Winter Protection of Roses

Most roses need some measure of winter protection. The degree of protection your roses need depends on how cold your area gets and on how hardy your roses are. Hardiness is the ability of a plant to maintain dormancy and not die during cold weather. When a plant is dormant, it is in a state of suspended animation, with no growth occurring above or below ground. Tender plants are those that cannot adapt in this way to the cold.

Roses vary widely in their degree of hardiness. Although no one has ever compiled a zone-by-zone hardiness rating for each variety, some generalizations can be made. Typically, old garden roses, miniatures, and shrubs are inclined to be hardy whereas many tea roses, China roses, noisette roses, and modern bush roses are tender.

Natural winter protection

Perhaps the best shelter against winter extremes is the one that nature provides a thick blanket of snow. Snow keeps temperatures beneath it from dipping too far below freezing and from rising so high or so fast that plants are fooled into premature growth. Snow also blocks the wind, which can break branches and rob moisture from the canes and the soil. But snow can also be destructive, its weight breaking or deforming the branches of larger roses. After a snowfall, brush off branches that are sagging. If you live where heavy snowfall is common, you may want to tie large plants together with string to support them against the weight of the snow.

Additional winter protection

In most areas snow is neither deep nor frequent enough to provide constant insulation, so you need to rely on additional means of winter protection. These include covering plants with an insulating material, burying them partially or completely, or, in the case of container-grown roses, moving them indoors before the frost. The time to apply winter protection to outdoor plants is in fall, right after the first normal hard freeze has shocked them into dormancy. Any covering you apply should remain in place until spring and should be removed gradually if possible as warming accelerates to reduce potential losses from an unexpected late freeze. When removing a winter covering, be very careful to not break new canes that may have emerged since you last saw the entire plant.

Mounding soil

The traditional method of protecting roses over the winter is to mound soil over the bases of the canes, to a height of about 12 inches, to protect the frost-vulnerable bud union. It is important that the mounding soil be brought from another area of the garden because removing soil from the immediate vicinity of the plant will expose its feeder roots to the cold air, damaging or killing them.

Winter mulch

Although highly effective, the mounding technique requires a lot of work, as you must move soil into the garden in fall and remove it in spring. A less arduous method if to apply to the same depth a layer of lightweight, nonabsorbent organic material, sometimes called winter mulch. Good materials for winter mulch are shredded oak leaves, straw, or evergreen limbs from unsold or discarded Christmas trees that are available after the holidays. When spring comes you can either remove the mulch or work it into the soil to improve it.

Rose cones

As a winter protection you can also use special caps known as rose cones, which are sold at large garden centers and hardware stores. Made of thick-walled expandable polystyrene, rose cones are usually rounded or multisided containers that taper toward the top and have flanges at the bottom that can be weighted or pinned to the soil. Some have, solid tops; others have covers that can be removed on warm days to keep plants from breaking dormancy too soon. Venting the cones with holes provides additional air circulation that may reduce the growth of molds.

Rose cones come in two sizes: an economical 12-inch height and an 18-inch height for gardeners who don't want to prune their roses excessively to fit underneath. However, even with the taller cones, larger plants need to be cut back somewhat to fit. Tying rose canes together with string before covering them with a cone also helps them fit better. Rose cones can be stacked and stored over the summer and reused from year to year.