With winter just around the corner, Oklahomans can expect colder temperatures, dry spells, along with snow and ice. All of these elements can have a negative impact on the trees in the landscape.

 

Although the state hasn’t dealt with prolonged freezing temperatures this year, gardeners still need to be thinking about protecting young, thin-barked trees from southwest injury. This occurs on the south and southwest side of the tree trunk when the exposed bark warms up on sunny days. Without their leafy cover, branches, and more specifically, the trunks of trees are exposed to higher temperatures from direct sunlight. This activates dormant cells, which become active due to the warmth. However, those cells can be damaged when the temperature drops below freezing during the cold nighttime hours. In fact, the temperature differences between the north and south sides of trees can be as much as 70 degrees.

 

Thin-barked trees such as maple, crabapple, birch, redbuds and ash are susceptible to southwest injury, and young trees are especially vulnerable. Damaged bark and cambium dry out, crack and separate from the wood, eventually falling away and exposing dead sapwood.

 

Healthy trees have the best chance of recovering from southwest injury, which also is known as sunscald. Ensuring trees are healthy and fully hydrated before the ground freezes is a good start. What other steps can homeowners take to protect their trees?

• Keep the lower branches on young trees for a few years until they grow thicker bark.
• Find a way to block the trunk from the sun, such as planting it in the shade or covering it with tree wrap.
• Shade it with a light-colored board or fence on the south and west sides of the tree.

Wraps should be applied in late fall but removed in the spring after the last hard frost. This is important because if not removed soon enough, they can attract insects and prevent tree diameter growth. In addition, wraps that are applied too tightly will inhibit growth.

 

Plastic wraps should fit loosely and include holes or slits for good air movement. It’s a good idea to check the wrap periodically through the winter for trunk damage and insects.

 

How do you treat southwest injury? While there isn’t a magic shot that will fix the tree, keeping it as healthy as possible will help it recover. Damaged bark will eventually peel off, which leaves the underlying wood of the tree exposed, which can look like an invitation to pests and diseases. Keep a close watch for any fungi or insect infestations and treat accordingly.