By Beth Berlin
University of Minnesota Extension
Evergreens are a staple and impressive feature in our landscapes. Many evergreen trees and shrubs are showing signs of purple, rust, or browning needles. These symptoms are signs of “winter burn.” Before making the assumption that the tree or shrub is dead and removing it, take a closer look, and give it some time. Unfortunately some evergreens may actually show worsening signs this spring before recovering from winter burn.
Winter burn is desiccation, or drying out, of the needles, and most commonly occurs where evergreens have south or southwest exposure. Often the damage is most severe on the windward side of the plants. Fortunately the deep snow cover added necessary protection, so symptoms might not be evident on lower branching of the trees or shrubs. Unfortunately those with no protection may sustain significant damage and the entire plant may turn brown and may even die.
Some evidence may occur immediately, but often the warm temperatures and winds of the spring actually trigger more dramatic evidence.
First reaction may be to remove the tree or shrub. However, give the plant some time and inspect the plant more closely. If the needles are brown and dead, but the buds and stem near the dead needles are still alive, the plant will regrow new needles to replace the winter burned needles. If damage is more severe and the buds and stems are dead as well, cut back the dead portion to one-quarter inch above the closest live part of the plant. Unfortunately, there may be situations that desiccation was so severe the plant is an entire loss and will need to be removed and replaced if desired.
Winter burn occurs because the plant was not able to store enough moisture in its root system to prevent desiccation of its needles during the harsh winter months. Unlike deciduous plants that drop their leaves in preparation for the winter months, evergreens maintain their leaves and continue to transpire and lose water through their stomata throughout the winter months. As soon as the ground freezes the plant is no longer able to take up moisture through its roots and replace the water lost during transpiration in the winter which results in desiccation.
To assist the evergreens and help prevent winter burn, consistently and thoroughly water the evergreens during the entire growing season right up to the ground freezing in the late fall. Adding three to four inches of organic mulch around the base of the evergreens will help maintain soil moisture. Wrapping evergreens with burlap, a snow fence, or other material before the winter season will help protect the plants from the winter sun and wind. Finally, plan appropriately when planting future evergreens, such as planting them on the east or northeast side of the property where their exposure to the winter sun and wind will not be as extreme.
Winter has definitely taken a toll on our evergreens. However before jumping to a conclusion and removing the plants permanently, inspect them more closely and give them a chance to recover.