By Paul James

This weekend, I plan on wrapping all the presents I have hidden in my closet, the garage, and under the bed. I just hope I can remember where I stashed everything! And when I’m done, I’ll head outside to do some more wrapping, not of gifts, but of two young pear trees. Why, you ask? To prevent a nasty and potentially destructive condition known as sunscald or southwest injury, that’s why.

So what the heck is sunscald or southwest injury? It’s a physiological disorder that occurs on the trunks of trees when temperatures drop below freezing and the sun strikes the tree, warming the trunk well above freezing and activating dormant cells. When the sun sets, the trunk rapidly refreezes and the cells die. The resulting damage includes discoloration and cracking or splitting of the bark, which creates invasion sites for pests and diseases.

The damage occurs on the lower part of the trunk on the southwest side of trees, hence the name. That’s where the sun’s rays are most intense. Young trees, including oaks, are especially vulnerable because they haven’t yet developed a thick insulating bark. But smooth-barked trees are also at risk, in particular maples, ash, birch, crabapple, honey locust, and fruit trees.

The easiest way to prevent the problem is to wrap the trunk of the tree from the base to the first set of branches with tree wrap, a flexible and expandable paper material that’s available in rolls. It only takes a few minutes to apply, and it’s extremely effective. Some folks swear that the white-colored wrap is the most effective because it reflects the heat of the sun, but it sticks out like a sore thumb. I prefer the more natural-looking, tan-colored wrap. It works great, and from a distance, you can’t even tell it’s there. Just remember to remove the wrap in early spring.

Note: Some tree experts insist that sunscald and southwest injury are actually two distinctly different conditions, with the former occurring in summer and the latter in winter. I use the terms interchangeably.