For years, I’d walk past trees with their lower trunks painted white and never give it much thought. Maybe it was decorative. Maybe it was tradition. Maybe landscapers just did it because someone before them always had. I certainly didn’t imagine it served a real purpose. It wasn’t until a conversation with a local tree specialist that I finally learned the truth: that simple white paint can be what stands between a young tree and serious winter damage.
If you’ve ever wondered why people go through the trouble of painting the bottoms of trees, you’re not alone. But there’s a surprisingly practical reason behind it, and once you understand it, the whole thing suddenly makes perfect sense.
Many markings on trees are meant to send messages to people. Orange spray paint usually means a tree is marked for removal. Blue marks often relate to surveys and property lines. Purple is a warning—private land, no trespassing. These markings communicate human intentions.
White paint, though, is different. It isn’t a message for us. It’s protection for the tree.
The issue starts in winter. Most people assume trees struggle simply because of how cold it gets. But the damaging part isn’t the cold itself—it’s the sharp temperature swings. On sunny winter days, the sun warms one side of the trunk, especially the south and southwest sides. The bark absorbs that warmth and expands slightly. Then evening hits, temperatures drop hard and fast, and the bark contracts.
That rapid expansion and contraction—warm to freezing within minutes—can cause the bark to crack in long vertical splits. These injuries are known as “sunscald.” At first they look harmless, but over time those fissures weaken the tree and invite in insects, bacteria, and fungi that can cause lasting harm or even kill young trees entirely.
Sunscald is especially common in young trees with thin bark and fruit trees growing in open spaces with direct sun exposure.
This is where the white paint comes in.
White reflects sunlight. By painting the lower trunk in a light-reflective color, you prevent the bark from overheating on bright winter days. If the bark doesn’t warm too much, it won’t cool too quickly, and the expansion–contraction cycle that causes cracks slows down. Think of it as putting sunscreen on the tree—simple, protective, and surprisingly effective.
People have used this technique for generations. Farmers, orchard owners, and city arborists continue to do it today, especially in places with harsh or unpredictable winters. And it isn’t just a random slap of paint. The coating is applied carefully, usually covering the bottom two to three feet of the trunk—the most vulnerable part exposed to direct sunlight and temperature extremes.
But not just any paint will do. Tree-safe white latex paint, diluted half with water, is the go-to choice. It’s light, breathable, and non-toxic. The dilution keeps it from sealing the bark too tightly, allowing the tree to exchange moisture and oxygen normally. Too thick a coat can suffocate bark or trap pests. Too thin a coat won’t reflect enough sun. Getting it right matters.
Gardeners usually apply it with a wide brush, making smooth strokes around the trunk. In orchards, where there might be hundreds of trees, workers often use sprayers to speed up the process. Once it dries, the paint acts like a shield through the entire winter season. Most trees only need one coat per year, though those in extremely cold climates may require touch-ups.
A lot of people think trees are completely self-reliant. Strong. Untouchable. After all, they withstand windstorms, snow, droughts, and decades of weather without much help. But young trees are far more vulnerable than they look. Their bark is fragile, their root systems are shallow, and they can’t regulate temperature as well as mature trees. A bad winter can stunt a sapling’s growth—or wipe it out completely. A thin layer of white paint can drastically improve its odds.
Even in urban areas, painted trunks offer extra protection. Concrete and asphalt create strange heat patterns, warming up during the day and releasing heat at night, creating unpredictable temperature shifts. Painted tree trunks can help buffer those rapid changes, giving stressed city trees a better chance at survival.
Some people worry that the paint is harmful. Modern tree-safe latex paint isn’t dangerous when prepared correctly. It’s one of the simplest and safest protective measures available. And despite what it looks like, this practice isn’t about aesthetics. Arborists will tell you plainly: it’s practical, not decorative.
The tradition is also widespread globally. In many countries—across parts of Europe, Asia, and Latin America—people have painted trees white for generations. Sometimes it’s for sunscald prevention, sometimes for pest control, sometimes for visibility in low light, and sometimes to deter grazing animals. But the underlying logic is the same: giving the tree an extra layer of help.
After learning all this, I started seeing those white tree trunks differently. What once looked odd or unnecessary suddenly felt thoughtful and intentional. Someone cared enough to protect that tree. Someone took the time to help it survive winter safely.
Nature is resilient, but even the strongest organisms sometimes need help.
So the next time you walk past a tree with a white-painted trunk in winter, you’ll know the story behind it. That simple coat of paint isn’t cosmetic. It’s armor. A quiet, protective gesture against the winter sun and cold that could otherwise damage the tree long before spring arrives.
It’s a small act—yet one that can make the difference between a tree that heals and grows, and one that splits before it has the chance.