By James Feucht, Ph.D., Colorado State University Landscape Plants Specialist
December's freeze was anything but good news for Colorado's rose bushes.
The freeze killed a lot of roses almost to the ground. This is the time of year, however, to begin bringing those bushes back to health.
During the last week of April or the first week of May, prune roses back to healthy wood. This may mean most of the plant's top portion will be removed.
If you mounded your roses last fall, you now can gradually remove the mound a few inches every few days. Gradual removal of the mound accustoms the sprouts to bright sunlight and cooler temperatures. Take care not to break any soft sprouts developing in the mound. If you remove the mound all at once in early May, younger shoots may die, particularly if the weather is warm, bright and sunny.
To prune, examine canes carefully and remove discolored portions. Make the pruning cut about one-eighth inch above a healthy bud. If possible, cut to a bud that faces outward. This ensures adequate spacing between canes and results in an evenly shaped bush.
To prevent rose cane borer, treat the cut ends of the cane with pruning paint sold for this purpose. You also can use orange shellac or clear fingernail polish.
Climber roses, depending upon the variety, also appear to have suffered severe freeze damage. Normally, you'd prune at this time of year to remove entire surplus canes. This year, however, you may need to prune to the ground. Because this type of rose produces flowers on last year's wood, such pruning will mean no flowers this year.
Some climber roses have frozen below the graft union. In this case, you may need to replace the plant. Examine the color of the canes to determine the damage. Frozen tissue is dark brown beneath the bark when you scrape with your fingernail. These canes may be dead to the roots; roots also may be mushy and dark colored.
A healthy cane is green on the surface and a lighter-to-yellowish green beneath the bark. Healthy canes also have small reddish buds where leaves were attached last year.
This also is the right time to assess winter damage to privet, pyracantha (firethorn), euonymus and similar broad-leaved evergreens. New growth, or at least bud swelling, should be apparent now. Remove all growth above healthy, swelling buds. If canes are brown and roots are developing a mushy texture, chances are the whole plant is dead.
For more information about spring-time care of perennials, contact your local office of Colorado State University Cooperative Extension.
Photograph courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010