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Before winter sets in and the ground freezes, take a look at your trees and shrubs, particularly the younger ones. Evergreens also need some attention prior to freeze up. According to Dennis Adams of the Nebraska State Forest Service, a little preparation yet this fall will go a long ways in keeping them healthy throughout the winter.
Even though deciduous trees do not transpire through their leaves during the winter, they still transpire water to a lesser extent from exposed bark, twigs and buds. Sometimes the loss of moisture exceeds the amount of water the roots can absorb from dry, frozen soil. Desiccation or drying of tissues is the result of the tree being unable to replace water lost through transpiration.
Winter drying injury occurs most frequently during warm dry windy conditions. The sides of the tree facing the prevailing winds is most susceptible to damage. Evergreens, in particular, are prone to winter drying because their needles still transpire during winter. Evergreens are also prone to winterburn which is when temperatures fluctuate between extremes during the day and night resulting in damaged tissue.
Usually large, well established trees can tolerate temporary droughts without injury, but young trees are more susceptible to drought injury. Younger trees do not have the extensive root system to draw moisture from the soil and need supplemental water during dry conditions.
To help prevent winter drying injury, trees should be thoroughly watered in the fall. Fall watering may not be necessary when soil moisture is adequate, but when soil moisture is lacking, fall watering may be critical to help the tree survive the rigors of winter. Relying on the lawn sprinkler is not enough. The soil should be thoroughly soaked to a depth of 2 to 3 feet before the ground freezes. A watering basin , 2 to 3 inches deep and 3 to 4 feet wide, constructed around the base of young trees will hold water until it can percolate into the soil.
Symptoms of winter injury usually do not appear until the following spring or summer. When this occurs it is natural to think the tree suddenly is dying when the damage actually was done several months before. Damaged trees may only exhibit a few dead twigs or entire branches may die, depending on the severity of injury. In severe cases the entire tree may die. Light brown dry appearing needles is typical of winter injury on evergreen trees. Fortunately, this type of injury usually is temporary and most evergreens will recover rapidly as the growing season progresses.
Throw away fallen limbs and if a tree or shrub is very damaged, it should be discarded completely.
Preparation of winter months can be made easier if trees and shrubs are already adapted to their climate. Foresters, nurseries, or Extension Educators are able to help choose appropriate foliage.
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