You may have noticed that some trees have their lower trunks painted white and wondered why. It isn’t done for appearance but as a protective measure against sunscald, a type of bark damage caused by rapid temperature changes. During winter, cold nights followed by bright, sunny days can cause the bark to expand and contract, leading to cracks that make trees more vulnerable to insects, fungi, and diseases. Young trees with thin bark and orchard trees benefit the most from this treatment until they become stronger.

The white coating reflects sunlight and helps keep the bark at a more stable temperature throughout the day, reducing the risk of damage. Tree markings can also serve other purposes, such as identifying trees that need pruning, removal, or monitoring for disease. In forests and parks, painted markings may indicate trail boundaries, hazardous trees, or protected wildlife habitats. Because paint colors can have different meanings depending on the region, it’s always best to check local guidelines before interpreting them.

If you plan to paint a tree, using the proper material is important. A diluted water-based latex paint is generally recommended because it protects the bark while still allowing it to function normally. Oil-based paints should be avoided, as they can trap moisture and interfere with the bark’s natural processes. While any light-colored paint can reflect sunlight, white is the most common and effective choice.

In most situations, a single coat provides enough protection, although trees in areas with harsh weather may need a fresh application each year. This simple practice is especially valuable for newly planted and young trees, helping them avoid bark damage during their most vulnerable years. Understanding why tree trunks are painted white highlights how a small preventive step can support healthier, stronger growth over time.