Here we are with the beginning of March. The snow I have on my grounds still covers everything. It has piled between two and four feet everywhere. I saw Earth for the first time last week driving along a freeway. Naturally, Earth appeared only on the North side of the east-west road.
With the exceedingly bright sun reflecting off of everything white, this is the time of the year susceptible evergreens and smooth-barked trees are vulnerable to winter sun-scald.
Do you remember last warm season seeing maple or ash trees with ghastly looking vertical wounds on the south or southwest side of the trunk? It appeared as if the tree had split…..cracked wide open deep into the heart of the tree. That most likely is injury caused by sun scald.
Pyramidal arborvitaes and upright yews planted on the south or southwest side of a building, often brown out where exposed to the winter sun. Techny arborvitaes do not seem to be bothered by sunscald, by the way.
I must have twenty five or thirty global and semi dwarf arborvitaes somewhere or another on my grounds.. They have never been bothered by sunscald, for they are out in the open where there is no entrapment of heat from the sun. This year they are still buried under all the snow.
DeGroot’s arborvitaes are occasionally touchy about sunscald injury during their first winter after planting.
With the lengthening day and increasing intensity of the sun, temperatures by afternoon can be very deceiving. As I write this article, I am already sweating from the East sun coming through my office window at 9:20 AM. By afternoon the sun’s rays reflecting off the snow or off any white building can cause temperatures on the south exposure of bark or evergreen foliage to rise significantly. Plant tissue of susceptible species of this sunny part of the plant is stimulated into activity. When again in shade with evening approaching, below freezing temperature will kill the active cells eventually causing bark to split on certain young deciduous trees, or swaths of browned out dead foliage on some evergreens.
Deciduous trees most susceptible to winter scale are apple, crabapple, ash, mountain ash, maple, and linden. Evergreens often sensitive to winter burn are yew, some arborvitaes, and Alberta spruce. Often, although the plant might
Commercial tree wrap is available to protect deciduous trees. You will want do provide some kind of wrap for the young trees because the injury from sunscald is often severe and disfiguring.
For sensitive evergreens you shouldn’t wrap the entire plant. Just place some object to provide at least some light shade to the south-southeast side of the susceptible shrub or small tree.
As these plants age, they often become less sensitive to this kind of winter injury. I’d recommend that you countinue with your tree wrap protection of deciduous trees until the bark matures enough to show a roughing pattern.