The damage caused by rapid temperature changes is known as sunscald. During cold weather, sunlight can heat the bark on the sunny side of a tree, causing the living tissues beneath the surface to become active. When nighttime temperatures fall quickly, those tissues freeze again before they can adjust, often leading to cracks or splits in the bark. These injuries weaken the tree and may allow insects, fungi, or diseases to enter.

To reduce this risk, many farmers, gardeners, and municipalities apply a diluted white latex paint to the lower portion of the trunk. The white surface reflects much of the sunlight instead of absorbing it, keeping the bark at a more consistent temperature throughout the day. By minimizing sudden heating and cooling, the paint greatly lowers the chance of winter bark damage.

Young trees and recently planted trees benefit the most from this protection because their thinner bark is especially vulnerable to temperature fluctuations. Fruit trees, ornamental trees, and newly planted shade trees are commonly treated before winter arrives. In some cases, specially designed tree wraps are also used to provide similar protection without paint.

The practice is inexpensive, easy to apply, and highly effective when done correctly. Rather than serving as decoration, the white coating acts much like sunscreen by shielding the tree from harmful temperature extremes. The next time you notice white-painted trunks along roadsides, in orchards, or in parks, you’ll know they represent a simple act of preventative care. That small layer of paint helps trees survive harsh winters, stay healthier, and continue growing for many years to come.