Question: I didn’t get a chance to cover my roses before the polar vortex descended. Is it too late? I have a combination of regular roses and shrub roses. C.T.
Answer: Your timing is perfect. Late November to early December is the ideal time to cover cold sensitive roses. Grafted roses, like hybrid teas, grandifloras, and floribundas, need protection from winter cold.
Cut back hybrid teas and grandifloras to 2 ½ to 3 feet. Reducing cane length prevents the canes from catching in the wind, which can rock the plants in the soil causing damage to the root system.
Gradually cover the base of each rose plant with a mound of soil 10 to 12 inches deep. The soil or soil/compost mix should come from another place in the garden, not from around the plant. After the soil freezes, add straw or leaves over the soil mound for additional insulation. The purpose of winter mulching is to keep the soil consistently cold and prevent drying of plant crown and roots.
If you use a styrofoam rose cone, prune the canes back far enough to fit under the cone. Mound soil over the rose crown as described above. Cover the rose with a cone after the soil freezes. Poke holes in the cone so the interior won’t get hot on warm winter days. Anchor the cone by placing a brick or other heavy object on top.
Shrub roses and other hardy roses growing on their own roots require little to no winter protection. Knockout roses are an exception and should be winter mulched with leaves or straw.
Traditional climbing roses usually bloom on the previous year’s growth so the canes must be protected to assure flowers next summer. Take the canes off the trellis and carefully bend them to the ground. Hold the canes down with stakes and cover with several inches of soil. After the soil freezes, cover with straw or leaves. Alternatively, canes can be left on the trellis and encircled with a cylinder of hardware cloth or similar material. Fill the cylinder with clean straw or crinkled leaves to insulate the rose.
Hardy shrub roses with 8 to 10 foot long canes are often grown on a trellis as a substitute for traditional climbers. These roses, such as William Baffin which survived without any dieback in my yard last winter, don’t need winter protection.
Barb Larson is horticulture educator for Kenosha County University of Wisconsin Extension. Barb has a Master’s of Science in horticulture from the University of Wisconsin-Madison. If you have a plant or gardening question, email Larson at firstname.lastname@example.org or call her at 262-857-1945.