This year along the Front Range, we had one of the most beautiful displays of fall leaf color in long time. The right combination of moisture when trees were leafing out in the spring along with mild temperatures into the late part of the growing season allowed our deciduous trees to really shine. Often by now, the temps have plummeted and stopped every growing thing in its tracks, but not so this year. While it looks like the mild temperatures are here to stay, at least for a little while, we still need to take some care in preparing our landscapes for the colder weather that is surely on its way. There are some simple things you can do now to winterize your trees. One such task is tree wrapping.
Trees with thin bark like linden, honey locust, fruit trees, maples and redbuds, along with young trees that were recently planted, benefit from extra protection during the winter months. Protection from what? Sun scald and frost cracks. These are temperature related injuries that can do serious harm to trees, even causing death. Over time the bark of most trees will harden and furrow, at which point wrapping is no longer necessary.
Sun scald and frost cracks occur on winter days when the angle of the sun is low in the sky and temperatures warm up causing the tree’s cells to wake up. Water and nutrients begin flowing in the cambium layer of the trunk. When the sun goes down and the temperature drops below freezing, those active cells freeze and burst, resulting in bark splitting. Eventually the bark sloughs off exposing dead tissue. If you’ve ever noticed a tree with what looks like a scar or obvious damage on the south or southwest side of the trunk, there’s a good chance you were looking at sun scald or frost crack injury.
You can wrap trees yourself or hire a pro to help you out. Tree wrap is available in large rolls at many garden centers and nurseries. It is a thick crepe paper type material that insulates the trunk from temperature fluctuations. It is important to start at the bottom and make your way up to the first (lowest) branch. Allow the paper to overlap approximately 1/3 the width of the roll. By starting at the bottom, it creates a pattern that allows moisture from rain or snow to be shed away from the trunk. If you start at the top and move down, water can get trapped under the paper which can cause other issues. Secure the wrap at the bottom and top with something like duct tape or twine. If you use tape, be sure to keep the tape off the trunk itself and only apply to the paper. The rule of thumb for timing is to wrap around Thanksgiving and remove it around Tax Day. Don’t leave the paper on the trunk throughout the growing season because it can become a hiding place for insects and can hold extra moisture on the trunk which isn’t good for the tree.
While you’re getting your trees ready for winter, it’s also a good idea to add a 2-4” layer of mulch near the base of your trees, but not touching the trunk. Mulch helps with reducing evaporation and insulates the roots against temperature fluctuations. By now you’ve probably winterized your irrigation system, but during warm dry spells like we’ve had this fall, trees (particularly young trees and evergreens) need supplemental water to reduce stress and increase overall vigor. Apply approximately 10 gallons per inch of tree diameter. Giving your trees a little extra TLC over the winter is an investment in their health and longevity.
By Deryn Davidson. Deryn is an Extension Agent – Horticulture at Colorado State University Extension Boulder County. For more information contact CSU Extension at the Boulder County Fairgrounds, 9595 Nelson Road, Box B, Longmont, 303.678.6386, e-mail [email protected] or visit boulder.extension.colostate.edu.