Pruning is best done right when the leaves are opening. If you missed that timeframe, it is OK to do it now. However, there is no need to cut Knock-Outs back by one third. Remove thick, gray canes to the ground. Remove dead wood, wood that is growing toward the center instead of outward and any canes that are less than pencil width. The goals are to increase vigor by removing old wood and to improve air circulation and sun penetration which lessens disease and improves bloom.
Answered on April 25, 2018
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