Pruning Knockout Roses
Prune roses in spring, never in the fall. When the forsythia blooms yellow, it’s time to prune the roses.
No forsythia in the neighborhood?
In that case, when you see new sprouts on the rose stems, get out the pruners. Make sure to wear thick gloves to avoid the sharp thorns.
You can use pruners cutting one stem at a time, but it’s much quicker and easier to use hedge shears. Cut back to one-third of the mature size. The plant will triple its size during the growing season. So if a shrub finishes the season at three and a half feet, cut it back to a little over a foot into a rounded shape that is pleasing to the eye. There is no need to be careful and meticulous. Just whack away to trim it to one-third of its size.
Clean up the debris around and under the shrub to deter mold and mildew later in the season. Planting where there is good air circulation and plenty of sunlight, cleaning up old leaves, and in summer spraying leaves with a disease control product will do a lot to deter black spot and powdery mildew.
Pruning in the spring promotes healthy growth and lots of blooms. Pruning in the fall may lead to frost damage in the spring. Leaving the stems taller results in larger but fewer blooms. Pruning the shrub shorter gives you smaller but many more blooms.
Knockouts are easy to grow, keep on blooming until a hard frost without any deadheading, and are more resistant to disease than traditional roses.
Enjoy your beautiful roses!
This information is especially for the popular Knockout roses but is the easiest method for nearly all roses.