very small, hardly visible to the naked eye. If you have mites, you will notice tiny webs between veins on the lower sides of leaves. The leaves become yellowish and finally turn brown. Mites are prevalent in hot, dry weather. Miticide must be used frequently to rid the roses of this disease.

Taking care of your roses will be worth the reward as they flourish and bloom through the summer months bringing you the beauty and fragrance they are known for.

For questions on this subject or any gardening topic call the Master Gardener Helpline: In New Castle County, 302-831-8862; in Kent County, 302-730-4000; and in Sussex County, 302-831-3389.

For information about master gardener workshops, visit udel.edu/master-gardeners and click on Gardener Workshops.