Abnormal Rose Cane Growth

Symptoms

• Afflicted rose bush canes develop a spiral growth habit with leaves spaced closer together along the stem. New shoots have a red tint and grow more quickly than normal. The new leaves also have a red tint. Small shoots are clustered together at the tops of stems, a condition known as witches broom. The shrub produces smaller, distorted leaves and an unusually high number of thorns. If the shrub blooms, the buds and flowers are deformed and discolored.

Herbicides

• Herbicides containing glyphosate or a growth regulator can cause abnormal cane growth as well as witches broom. They can also kill rose bushes. If herbicides have been used around the rose bush recently, they may have damaged the canes and caused the abnormal growth.

Disease

• The disease that causes the abnormal cane growth is known as rose rosette disease. Nearly microscopic-sized mites spread this virus from rose to rose. They crawl from rose to rose where the leaves or canes of neighboring bushes touch. Insects will carry them from rose to rose and they can be carried on the wind. The virus lives in the bush and the soil around it. Multiflora roses (Rosa multiflora) are highly susceptible, grow wild and serve as host to this disease. They are hardy in U.S. Department of Agriculture hardiness zones 5 to 9, just like most cultivated roses.

Treatment

• When an herbicide has caused the abnormal cane growth, the rose will usually recover. Watch it closely for a few weeks. With good care, new canes, stems, foliage and flowers will be healthy. If the rose has contracted rose rosette disease, sadly there is no cure. It will continue to decline until it dies. To help prevent further spread of the mites and disease, remove the bush from the property. First contain the mites by covering the rosebush with a garbage bag. Dig up the bush along with roots and surrounding soil. If multiflora roses are growing within 100 yards of the rose garden, remove and destroy them if possible. Otherwise, do not plant roses downwind of them.