Fall and winter rose care

By John Fulton

[November 29, 2012]  Many of the roses that are classified as old garden roses are extremely tolerant of cold temperatures, while others like hybrid teas experience considerable damage. Also, budded roses stand a greater chance of injury or death due to severe cold than do own-root roses. When selecting roses, always select cultivars that are able to tolerate the coldest temperatures in your area, based on USDA hardiness zone maps.

One of the ways to protect roses for the winter is to be sure they go completely dormant. To accomplish this, stop fertilizing early enough so growth slows down. No fertilizer should be applied after Aug. 15. To further encourage dormancy, stop deadheading or cutting flowers after Oct. 1 and allow the plant to form hips.

There are many methods to provide winter protection for roses. The whole idea of winter protection is to keep the plant uniformly cold and frozen all winter and prevent the damaging effects of alternate freezing and thawing. Whatever the method, don't begin covering plants too early. Wait until a hard, killing frost has caused most of the leaves to fall, and the temperature has dropped into the teens for several nights. Prior to covering, remove any foliage or other debris that might harbor disease for the next season.

Before covering, some tall roses may need minor pruning to reduce their height, and tie canes together to prevent wind-whipping. Pruning at this point should be kept to a minimum. Most pruning will be done in the spring to remove dead and diseased canes.

The most common way to provide winter protection is to pile or "hill-up" a loose mix of soil and compost around and over the plant, about 10-12 inches deep. A variety of hilling materials can be used, but the key is to be sure the material is well drained. Wet and cold is far more damaging than dry and cold. Soil that is used to hill-up plants should be brought in from outside the rose garden. After the soil mound has frozen, the mound can be covered with evergreen boughs, hardwood leaves or straw to help insulate and keep the soil frozen.

A variation of the hilling method is one using collars. An 18-inch-high circle of hardware cloth or chicken wire is placed around the plant. The collar is filled with soil, allowed to freeze, then mulched with straw. The benefit of the collar is that it holds the soil in place all winter and prevents it from being washed or eroded away.

Another popular method of winter protection for roses is the use of plastic foam rose cones. If these are used, they need to be used properly. First, don't cover the plants too early. Follow the general timing guidelines. Second, cones need to be well ventilated by cutting holes around the top and bottom of the cones. This helps prevent heat buildup on the inside during sunny winter days. It is also advisable to mound soil around the crown of the plant before putting the cone in place. For extremely tender varieties, some rose growers cut the top off the cone and stuff it full of straw for added protection. It is also a good idea to weight the cone down with a brick or stone to keep it from blowing away.

Climbing roses offer more challenges. For marginal varieties, climbers may need to be removed from their supports and bent to the ground, then covered with 6 inches of soil and mulched. When laying climbers on the ground for covering, one needs to be very careful not to injure or crack the stems. As the weather gets colder, their long stems are more rigid and they are easily broken.

Another method that can be used is to physically pack straw around the canes while they are still attached to the trellis or support. The straw is held in place with twine to keep it in place over the winter.

Generally knockout roses don't require special care in hardiness zone 5 or south. We are in zone 5b. If you do want to do something because of prior problems, you can mulch the crown area. Some go to the extreme and burlap them or put wire around them and fill with leaves, but that is entirely up to you. The basic care is a pruning, if needed, in the early spring to size or shape.

[By JOHN FULTON, University of Illinois Extension]