To maintain a size of 3–4’ w x 3–4’ h, Knock Out Roses should be cut back once a year to 12” high. Check your rose bush from time to time in late winter/early spring, and when you start to see new shoots growing from the canes on your rose bush, that’s a good sign that it’s time to prune.
Mar 01, Depending on where you live, you can technically cut your knock outs back anytime, but I recommend doing a drastic prune in late winter/early spring. Have you pruned them lately? For the health of the plant you should prune it back by 1/3 to 1/treemulch.buzzted Reading Time: 4 mins. Jan 08, You can prune once a year and then trim and cut when you feel the need Proper Pruning Knockout roses are such hardy plants that any way you prune, they survive and thrive!Estimated Reading Time: 4 mins.
Jan 13, Research indicates that Knock Out roses respond best if not cut back lower that 24 inches for the hard pruning in early spring, and more moderately in the fall. I’m surprised they have done well cut back as short as 12 inches from the treemulch.buzzted Reading Time: 6 mins.