Winter Burn occurs when an evergreen tree does not have as much water as it needs. The damage usually shows up when spring growth starts. It can range from a few dry needles or brown leaf edges to the entire tree turns reddish brown and dies. Here are some ways to prevent winter burn.
No Dormancy
Evergreens never go totally dormant, even in really cold areas. There are always a few stomates, or pores, open. Water evaporates from these pores. This creates a vacuum that pulls water up from the roots. If the roots can’t draw up enough water to replace the moisture coming out, winter burn occurs.
Root Damage
Trees with root damage are more susceptible to winter burn because there are not as many roots to bring water into the tree. Construction, excessive moisture due to watering the lawn around a tree, and herbicide damage can all damage the roots and cause winter burn. This occurs even if the soil is moist since the problem is with the roots, not drought.
Drought Stress
Drought adds stress to all plants. If there has been a drought during the summer, trees enter the winter with drought stress. This occurs even if the tree now has enough moisture. Drought stress increases the odds of winter burn for that evergreen, like high blood pressure increases the odds of a heart attack in humans.
Frozen Water
When the soil freezes, the water in it freezes, too. That means the roots can’t draw that water up into the plant. Most plants have roots that go below the freeze line. However, there has to be enough water in the soil for it to penetrate below the area where the soil freezes. For the evergreens to stay healthy, it is essential that enough water soaks the soil below the freeze line to get the tree through the period of frozen soil.
Wind and Sun
As wind blows over the open stomates, it sucks water from them. The water has to be replaced by the roots, or the needles or leaves are sucked dry and burn. Winter burn is worse on the side of the tree that faces the wind.
Sunlight causes water loss through evaporation with the same result. Evergreens next to buildings also get reflected sunlight. If the sun is out and the day is warmer, reflected sunlight becomes more of a problem. Not only does the sunlight directly cause water loss through evaporation, but it also warms the tree. If the sunlight raises the temperature of the tree or shrub too much, the stomates will open automatically, increasing water loss. Junipers planted near buildings are frequent victims of reflected sunlight in cold climates.
Prevention Is Key
Prevention is key with winter burn. The damage doesn’t usually show up until the evergreen starts growing in the spring, so you can’t see if a tree is in trouble in the winter. By spring, it is too late to help. By then, the damage is irreversible, and you may lose the tree.
Anti-Dessicant Spray
Wilt-Pruf® is a product that you spray on evergreen trees and shrubs to hold moisture in the tree and prevent winter burn. An ingredient in pine pitch forms a molecular film several molecules deep on the needle. Wind and sunlight remove the layers, one molecule at a time, leaving the moisture in the needle or leaf where it belongs.
Spray Wilt-Pruf® before the first freeze of the year. Be careful to get it on all the parts of the tree, even the inner needles or leaves. Anything you miss may burn. Wilt-Pruf® needs at least three hours of sunlight to cure and start working, so apply it in mid-morning on a sunny day. The temperature has to be warm enough for the spray to set up before it freezes, or it won’t work. You will need to reapply Wilt-Pruf® every three to four months, if your winter lasts that long.
Still Thirsty
Since evergreens are never totally dormant, they need to be watered all winter. Anytime the temperature is above 40 degrees F, check the soil around your tree or shrub. If it is dry, water the tree deeply so the water will go down below the freeze line, where the deep roots can reach it after the soil freezes again.
A good way to water the tree is to set a hose under the dripline and turn the water on until it trickles out. Just a trickle, you don’t want to flood the area, or the water won’t have time to soak in before it runs off. Leave it for an hour to really soak the soil around the tree. Move the hose to another part of the dripline and water another hour. Repeat until all the soil under the dripline is soaked. In the spring, you can revert to your normal watering schedule.
Mulch, Mulch, Mulch
In forests, leaf litter and other debris act as a natural layer of mulch. Pine forests are mulched with pine needles several inches deep. In our managed landscapes, leaves and needles are usually removed soon after they fall. To compensate, we apply mulch around the trees.
Mulching around an evergreen tree or shrub is essential to prevent winter burn. Apply three inches of hardwood mulch in a donut starting from the edge of the dripline and heading to the trunk. Stop mulching three inches before the trunk, leaving a donut shaped layer of mulch around the tree.
Mulch soaks up moisture and releases it gradually so the soil around the tree stays evenly moist longer. Mulch also helps stabilize soil temperature. If you live where there is a big temperature difference between nighttime temperatures and daytime temperatures, mulch will help smooth out the soil temperature swings. By keeping the soil moisture level consistently moist, mulch helps prevent winter heaving, especially in heavy soils.
Need An Evergreen Tree or Shrub?
We have a wide range of evergreen shrubs and trees at TN Nursery. They range from large evergreens like cedar trees to smaller shrubs like green velvet boxwoods. Give us a call at 931.692.7325 and we will help you find the evergreen tree or shrub you need to complete your landscape.
