Protecting roses through the winter is a process of encouraging dormancy while safeguarding the plant’s most vulnerable parts from environmental damage. The primary goal of this preparation is to prevent the freeze-thaw cycles that can dehydrate canes and damage the plant’s core, along with minimizing windburn and cane breakage. Proper winterization should begin in the late fall, before the first hard freeze, to ensure the rose is fully prepared for its extended dormant period.
Preparing Roses for Dormancy
The first step in preparing roses for winter is to halt practices that stimulate new growth. Gardeners should stop applying high-nitrogen fertilizers approximately six to eight weeks before the expected first frost. Fertilizing too late encourages tender, new shoots that lack the necessary cellular structure to survive freezing temperatures, leaving them highly susceptible to winter dieback.
While growth is slowing, it is still important to maintain proper hydration. Roses should continue to be watered deeply until the ground freezes, as moisture within the plant tissue helps mitigate the damaging effects of cold and desiccation. However, heavy watering should cease to prevent overly saturated soil, which can lead to root rot during the cold months.
Before applying any insulation, all fallen and remaining leaves must be removed from the plant and the surrounding ground. Fungal diseases like black spot and powdery mildew can overwinter in the foliage, ready to reinfect the plant in the spring. A light, preparatory pruning should also be completed to minimize winter damage.
Pre-winter pruning involves cutting back long, whipping canes to about one-third of their height. This prevents wind from rocking the plant and loosening the soil around the crown, limiting mechanical damage. Removing weak, dead, or diseased canes at this time further reduces the chances of pests or disease carrying over into the dormant season.
Insulating the Bud Union and Crown
The most sensitive part of a grafted rose, and the primary target of winter protection, is the bud union—the swollen area where the desired rose variety is joined to the rootstock. If this graft point is killed, the plant will only produce growth from the hardier rootstock below. Protecting the bud union ensures the survival of the desired rose cultivar.
The most effective method of protection is mounding, which involves covering the base of the plant with an insulating material. Gardeners should build a mound approximately 8 to 12 inches high over the crown and bud union. Use fresh topsoil, compost, or shredded bark, rather than scraping soil from the surrounding area, which exposes shallow roots to the cold.
The mounding material acts as a thermal buffer, stabilizing the soil temperature. Mounds created with fresh soil or compost should not contain fertilizer, as this could encourage late-season growth during unseasonably warm spells. Once the mound is established, a rose collar or a cone can be placed over it for added protection.
Rose cones, often made of styrofoam or heavy paper, provide a shell over the mound, shielding the plant from harsh winds and sun scald. Cones should have ventilation holes near the top to allow for air circulation and prevent moisture buildup, which can lead to mold and rot. This layered protection is often sufficient for hardy roses in milder climates.
Protecting Canes and Above-Ground Structure
For less hardy varieties, or in regions with severe winters, the canes that extend above the protective mound also require attention. Tall, exposed canes are susceptible to windburn, where cold, dry air draws moisture out of the stems faster than the roots can replace it.
To mitigate this, the remaining canes on bush roses should be gently gathered and tied together with soft twine. This simple action prevents the canes from whipping violently in the wind and reduces the surface area exposed to drying air currents. The tied bundle of canes is more structurally sound, reducing the risk of breakage from ice or heavy snow loads.
Climbing roses present a greater challenge, as their canes are long and often brittle. In extremely cold areas, the best protection is to detach the canes from their support and gently lay them on the ground, pinning them down, and then burying them with soil or a thick layer of straw. If laying them down is not feasible, the canes must be wrapped.
The vertical canes of climbers or tall shrub roses can be wrapped with burlap, canvas, or a specialized insulating fabric. The material should be porous to allow the canes to breathe, preventing moisture buildup and subsequent fungal issues. This outer layer defends against windburn and sun scald, which can damage bark tissue.
Transitioning Roses Out of Winter Protection
The careful removal of protective materials in the spring must be timed correctly to avoid shocking the plant. Protection should remain in place until the threat of a hard frost has passed, but it must be removed before the rose breaks dormancy and begins to put out new growth. This is typically in mid-to-late March or early April, depending on the climate.
The unwrapping process must be gradual to allow the canes and crown to acclimate to the changing temperatures and light levels. Cane wraps should be removed first on a cloudy day to prevent the sudden exposure of shaded bark to bright sunlight, which could cause sun scald.
The soil or mulch mound around the bud union should also be removed in stages, over a period of several days or a week. Removing the entire mound at once can expose the crown to a sudden late-season freeze or cause the plant to immediately break dormancy in the warmer soil. Once the mound is removed, the remaining healthy canes will be visible.
The final, heavy shaping and cleanup pruning should be performed only after all danger of severe frost has passed. At this time, gardeners should cut back any remaining winter-damaged canes, which will appear brown or shriveled, cutting down to healthy, green tissue. This step encourages robust, new growth for the coming season.