After the fluctuating mild temperatures we've experienced recently, I was shocked to see my oak tree covered in ice the other morning.
Icicles hung from the branches, thawing as the sun began to rise. My eyes followed the glistening ice crystals and water droplets down the trunk and into the ground above the roots.
That got me thinking: How do freezing temperatures affect my trees? Of course, water is essential to life, but does this necessarily apply to the winter months as well? Or are trees and other plants just frozen in time and forced to wait for replenishment until spring arrives?
Greg Mazur, The Davey Tree Expert Company's Tech Advisor, says, "You want your trees to be fully hydrated going into winter." However, the unseasonable warm weather most people in the U.S. experienced in December and January may leave you wondering whether it is safe and acceptable to manually water your plants in winter. Mazur has the answer: "As long as the ground does not freeze, you can water," he says.
You can follow these suggestions to keep your trees hydrated during cold spells:
- Soak tree roots in November, before the harsh winter weather arrives.
- If necessary, give your trees a good soaking in early spring, before the buds break.
- Use a sprinkler to soak the roots in winter, as long as the ground is thawed.
- Apply an adequate layer of mulch to insulate the ground above the roots.
- Keep moderate snow piles on your beds, which insulate the ground as well.
- Avoid tossing road salt near or around trees to prevent the soil from drying.
Why you should give tree roots attention before, during and right after winter:
- Cold temperatures limit trees' chances to soak up the water they need to survive.
- Once the ground freezes, trees can no longer extract water into the roots.
- Without a sufficient water supply, trees may suffer from desiccation.
- Desiccation may lead to browned or yellowed foliage, starting at the tip of the leaf or needle and migrating to the entire surface.
- Depending on temperature, wind and other climatic factors, desiccation can lead to death.
Watering frequency depends on your location. According to R.J. Laverne, a board certified master arborist and Davey's manager of education and training, a good soaking is necessary earlier in spring and later in fall as you move farther south.
Winter pests may cause similar results
Not all discoloration and plant damage indicate water depletion. Mazur says some winter insect activity can result in a similar appearance, which causes some confusion as to how to diagnose the problem.
White pines are particularly susceptible to eriophyoid mites, for example, which gather in large numbers on the southwest, or sunny, side of the tree to find warmth and feed. Although they're too small to see with the naked eye, eriophyoid mites can seriously deplete evergreens from another source of hydration: sap.
"Eriophyoid mites resemble little shrimp," Mazur says. "They are not very mobile at all - they might cover a little more than 1 inch of a needle in one lifetime." He says thousands may cover entire needles at once, sucking sap from the tree. During the winter months, you can use horticultural oils to treat this pest problem.
Not sure what's browning your trees? Consult a professional arborist to evaluate the damage on your tree. Perhaps he or she will send a needle sample to a local lab to check for mites.
Whatever problems your trees encounter this season, be sure to keep an eye on them. After all, nothing beats that moment when you awake on that first spring morning to look out your window and see beautiful, healthy trees that made it through winter unscathed.