Knockout roses are a low maintenance variety of an ever-blooming rose bush developed by Texas A & M University. Knock-out rose bushes have a naturally attractive shape but sometimes they outgrow their space and need to be cut back. Also, suckers can sprout from the ground around the root base and need removal. Suckers are fast growing succulent green limbs that grow taller than the rest of the plant and rarely produce blooms. Wait until the knockout rose bush is planted for two years and cut on the third year if needed, so the plant has time to get established.
Choose a day after the knockout rose bush has produced a flush of blooms and the blooms have faded to cut back your knockout rose bush. Wear eye protection and garden gloves to protect yourself from thorns.
Cut all suckers away from the base of the knockout rose plant using pruning shears. Cut the suckers at or just below ground level.
Stand back and look at the overall shape of the plant with the suckers removed and decide the eventual overall shape. Ideally, the knockout rose should be shaped into a well-rounded garden specimen after pruning.
Shear or prune the knockout rose into shape. If the shape is slightly off when finished don't worry as the plant will quickly recover and you will have another chance. You can cut the knockout rose bush back by as much as one-half its current size without damaging the plant.
Rake the cut branches and leaves away from the pruned knockout rose bush and remove from the garden.