Are Sunburst Honey Locust Trees Prone to Sunscald & Cracked Trunks?

Characteristics

• The "Sunburst" honey locust is a deciduous tree that grows in U.S. Department of Agriculture plant hardiness zones 4 through 9. It usually becomes about 40 feet high and wide when mature and has a naturally graceful shape, with slim, arching branches that give the tree a widely spreading, elegant form. Its bark is relatively thin and quite smooth, and its greenish-yellow, inconspicuous flowers attract bees and other insects. In addition to its pleasing shape, the tree's major ornamental value is its leaf color, with compound leaves composed of tiny yellow leaflets that become green in summer and then turn gold-to-bronze in fall.

Winter

• The "Sunburst" locust loses its leaves completely in late fall, exposing the trunk and branches to sun and drying winter wind until the following spring when new growth begins. On sunny winter days, the thin bark on the south and southwest sides of the tree's trunk warms, which can cause cells in the bark to activate as they would in spring. When temperature falls below freezing after sundown, the sudden cold can kill these cells. Significant damage to the tissues under the bark can interrupt water flow from roots to the upper tree in spring, causing some leaves and branches to die. Freezing and thawing of the water layer in the inner bark during winter can also cause the bark to crack or split, with pieces of bark possibly falling from the tree.

Prevention

• Several strategies can help prevent sunscald or bark injury to a "Sunburst" honey locust tree. You could purchase tree wrap made of insulating paper, winding it around the trunk of the tree in late fall. While effective in winter, this wrapping must be removed by early spring, because it can harbor pests during the growing season. Painting a tree's trunk and exposed main branches with white paint also helps reflect sunlight and prevents over-heating of the tree's surface. You could also sink a wooden plank into the ground on the south side of the tree to provide shade. This plank can remain in place year-round, but might look unsightly during spring and summer.

Other Methods

• Preventing stress to a "Sunburst" locust tree while it's growing also helps prevent substantial damage from sun during winter. One of the best ways to accomplish this is to water the tree during any dry spells, aiming for about 1 inch of water weekly. Planting the tree to the north or east of buildings also helps protect it from sunscald, as does planting evergreen shrubs on the south and west sides of the tree, where they'll provide shade in winter. You should also prune large branches gradually, rather than removing many branches at one time, because wounds remaining from branch removal are also susceptible to sunscald during winter.