Conifer trees across Iowa are showing signs of stress from last winter, including browning or bleaching needles, needle loss and some tree death. This condition is known as winter desiccation, or winter burn.
“This past winter may have been one of the colder winters on record, but we still had several days where the air temperature was above freezing and the soil remained frozen. When this happens, trees use the water reserves in their needles but are unable to absorb new water from the frozen soil,” said Tivon Feeley, forest health program leader with the Iowa Department of Natural Resources. “The tree literally runs out of water.”
The symptoms become more apparent as the days warm and tend to be worse on the windward side of the tree. Reports indicate arborvitae, white pine and white fir have moderate to severe damage from winter burn.
Feeley said if the needles on the tree are dead but buds are alive, new plant foliage will replace foliage lost from winter burn. “However, if both the buds and needles are dead the tree will not recover and will need to be removed,” he said.
There is no way to prevent winter burn. However, tree owners can reduce the risk by properly mulching and watering in the fall prior to the tree going dormant. Watering is especially important in drought years.
For more information contact Tivon Feeley, Forest Health Program Leader, Iowa Department of Natural Resources, 515-281-4915.