CORVALLIS - Recent cold temperatures have been shocking to some trees and shrubs. The leaves on evergreen leafy species such as rhododendrons and azaleas may droop and curl.
"They aren't sick," said Ross Penhallegon, horticulturist with the Oregon State University Extension Service. "They're just reacting to the cold temperature spells of late fall and early winter. 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.
"Cracking often happens when severe weather comes before the plant has had a chance to go completely dormant," he explained. "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.
"Get rid of the branch stubs that could otherwise be a source of infection and insect problems," he said.