Question: What trees and shrubs should I try to protect from winter injury, and how?
Answer: Here's a rundown of potential winter-related problems for trees and shrubs, what is susceptible and how to help.
Sunscald: Dead, sunken, dried or cracked strips of bark, usually on the south or west side of a tree. This occurs when the sun warms the bark enough during the day to trigger cambial activity. When the sun goes down and temperatures plummet, the cambium dies.
What's susceptible: Young, newly planted trees. Thin-barked trees, including mountain ash, maples, crabapples, plums and cherries. Trees that have been recently trimmed resulting in new sections of the trunk being exposed to the sun. Trees that receive much sun during winter days, especially those sited near a paved surface that will reflect additional sun onto them.
Prevention: Wrap the trunk with a tree wrap made of light-colored material. This will reflect the sun and prevent the cambium from warming up. Be sure to remove it in early spring; otherwise fungal and insect problems can occur, in some cases enough to kill the tree.
Winter burn: The drying and browning of evergreen foliage. Winter burn is caused when the plant loses too much water through its foliage, which cannot be replaced via the roots because the soil is frozen.
What's susceptible: All evergreens, but yews,, arborvitae and hemlocks in particular. Evergreens cited on a southern or western exposure, where they get a lot of sun, are also most susceptible, as well as those cited where they are hit by harsh winter winds. Sun and wind dry the foliage.
Prevention: Plant evergreens where they won't be exposed to winter sun and wind. Keep evergreens watered well right up until the ground freezes. Protect existing plantings from sun and wind by wrapping them in burlap or erecting a burlap fence to shield them. Or protect them by planting a windbreak of more rugged trees and shrubs.
Animal damage: Bark and stems chewed by mice and other rodents, rabbits and deer.
Susceptible plants: Deciduous woody plants. Evergreen foliage. Many plants may be labeled as resistant to animal damage, but appetites vary by region and extent of hunger.
Prevention: Surround trees and shrubs with tree guards, tree wrap or hardware cloth to prevent nibbling and damage caused by deer rubbing their antlers on the tree. Secure the wrap several inches below the ground to deter mice. For rabbits, the wrap should reach about two feet above the average snow line. Fencing and repellent sprays can also be effective against chewing animals. If you use a tree wrap, be sure to remove it in early spring.
Snow and ice damage: Branches snapped by the weight of ice or snow.
Susceptible plants: New, young plantings. Trees and shrubs that have not been pruned. Delicate shrubs under the eaves of the house or alongside pathways, driveways and the street.
Prevention: When pruning, remove weak branches, crossing branches and branches that are tightly angled against the trunk or another branch. Avoid planting delicate shrubs under eaves where snow can slide off onto them (or must be raked off), or alongside paths and drives where snow will be shoveled or plowed on top of them. Protect existing plantings by building as A-frame over them for the winter. Avoid dumping snow on shrubs when shoveling.
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