Winter Damage on Shrubs and Trees
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An increasing number of browning evergreen trees were observed early this spring – likely due to freeze related injury. Some trees and shrubs showed damage to branches, while with others the entire tree may have succumbed. Nebraska Forest Service staff continues to receive calls from landowners about these issues into the summer. Additional damage occurred into May. Several broadleaf trees like elms, ash, honeylocust and others were partially leafed out.
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Most of the damage described above may be from early fall freezes, where temperatures dropped into the single digits quickly and tree tissue had little time to prepare. David Olson, Forest Health Specialist with the Nebraska Forest Service explained, “When this happens, the damage is not usually noticed until the late spring, when outer tips may turn brown or in more severe cases, branches or large parts of the tree will be brown.”
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In other cases Olson said, the damage also may be from prolonged periods of freeze in the late spring. “When freeze occurs in the spring, often the buds that have swelled or are ready to open will be damaged resulting in leaves with holes where the tissue was damaged, or the leaves will be smaller or distorted.” And sometimes the buds may fail to open. The tree will likely produce a new set of leaves, but at a cost to the tree, diverting carbohydrates (energy) from other uses.
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The other damage that can occur from harsh winter conditions is known as winter desiccation. This is when the tree is unable to get enough water and dries out from the harsh seasonal winds. While this can occur due to a root issue, a common cause is simply the tree not getting enough water during the fall. Going into winter, frozen soils also will limit the ability of the roots to pick up moisture, while warm winter winds dry out the top.
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In all cases the best thing to do is to keep the tree as healthy as possible with proper watering and mulching. Although we can’t control the weather, keeping a tree as healthy as possible will significantly improve its chances of tolerating or recovering from extreme weather events.
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Watering a tree on a regular basis is important. Most trees prefer water at different rates and amounts than the lawn. To keep trees healthy, consider watering only once or twice a week. It’s also important to water deeply. Excessive watering can make soil too wet for a tree’s roots. However, not watering deep down through the roots, will result in a lack of any moisture. Be sure to water especially when there hasn’t been any precipitation during that week. A good rule of thumb for trees is 1 inch per week in clay soils and 2 inches per week in sandy soils.
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