We have “many” knockout roses. With the exception of one, which has no new growth coming out of bottom, and pretty sure it’s dead, all the others have growth coming from the bottom of plant. They were prunedin the fall, but perhaps not enough. Should we. Prune them again hoping the new growth will fill in the bush. We love these bushes and will do what we can to save them. Thank you for your time.
Wayne County Michigan
Anything not leafed-out yet is dead and can be pruned off. The new growth coming up may take two seasons to reach the shrubs previous size. For your future pruning follow the guidelines from University Extension and the Knock Out rose website:
Do not trim or prune roses after Mid August. This allows time for tender growth to ‘harden-off’ and is more likely to survive winter. Trim or prune Knockout roses from late winter to when the buds begin swell in spring. Dead, diseased or damaged branches can be removed anytime. Here is the general guide to pruning shrub roses from Extension—-
“The best time to prune roses is in late winter or early spring just before growth begins, typically early March through early April. Pruning needs to be done every year and should be followed by deadheading and clean-up throughout the growing season. Steps in Pruning • Remove dead, diseased, or damaged canes. Cut stems 1 inch below darkened areas, cutting back to green wood (the center of the stem will be white, not tan). Make the cut at a 45-degree angle, 1/4 inch above an outward facing bud. Remove canes that are growing toward the center of the plant, as well as any crossing canes. Old, shrub, and species roses should be pruned lightly, removing no more than a third of the growth.”
And this instruction comes from the FAQ SECTION OF KNOCKOUTROSES.COM——
“In the spring, after the last threat of frost has passed, cut back your roses (using hedge loppers) to about 12". This should make them grow to about 3'-4' tall by the end of the season.”
And another extension article recommends this pruning—-
“Since Knock Out® roses only reach a maximum height of 4 feet and a width of about the same they do not require much pruning. Simply cut the canes back every year in late winter or early spring to approximately 24 inches. Cutting them back very severely, like a hybrid tea rose is not recommended. They won’t die but will require a long time to recover. Periodically, older, declining, and broken canes will need to be removed. This can be done at any time of the year.”
So, there is a range of 12-24 inches for how far back you should prune. Some gardeners let them reach their mature height and just trim the rose hips off in spring. Any dead canes should be removed as close to the base as you can.
Last fall it was warm until late in the season followed by a sudden freeze. Many plants did not have time to harden off for the winter. You may have seen the result of this on some maples, and other trees and shrubs, which retained their dead leaves over the winter without dropping them. This was also hard on many other perennials and possibly is why you lost one of your knockout roses.
Thank you for using our service.