I always used to wonder why some trees have their trunks painted white.
Every time I passed by these trees, I couldn't help but wonder if it meant something important. Was it a warning? A property marker? Some kind of forestry code?
Recently, I learned that there can be a much simpler—and surprisingly practical—reason.
White paint or whitewash is sometimes applied to tree trunks as a protective treatment, particularly on young or thin-barked trees that may be vulnerable to winter sunscald.
And once you understand what's happening, those strange-looking white trunks suddenly make a lot more sense.
You may also have seen colored dots, lines, or other markings on trees. Those can have very different meanings depending on who made the mark and where the tree is located.
But whitewashing is different.
It can be a way of protecting the tree itself.
So why would someone deliberately paint a tree white?
Let's take a closer look.
What Is Sunscald?
Sunscald is a type of winter injury that can affect the trunks and branches of trees, particularly trees with thin or smooth bark.
It may sound strange because we usually associate winter damage with freezing temperatures.
But sunlight can play an important role too.
On a bright winter day, direct sunlight can warm the south- or southwest-facing side of a tree trunk.
The bark heats up.
Then, when the sun disappears and temperatures drop rapidly, that warmed tissue can cool and freeze.
That repeated heating and cooling can damage the bark and underlying tissues.
And that's where whitewashing comes in.
Why Paint a Tree White?
The basic idea is surprisingly simple:
White surfaces reflect more sunlight than dark surfaces.
When an appropriate white coating is applied to a tree trunk, it can help reflect some of the sunlight striking the bark.
That can reduce extreme temperature fluctuations on the trunk during sunny winter days.
In the right situation, that may help reduce the risk of sunscald and related winter injury.
It's not magic.
It's a little bit of physics being put to work in the garden.
Why Are Young Trees Especially Vulnerable?
Young trees often have relatively thin bark compared with older, mature trees.
That makes their trunks more susceptible to sudden temperature changes.
Fruit trees are particularly common candidates for this type of protection in some orchards and gardens.
Trees with smooth, thin bark can be especially vulnerable when they're suddenly exposed to strong winter sunlight.
That's why you may see the lower trunks of newly planted or young trees looking unusually white.
Someone isn't necessarily trying to make the landscape look decorative.
They may be trying to protect the bark.
Does White Paint Keep Trees Warm?
