URBANA, Ill. – Winter can be a tough time for trees—especially evergreen trees and shrubs, says University of Illinois Extension horticulture educator Candice Hart.
When the ground freezes, evergreens are left to survive on the moisture they have stored up in their leaves, as well as any moisture they are able to take up from the ground when it’s not frozen. Since these leaves are still living and photosynthesizing, they are still using water from the soil in order to survive.
“In many winters, we’re struck with very cold and dry winds that can force more moisture out of leaves while the ground is still frozen,” Hart says. “What results are brown, damaged, and sometimes dead evergreens in the landscape.”
This year take steps to prevent that damage.
The first line of defense is watering. Be sure to thoroughly water any evergreen trees and shrubs in your landscape, well into the winter months. Watch the weather and water evergreens when nature does not supply at least one inch of water per week. As a general rule, provide 10 gallons of water for each diameter inch of the tree. Water only when air and soil temperatures are above 40 degrees Fahrenheit with no snow cover. Newly planted trees under a year old should be watered more than established trees.
Another method of winter-weather protection for evergreen trees and shrubs should be considered at the time of planting. Be aware of the placement of fences and buildings or other structures relative to your tree. Trees receiving reflected heat from buildings, walls, and fences are more susceptible to damage, especially on south or west exposures. Windy sites result in faster drying.
On existing trees or shrubs, use a barrier screen made of burlap or similar material as a wind deterrent. Insert stakes into the ground, stretch the burlap between the stakes and place the screen on the south, southwest, and windward sides of evergreens to create the best protection.
Wrapping evergreens in burlap also offers a great defense from wind. When wrapping, it is essential to leave the top open to allow light in. If you choose this method, it is important to use a material like burlap that breathes, unlike plastic or other solid materials.
“Keep in mind that these evergreens are living, breathing plants and they still need light and air to photosynthesize,” Hart says. “And be aware that wrapping the plant too tightly may result in further injury.”
Antitranspirants—compounds applied to leaves to reduce water loss—will not block the pores of a plant for a long enough time to be effective in preventing desiccation. In essence, you still need to water your plant.
“With proper watering and tree protection techniques, your evergreens can be kept lush and green all year long,” Hart says.