Peeling bark is cause for alarm if you don't know what causes it. Bark is like a plant's skin and protects the inside tissue from injury, infection and moisture loss. There are several layers of bark on a rose just as we have several layer of epidermis. The loss of the top layer is not a cause for concern, but if bark peeling goes into the cambium, serious loss of vigour or even death can occur.
There is one variety of rose that is bred to have peeling bark. Lady Banks Rose is a yellow climbing rose that has sloughing bark that adds an ornamental appeal to the plant. The top layer of the bark peels off in long sheets and leaves the trunk with a rustic, interesting appearance that persists in winter long after the flowers and leaves are gone. The older stems have the greatest amount of peeling while the young stems retain the bark until it changes colour.
A fungus called Coniothyrium wernsdorfiae is the source of many bark problems. It attacks the green bark which turns reddish brown and gets purplish black lesions that split and peel the bark. The fungus spreads down the stem and even into the main trunk. Any infected tissue collapses and dies. The infected canes must be removed back to fresh, healthy wood. Use a sanitising spray when making the cuts to prevent spreading the disease. Another fungus called Coniothyrium fuckelii is also responsible for swollen bark that ruptures and peels. It is treated the same way.
Severe sun scald may cause a roses bark to peel. This is more common when another issue such as a pest infestation, has caused the foliage to drop off. The lack of foliage leaves no protection for the plant from the intense sunlight. Cold and freezing temperatures can cause the same problems. If the rose experiences a freeze after it had already released dormancy the water inside the stems will freeze and burst when it thaws. The bark will slough and peel.
Mechanical and Animal
String trimmers are a lazy gardener's best friend but they can cause bark damage on rose bushes. A lawnmower can also make a wound that starts peeling on taller stemmed roses and climbers. Deer have long tongues that can reach around spines and sharp teeth to pull and tear at bark to get at the soft tissue inside. Their feeding activities can leave a rose bush's bark sagging and rolling up. A clue to animal feeding activities will be the presence of identical scrape marks where the teeth drag over the rose tissue.