When they’re applied in the fall, tree wraps shelter tender young bark from animals and sunscald. Sunscald injures bark when the winter sunshine reflects off of snow, causing a thawing/freezing injury similar to the way skiers can get sunburn from winter snow. Tree wraps shade and protect bark from the winter sun. This is especially important when trees are young, and the bark is smooth and thin.
As trees age, the bark becomes thicker with raised ridges. This makes trees less susceptible to winter bark injury as they get older, and tree wraps are less important then.
Some tree types have thinner bark even as they age. Fruit trees, maples and lindens, with their smooth, thin bark, are best wrapped each fall until trees are older.
Tree wraps are important for protection, but it’s very important to remove them each spring. Tree wraps can damage trees, if left on during spring and summer.
If the wrap is in close contact with the tree, the wrap can exert pressure on the tree trunk, as the tree is trying to grow and expand with spring’s growth. The pressure of contact can cause the tree to be choked and girdled, causing severe damage. There are many trees especially on commercial properties where tree wraps have been left on for too many years, and the constriction is causing tree decline.