Environmental Injury: Sunscald and Sunburn on Trees

Environmental Injury: Sunscald and Sunburn on Trees

Download PDF
Marianne Ophardt, WSU Extension Area Horticulture Specialist, Rita Hummel, Ph.D., Horticulture, WSU Puyallup Research and Extension Center
Trees can suffer all kinds of injury, including damage caused by the environment. Two types of environmental injury related to temperature are sunscald and sunburn. This publication outlines the symptoms, causes, treatment, and prevention of sunburn and sunscald damage to trees.
Section 3 Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris sit amet pulvinar massa, vel suscipit turpis. Vestibulum sollicitudin felis sit amet mi luctus, sed malesuada nibh ultricies. Nam sit amet accumsan dui, vitae placerat tortor. Vestibulum facilisis fermentum dignissim. Maecenas ultrices cursus diam, eu volutpat urna viverra non.


The symptoms of sunscald and sunburn are similar as both injure the cambium (the living cells in a tree just under the bark that give rise to the annual growth ring). Both are due to damaging temperatures, but sunscald is low-temperature damage and sunburn is high-temperature damage.

Symptoms of Sunscald

Sunscald is characterized by an elongated area of dead bark typically found on the south or southwest side of tree trunks, branches, or both (Figure 1). The area may be sunken with dried, cracked bark that peels off to expose dead wood (Figure 2). Sunscald is also called southwest winter injury because it is commonly found on that side of the tree.

Recently planted trees, young trees, and trees with thin bark are more susceptible to sunscald. Deciduous trees are more prone to sunscald damage than evergreen trees because evergreens usually have lower branches to shade the trunk. Susceptible species include maple, linden, mountain-ash, honeylocust, birch, walnut, crabapple, flowering cherry, fruit trees, aspen, ash, tuliptree, Japanese snow-bell, and willow.

Figure 1. Dead, peeling bark is a symptom of sunscald. (Photo by Steven Katovich, USDA Forest Service, Bugwood.org.)
Figure 2. Symptoms of sunscald also include a sunken area on the trunk with dried, cracked, peeling bark or exposed dead wood. (Photo by Rita Hummel)

Cause of Sunscald

Sunscald happens during cold winter weather and is caused by sudden temperature changes of the bark. On a sunny, cold winter day, cold hardy tissues in the bark on the south to southwest side of the trunk are exposed to direct sunlight and warm up. The warmed bark deacclimates, decreasing its ability to withstand freezing temperatures. When the sun goes down or behind a cloud, the temperature of the bark drops quickly to below freezing and the bark tissues are unable to reacclimate or regain cold hardiness quickly enough to withstand freezing. Living bark tissues are damaged by the freezing temperature, which leads to sunscald injury (Figure 3). For more information on freezing damage, see the WSU Extension Home Garden Series on Cold Temperature Injury of Landscape Woody Ornamentals.

Research has shown significant differences in the temperature of the cambium on the north and south sides of trees. One study of fruit trees in New Hampshire during the winter revealed temperature differences of 50 to 55°F between the north and south side of peach trees and 30 to 35°F between the north and south side of apple trees (Eggert 1944).



Copyright 2016 Washington State University

Published March, 2016

WSU Extension bulletins contain material written and produced for public distribution. Alternate formats of our educational materials are available upon request for persons with disabilities. Please contact Washington State University Extension for more information

Issued by Washington State University Extension and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Extension programs and policies are consistent with federal and state laws and regulations on nondiscrimination regarding race, sex, religion, age, color, creed, and national or ethnic origin; physical, mental, or sensory disability; marital status or sexual orientation; and status as a Vietnam-era or disabled veteran. Evidence of noncompliance may be reported through your local WSU Extension office. Trade names have been used to simplify information; no endorsement is intended.