Preparing a rosebush for winter helps keep the temperature around the plant constant. According to the Nashville Rose Society, "Because moisture in the canes expands as it freezes, quick freezing breaks cell walls inside the canes and destroys plant tissue; repeated bouts of freezing, thawing and refreezing can ruin exposed canes." Winterize a rosebush after there have been several days of hard freezes, to put the plant into dormancy.
Fertilize the rosebush for the last time about 2 months before the first typical freeze date. Do not hard prune or cut any more blossoms after this time, to prevent stimulating new growth.
Remove all leaves from the rosebush, but leave the rose hips. Trim the canes to 30 to 36 inches long. Throw all rose debris away; do not compost.
Spray the rosebush with fungicide or lime sulfur spray; cover all the canes and the base of the bush. Tie the tips of the canes together with twine to protect them from strong winds.
Mound up mulch, straw or leaves around the rosebush to a height of 12 inches. Some gardeners create a cage of wire mesh and plastic zip ties and place it around the rosebush, then add mulch, straw or leaves to keep the materials in place.