Why Is My Cherry Tree Bark Peeling on the Sunny Side?

If the bark on the south or southwest side of your cherry tree's trunk is discoloured, cracked, sunken or peeling while the bark on the shadier side looks normal, the likely cause is sunscald — also called southwest injury in some regions. It is one of the more common bark problems on young cherry trees with relatively thin, smooth bark, and it tends to appear in late winter rather than at the height of summer.

Why sunscald happens in winter, not summer

It seems counterintuitive that sun damage is a winter problem, but the mechanism makes it clear. In summer, the sun is high in the sky, strikes the bark at a steep angle, and the surrounding air temperature is warm — there is no damaging temperature differential. In late winter and early spring, the sun is low in the sky and can strike a tree trunk at a near-direct angle for several hours. The bark surface temperature may rise to 15–20°C or more on a still, sunny winter afternoon, activating the cells beneath. When the sun sets, the temperature drops rapidly toward freezing. The cells that were metabolically active are then frozen, and the tissue dies. This dead area then cracks, dries and peels.

Identifying sunscald versus bacterial canker

Sunscald damage appears on the southwest-facing side of the trunk, typically at knee to shoulder height. The dead bark may be sunken and dry, eventually peeling away. The tissue beneath is brown and dead. Bacterial canker produces similar-looking damage but is accompanied by sticky gum oozing from the affected area, and is not restricted to the sunny side. If there is no gum and the damage is confined to the sun-facing side, sunscald is more likely. Both conditions can be present simultaneously, as the dead zone left by sunscald provides an entry point for canker bacteria.

White trunk paint as protection

Painting the lower trunk and main framework branches with diluted white emulsion paint (not gloss) or proprietary tree paint in late autumn reflects winter sunlight and prevents the temperature swings that cause sunscald. This is standard practice in commercial cherry orchards. Use a diluted interior white latex paint — roughly 50:50 paint to water — applied with a brush to cover the trunk from ground level to the first major branches. Reapply every one to two years. This is particularly important for young trees in their first five years.

Physical trunk guards

White spiral tree guards, cardboard wrapping or hessian tied loosely around the trunk provide similar protection by reflecting sunlight and insulating the bark against rapid temperature changes. Tree guards are removed in late spring and replaced in autumn. They also protect against rabbit and hare damage, making them doubly useful for young trees.