To prune Knock Out roses, remove dead and damaged canes, and cut back about one-third of the plant's height in late winter or early spring. Knock Out bushes that have grown too tall can be cut back to about 1 foot shorter than the desired height.Continue Reading
Use sharp hand pruners to make clean cuts and avoid damage to the stems. Use loppers on canes larger than 1/2 inch in diameter. In warm climates, a second pruning in late August or early September is recommended. During the second pruning, remove any dead canes, and cut back about one-third of the plant's height.
Knock Out roses are fast-growing shrub plants that don't need to be pampered, but pruning them makes for healthier plants that produce more flowers. Knock Out roses drop their old blossoms once the flowers have faded, but occasionally deadheading spent flowers stimulates new clusters of blooms as well as the overall growth of the bush.
Knock Out roses first came to market in 2000 and became popular for their frequent blooming, clusters of showy flowers, dark green foliage, shrub-like growth and disease resistance. They are not immune to disease and may develop black spots, yellowing leaves and powdery mildew, but they usually recover without fungicide treatments. Occasionally, an insecticide may be needed to treat for aphids, Japanese beetles or rose slugs.Learn more about Outdoor Plants & Flowers