Young trees with trunks smaller than an average human’s arm should be wrapped for the winter to prevent sunscald, also known as southwest injury. This problem occurs in the winter from the dramatic temperature difference between day and night and affects the tree’s trunk on the southwest side where the sun is the hottest. The heat of the sun can rupture cells which causes the damage and damages deep into the trunk, into the heartwood. See picture below.
If sunscald doesn’t kill your tree, it will shorten its life and can reduce fruit production. Since there is no treatment for sunscald, prevention is key. The good news is that, now that you’re in the know, it’s easy to prevent!
A simple tree wrap reflects the intense rays of the sun. They are low cost, easy to get, easy to use, and can be reused for multiple years.
Remove wraps during the growing season. If they are not removed, the darkness provides moist shelter for insects and potential rot which can cause a different set of problems. These wraps also protect against antler damage and are less obtrusive than caging.
Since aspens are native and already have the reflective white bark they do not need wraps to prevent sunscald, but still benefit from the protection from antlers.
Here’s the kind of wrap we recommend and your local nursery should carry them:
For more in depth information, check out this article from CSU Extenstion.
To the glory of the garden! Eva
Eva Montane, certified Landscape Designer & President of Columbine Landscapes Co