Tips for pruning Knock Out roses include cutting them back in the early spring and shaping them as needed during the growing season. This rose variety doesn't require deadheading, and still looks beautiful even with mild pruning, states Today's Homeowner.
To ensure the roses have the most appealing shape and the best flowers in the summer, prune them heavily in early spring before they start to grow. Cut out up to a third of the bush's height to promote re-growth of thick, healthy canes with ample buds.
During the summer growing season, trim Knock Out roses as needed to help the bush keep its desired shape. Because these roses can grow rapidly, this trim is necessary to keep a structured shape; however, to keep a more natural shape, skipping the summer trim is also an option.
Deadheading Knock Out rose bushes can help extend their flowering and promote healthier, more vibrant roses. Twist off the spent flowers as often as once a week or as infrequently as once a month. Even without this mild pruning, the Knock Out variety of rose still produces colorful flowers with blooms emerging in the spring and lasting into the fall. If a bush is not blooming to expectations, increased frequency of watering and feeding may help.