Yes, in climates where rose bushes are exposed to winter’s cold and harsh winds, roses need protection to survive winter. Several elements associated with winter can cause damage to roses, including:
cycles of freezing, thawing and refreezing that heave the ground
sudden, early fall freezes
surprise, late spring freezes
Cold temperatures are mostly a problem if bushes have not entered dormancy before really cold snaps. Once a rose bush goes dormant, it is important to keep them dormant.
Consider the following steps to protect rose bushes, especially if you live where temperatures stay below 20° F for considerable periods, without a predictable blanket of snow to shield them.
Let rose bushes harden off and adapt to the approach of winter naturally. Reduce fall watering, stop applying nitrogen fertilizer and stop deadheading. Clean up fallen leaves meticulously. Then, after most of the leaves fall and frosts arrive, protect the bushes.
Prune: Take out dead and weak shoots and any shoots that show signs of disease. Trim long canes by half and shorter ones by a third. Reduce the overall bulk of each bush, so it can be protected efficiently from battering by wind and ice.
Spray: Apply anti-desiccant shortly after pruning to seal in moisture and help resist damage from winter cycles of freezing, thawing and refreezing.
Cover up: Even frozen, the ground is warmer than icy blasts of wind. Protect the graft union by mounding up a 10" -12" hill of dirt, compost, bark dust or some other light, dry material to insulate from winds and cold. A hill of garden dirt conducts heat up from the ground to the lower parts of the bush, however in spring, removing the dirt is hard work. Another approach is to mound a pile of mulch around the canes to insulate and protect them from wind damage. Secure the mulch with straw, conifer boughs or several layers of folded newspaper, weighted down, tied or enclosed in a rose cone or wire cylinder.
A whole rose bed can be protected by constructing a simple wooden frame and attaching sheets of building styrofoam. If building a rose house, make sure it can withstand the weight of snow and rain as well as strong winds. After the thaw, wait to remove dirt or mulch until the ground has thawed in spring and the possibility of a sudden freeze has passed. Be careful not to damage emerging new growth. Move the dirt or mulch to another site or spread it out around the beds or in the paths.
Yes, even where conditions are less severe, roses benefit from maintenance and winter care.
Prune: Limit pruning, because if winter dieback occurs, canes can be pruned later below the dieback. Really tall canes can be cut back to about 3’ to avoid winter breakage, and long canes can be tied or contained in a plastic rose collar, so winter winds cannot whip them around. Take out dead and weak shoots and any that show signs of disease.
Pruning helps control all common rose diseases, so prune diseased stems, severely if necessary. At winter’s end, wait until danger of frost has passed to prune and shape bushes. As the weather begins to warm up, cut canes down to 6" - 8".
Since pruning stimulates new growth, resist the urge to cut back roses too early in the spring to avoid damage from a surprise frost. Encourage rose bushes to grow in an open shape that allows air movement within the plant.
Winter watering is very important for rose survival in dry areas. Water your roses every 4-6 weeks when there is no snow cover and the ground is not frozen, approximately 2-3 times throughout the entire winter.
Clean up meticulously to discourage black spot and other diseases that thrive in warm, moist places. Rake and discard all fallen leaves, rose hips, dead flowers, and other plant trash. Also, remove not-yet-fallen leaves that are infected with powdery mildew.
Don’t compost diseased material in case your compost pile doesn’t get hot enough to kill the disease-causing fungi; send it to the landfill instead. The fungus that causes blackspot survives winter on living or dead plant tissue, including leaves and stems that have been infected. In winter and spring, the spores are splashed by rain or watering onto new leaves, allowing the disease to spread. Newly emerging leaves are most susceptible to this fungus. If a leaf surface stays wet for 24 hours or longer, spores germinate and grow into the leaf tissue.
Spray: Consult your local garden center for product recommendations and details on spray schedules for your area.