Roses grown in Colorado generally suffer from some dieback during cold, windy, dry winters. To help with plant vigor and health, prune roses back to healthy wood during the last week of April or early in May. Because of winter dieback this may mean removing a significant portion of the shrub.
One of the most important things when doing any pruning is using the proper tools and keeping them sharp. It’s recommended that you use a bypass or scissor-type pruning shears for clean cuts. This will help the plant seal over wounds more quickly.
Before pruning examine each cane individually. Making your pruning cut at an angle, one-eighth of an inch above a healthy bud, prune out any discolored stems. Ideally, the bud should be located on the outside of the stem so that new growth will be well spaced, creating a more shapely shrub with good air circulation. Buds will be slightly swollen and red in color. Healthy canes are green with yellow-green piths. Dead canes should be removed completely to the ground. Also remove any suckers or new growth arising from the rootstock at the base of the plant.
If rose cane borer is a problem in your roses — you may notice tunnels in the canes or small, sparse, yellow or wilted leaves — consider dabbing each pruning wound with white glue or clear fingernail polish, which will prevent borers from entering canes.
Mounds of soil that you placed at the base of roses for winter protection can also be removed at this time. Every few days, gradually remove the mound a few inches, which will harden off new sprouts to outside temperatures and sunlight. Take care not to injure any new sprouts when removing the mound. By removing the entire mound at once, the light and temperatures may be too extreme for the young sprouts and likely will injure or kill them.
Alison Stoven is a horticulture agent for Colorado State University Extension in Larimer County.
