Why Are Some Trees Painted White At The Bottom?

When on a stroll or a drive, you may have wondered why some trees are painted with strange markings, and some are painted white at the bottom. These are painted for different reasons, with the markings largely for loggers, and the white paint for the protection of the trees themselves.

What do the markings you sometimes see on trees mean?

Markings can be anything from orange lines on top of each other to ominous red crosses and enigmatic Roman numerals. These aren't the work of woodland creatures, but are used for a number of reasons in forestry management, as well as logging. So what do they mean?

While there is no standardized meaning for the symbols used across the world, different organizations of course use and understand them when they do so. In the USA, the most common markings you'll see are orange stripes. These marks are placed on trees that are due to be harvested, and have been marked for use in timber, while blue markings indicate the edge of a boundary. As well as a visual aid for loggers and tree surgeons to identify trees to be used for timber, they help forest managers keep an eye on logging activity.

"Stump paint is used to help foresters confirm that trees were properly harvested. Stumps without paint raise a red flag, especially if there are too many," Michigan State University Extension Forestry explains. "Sometimes, an adjacent unmarked tree needs to be cut in order to get at a marked tree. Foresters take this into account when marking a stand, but sometimes leave access a bit tough for a logger."

Alternatively, when a large area of forest is to be cut down, trees that are to be left alone may be marked, sometimes in a blue-green color, or a boundary may be marked in yellow.

Roman numerals are used in the UK on trees that have been measured for their height.

"These are called volume sample trees," Forestry England explains. "These trees are important for estimating the total volume, and are marked using Roman numerals to identify them."

Other trees may be marked with letters like "PL" to indicate that they are near a power line, which will need to be shut off before the tree is felled, while red crosses are another way of indicating that a tree is to be cut down. Trees that are not for timber but are diseased may be marked in the same way.

Why some trees are painted white at the bottom

When trees are painted white at the bottom, this is not a sign for loggers, but to prevent damage to the tree during variable winter temperatures .

"Sunscald is a winter occurrence, more common on young fruit trees such as apple, pear, cherryplum, cherry, apricot and plum," the University of Saskatchewan explains in a post. "The south sides of the tree are usually affected, because of sun reflected by the snow, which warms the frozen bark and cause it to thaw too quickly. This will cause the bark to crack which, in severe cases, can lead to structural damage to the tree."

As the trees mature, they become more resistant to sunscald, the result of thickening bark. But in the interim, people protect trees by painting them white at the base. This reflects away more light, preventing the tree from overheating.