In our area, predominantly Heat Zone 5, almost all roses need some kind of winter protection not only from the cold but also from the whipping winds and wild temperature swings which are the rule here. A heavy blanket of snow may well be the best winter protection since it prevents the soil from getting too cold under it and, at the same time, prevents the warming of the roots which may entice the rose into premature growth.
In recent years, our area has suffered some devastating snowfalls, most of which disappeared in only a few days. To compensate for this, artificial means must be employed to approximate the benefits of long-lasting snow cover. The strategies used range from the simple covering of the base of the rose with an extra 8 to 10-inches of soil or compost to elaborate structures of styrofoam and wood. Bring in extra soil for this since scraping up the soil around the rose bush may endanger the health of its roots.
Housekeeping chores should precede any winterizing programs. If possible, all remaining leaves should be removed from the bushes and all debris should be picked up and disposed of in the trash but not in a compost pile. Many rose diseases can survive the winter only to infect again. The selective pruning should be done and, if the rose is to be housed in a styrofoam cone or structure, the plant should be tied into a bundle short enough to fit the cone.
Bring in extra soil for the rose crown and to surround the base of the cone since scraping up the soil around the cone may allow the roots to be chilled. There are some drawbacks to the cones from small wildlife and fungus diseases. Cones can provide a luxurious winter home for rodents as they dine on rose shoots. When February temperatures soar to 75-degrees and then plunge to 20-degrees the next day, closed structures provide a perfect breeding place for fungus diseases unless their lids are removed only for the duration of a winter heat spell or holes for ventilation are made in the cone itself. On very warm days, apply fungicide into the rose cones.
Modified versions of total coverage include the plastic fences whose walls, composed of water-filled tubes serve as insulation warmed by the sun. Their centers are filled with chopped leaves to protect the rose and its roots. Towers of chicken wire or roofing paper filled with leaves are also successful. The key of all of these open-end approaches is that, in each case, the base of the rose is protected by a mound of soil. A word of warning! There is no effective method for winterizing tree roses outside. They must be taken inside to a cool place such as a basement or garage and watered only occasionally.