If you garden in a colder zone, you need to offer your roses at least some degree of protection in the winter. Most winter damage to roses is caused by frost heave (damage to the roots) or is the result of sun scald and drying winter winds (damage to the canes). Because even the hardiest of roses can succumb to unpredictable winter weather, it's best to choose a good method of protection before the cold weather arrives.
Give Them a Healthy Send-Off
Healthy roses have a better chance of surviving winter than roses weakened by disease, drought, or nutritional deficiencies. To prepare your roses for the onset of cooler temperatures, stop fertilizing and deadheading them starting in the late summer or early fall. As temperatures drop, start to cut back on watering, but make sure to never let them dry out completely. Before covering plants, rake away any nearby debris to remove any plant material that could potentially harbor pests or diseases over winter. Prune the canes back to a size that accommodates your chosen method of protection, while leaving as many of the remaining flowers intact as possible. The flowers will form rose hips - signaling the plant that it's time to go dormant.
Wait for the Big Freeze
One of the trickiest parts of putting your roses to bed for winter is knowing when to do it. Covering plants too early can be as damaging as not covering them at all. As a general rule, it's safest to wait until you have a week of consistently freezing temperatures and a hard frost has caused most of the leaves to fall.
Protection By Rose Type
These are general guidelines. Exactly how much winter protection your roses will need depends on the severity of your climate, the specific type of roses that you are growing, and how healthy the plants are going into winter.
Climbing or Rambling Roses: Cover the base of the plants with a mound of soil. To leave the stems on their existing supports, wrap them in burlap packed with straw and secure them with twine. In severe winter zones, remove the stems from their supports, carefully bend them over and stake them to the ground, and cover them with at 6 inches of mulch.
Container Roses: When temperatures drop below freezing, move container roses into an unheated garage or outbuilding until the weather warms up again in the spring. Check them occasionally throughout the winter to make sure the soil in the container doesn't completely dry out, but don't give them any fertilizer. Another method is to sink the plant, container and all, into the ground outdoors. Surround the exposed part of the plant with a collar or cage and fill it with straw or leaves.
Hybrid Teas and Floribundas: Apply a final dust or dormant spray before covering plants. Cover the crown of the plant with at least 6 inches of soil, then cover the entire plant and soil mound with an additional 6-12 inches of hay or straw. In harsh climates these rose types may need to be buried.
Shrubs and Old Fashioned Garden Roses: In all but the coldest zones, most shrub roses and old fashioned garden roses require little or no winter protection. In colder zones, mound the plants with straw or hay as you would with more tender roses.
Tree Roses: In all but the mildest climates, remove the support stake and lay the trunk flat on the ground. If the trunk cannot be bent without causing damage, use The Minnesota Tip method (below) to lift one side of the root ball out of the ground so the trunk can lay flat. Cover the entire plant with soil (top, trunk, and exposed roots) and mulch with an additional several inches of straw. Tree roses growing in containers can be moved into an unheated garage or outbuilding until spring.
Mulching Heavy (minimal protection)
In moderate climates, frost heave is seldom a problem and minimal protection may be all that is necessary. Mulch heavily, 3-4 inches deep, around the base of the bush. Pile on leaves or evergreen boughs to protect canes from drying winter winds and sun damage.
Rose Cones (minimal to moderate protection)
Another method of winter protection for roses is the use of polystyrene rose cones. This method is not nearly as popular as it used to be, partly due to the fact that the cones are not well suited for use on large rose bushes, and if you don't use them correctly, you can run into all kinds of problems. If you use this method, make sure you don't cover your plants until they go dormant. Also, to prevent the inside of the cone from heating up on warm winter days (and causing the roses to break dormancy), cut four to five 1-inch ventilation holes around the outside. These holes will help keep air inside the cone moving and prevent it from overheating. Mound soil around the base and use rocks or landscape staples to keep the cones from blowing away.
Hill, Cage, and Cover (moderate to maximum protection)
Mound up soil around the canes to a depth of 6-10 inches (deeper = greater protection). Create a container around your bush using fencing or chicken wire and fill it up with leaves, wood chips, or straw to protect the canes from sun and wind damage. Commercially-made "rose collars" are also available at nurseries, garden centers, and online. It's best to purchase them ahead of time, as they can be difficult to find once freezing weather rolls around.
The Minnesota Tip (maximum protection)
Tie the canes together. Dig a trench out starting at the base of the bush (it should be as long as the plant is tall). Carefully pull the soil away from just below the bud union (graft) and using a spading fork, gently loosen the soil around the roots. When the roots are loose, tip the bush over into the trench and cover it with 2 to 3 inches of soil (you may need to bring in additional soil from outside of your garden to accomplish this. After the ground has frozen, cover the tipped bush with an additional 12 - 24 inches of leaves or straw. Watering the leaves/straw will help form an insulating capsule of ice to help keep the bush dormant. Use chicken wire or fencing to keep the leaves/straw from blowing away.