A couple of months ago we talked about how fall was the best time to plant most trees and how to plant your trees for best success. If you’ve planted a new tree, Mother Nature has been doing a pretty good job of keeping it watered recently. Just know that they will need about an inch of water each week, so you’ll likely have to provide supplemental waterings during the winter.

Another thing to remember is that if you planted a small, thin-barked tree like a maple, to ensure its success, you’re going to need to do one more thing to prevent something known as Southwest Tree Injury.

When we are in the thick of winter, on most days, we’ll see temperatures above freezing during the day with freezing temperatures overnight. As a result, during the afternoon, the side of the tree facing the southwest gets warmed up by the sun. This warming causes expansion in the cells of the bark. But then in the evening, it gets cold again. The bark contracts with the colder temperatures. This daily expansion and contraction of the tender, thin bark damages the cells in the bark, causing it to crack and split. These young trees never recover from this breakdown of the bark which leaves a gaping void in the bark, resulting in a shorter life span for the tree.

To see an example of this, all you typically need to do is visit a parking lot that has been landscaped with young trees. In these instances, the variances in temperature are more extreme since the asphalt parking lots collect heat and reflect that up onto the trees. So, more heat combined with cold nights. As a result, many of the trees in these parking lots have trunks with split bark and most don’t make it very long.

Trees most susceptible to Southwest Tree Injury are the thin-barked trees like cherry, weeping willow, maples, and a variety of fruit trees. Fortunately, with a little effort, you can prevent this type of damage using paper tree wrap which should be available at your favorite garden center.

Since you likely spent a fair amount of money on your new tree, an investment in paper tree wrap is well worth it. All you need to do is loosely wrap the trunk of the tree up to the first branch. Then in the spring, remove the tree wrap and save it for next winter. You should plan on repeating this process on the thin-barked trees for the first three years they are in your landscape. At that point, they should be developed enough to take care of themselves.

If you have a tree that has already been damaged by Southwest Tree Injury, there isn’t anything you can do to reverse the damage, just keep it healthy as best you can with water and supplemental fertilization. Good luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo:Tom Ingram