Answer: Late winter or early spring is the best time to prune your older Knock Out roses. Pruning encourages lots of side shoots which will result in a bushy plant. You can prune them back by as much as two thirds and they will respond with healthy new growth when spring arrives.
Your newer Knock Out roses can also be pruned back. Start by removing only part of the long canes. They should send out lateral branches. If all the new growth is concentrated at the tops where you made your pruning cuts, wait until winter or early spring and reduce the length of the canes to the point where you want new growth to start. As the new stems form prune each of them back by a few inches when they reach 8-12 inches. Eventually you'll train your Knock Outs into the right shape and form for your garden. Annual pruning should keep them looking full and bushy.
Best wishes with your plants!
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