Knockout roses are a group of hybrid shrub roses bred for wide climate tolerance and significant resistance to disease and insect pests. Unlike traditional rose pruning, Knockout rose shrubs perform better when sheared down each year in the spring. They are also self-cleaning so they do not require dead heading, which adds to their low maintenance.
Pruning Knockout roses should be done once a year in the early spring or after the last hard frost has passed in your region. Even significant or harsh pruning in the early spring will not inhibit bloom in the current year. Knockout shrubs will easily rebound from their spring pruning with prolific bloom in the late spring, summer and fall until the first hard frost occurs.
Annual pruning of Knockout roses is most easily done with a clean and sharp pair of long-blade scissor shears or loppers. Unlike traditional rose pruning that requires cane by cane cuts, Knockout roses neither require nor perform well with this style of pruning. Lopping off up to one-third of the rose shrub volume and bringing the height down to between one and two feet over the crown of the plant is ideal. Make a flat-top cut with the tool blades held parallel to the shrub top. Clearing up all of the clippings and debris from the soil surface will help to keep disease and pests from establishing themselves and leave a clean surface for fertilizer and mulch applications.