We’ve talked about how fall is the best time to plant most trees with a few exceptions (crape myrtles for example). But with colder temperatures now on the horizon, followed by freezing temperatures at some point, let’s talk about how you can give those newly planted trees their best chance at success.

First of all is water. Mother Nature does a pretty good job of providing water for our plants during the winter, but not always. Just know that our trees and shrubs need water in the winter. They are still alive. While the activity above the ground has paused, they are working on expanding their root systems and those roots continue to need moisture.

It takes a little bit of time for a newly planted tree to get properly established in its new home… approximately 1 year for each inch of width of the trunk. For example, if you measure the trunk of the tree about 6 inches above the ground and it’s two inches across. It will take that tree about 2 years to get fully established. So, until then, you are going to need to provide supplemental waterings if nature doesn’t provide.

There are a variety of ways to provide this water, just know that slower applications that allow the water to sink deep into the ground work best. And you will want to water throughout the area within the drip line. The drip line is the outermost part of the tree where water might drip from the leaves.

Evergreen trees are particularly susceptible to a lack of water during the winter because their green needles continue to lose water through during the cold season. So, don’t forget to give them a good drink also.

Next you need to be aware of something called Southwest Tree Injury. Southwest Tree Injury can affect a variety of newly planted, thin-barked trees such as cherry, weeping willow, maples, and a variety of fruit trees. Here’s what happens.

During the height of winter, we oftentimes rise above freezing during the day but then dip down below freezing at night. So, during the day, the sun warms up the bark of the trees. Heat causes the bark to thaw and expand, but then the cold at night causes it to contract. The repetition of this process again and again over the winter can cause the bark to break down. Once this bark is compromised, it never recovers, leaving gaps in the bark of the tree on the southwest side of the tree. It’s the southwest side of the tree because that is where the sun is hitting those trees.

To see an example of this on trees, you can visit most any large, landscaped parking lot. The trees planted there get a double whammy in that they get not only the direct sunlight, but also the light/heat reflected off the parking lot. Next time you find yourself in one of those parking lots, take a look around. If you do, you will likely see a fair amount of Southwest Tree Injury and a variety of trees that have either died or are knocking on deaths door.

These splits in the bark not only inhibit the trees’ ability to uptake water and nutrients but make the tree vulnerable to disease. While properly pruned branches will heal over, the damage from this type of injury rarely does.

Preventing this type of damage on these newly planted trees is pretty easy. You just need to get something call paper tree wrap. All you need to do is loosely wrap the trunk of the tree up to the first branch with this tree wrap and secure it. This will help to minimize the damage caused by the expanding and contracting of the bark during those warm/cold days.

In the spring, remove the tree wrap, then re-install it in the fall. You should repeat this process during the first three years this baby tree is in your landscape. After that, they should have developed to the point where they can take care of themselves.

If you already have trees that have been damaged by Southwest Tree Injury, just know they won’t likely thrive or live as long as their healthy counterparts. Just keep them water and reinforced with 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