November is winterizing time for our rose gardens here in Michigan, and in most of the northern states. Those who leave early for the south may need to get it done a bit earlier. Today we are seeing more winter hardy large roses in our landscapes, including Kock Out and Home Run, as well as hardy shrub roses. These may get along without winter protection, but most of our hybrid teas, grandifloras, and floribundas need winter protection if they are to avoid significant winter damage.
The main reason roses suffer winter damage is not the lowness of the winter temperature, but the low moisture content of the winter winds. When the rose canes are frozen, the upward flow of water in the canes is impeded, while the low moisture winds dry out the frozen buds and bark. The result is desiccation (drying), causing death in bark and buds. Applying winter protection does not especially improve the temperature conditions, but they serve as windbreaks to reduce the flow of the drying winds over the rose canes, and reduce excessive drying.
The Bloks, the Wiers, and the Schumakers are local rosarians who use numerous rose cones in their rose winterizing. When you use rose cones, you need to cut back the canes to fit under the 12 to 14 inch high cones. Tying canes with twine is often necessary, unless you cut the canes very low. Cones do not keep the roses warm, in fact it is important to ventilate the cones with 2 to 4 holes (1-inch) near the top of the cones (not in the top surface). Ventilation reduces excess moisture under the cone, and reduces mold damage to the rose canes. When you use rose cones, it is important to have a good supply of bricks or rocks to stabilize the cones (keep them in place). Some use 2 bricks per cone, I usually use one brick on top, and a “name stake” driven through the “ear” of the cone to keep them from blowing away.
Most rosarians who don’t use cones, or don’t have enough, use soil mounds, or wood mulch mounds to cover the base of the plant. I generally use a mulch-soil mix to mound the roses that are too large for cones, or when more cones are not available.
Most of our established miniatures receive no winter protection, but some known tender varieties such as Olympic Gold, and Tiffany Lynn get small cones. Newly started miniatures and miniature cuttings may be protected by milk jug covers and a ring of soil. We usually shelter a few of our newer cuttings in our covered window wells, with varying degrees of success.
Outside potted roses need to be buried in garden soil to a couple of inches above the rim of the pot, or sheltered in a cold outbuilding or garage. Tree roses need to be buried completely in a soil trench, or sheltered in a largely freeze protected building or garage.
We have protected climbing roses with combinations of soil mound and burlap wrap, but this year we plan to cut back the canes to within 2 feet of the ground and apply a soil mound. Most of our climbing roses bloom on 1st year wood, and probably bloom better on new canes than on partially damaged old cane growth..