This is a normal reaction to cold weather for many rhododendron varieties. The leaves will return to normal when the weather warms up again, or the plants get used to cold weather. Freezing weather can kill plants and crack the bark and cambium cells around the base of the trunk, according to Penhallegon. Woody plants get caught with too much moisture in their trunks and limbs. Azaleas and the smaller types of rhododendrons are the most common victims.
Damage usually occurs on the south and southwest side of the shrubs.
Protect smaller woody perennials from freezing and cracking by mounding bark dust, wood chips or sawdust around the lower trunk and limbs. Larger bushes and trees can be protected by wrapping the trunks or painting them with white exterior latex paint mixed one part water to one part paint. Or use a good whitewash. Branches may snap off in blustery winter storms. Penhallegon recommends pruning back broken limbs on trees and shrubs.