University of Maryland Extension

Frost Cracks, Sunscald, Growth Cracks - Trees and Shrubs

frost crack

Back to Common Problems - Trees and Shrubs

Even hardy trees may develop sunscald or frost cracks. Tree bark warmed by the sun in winter can reach a temperature as much as 18 degrees warmer than the air temperature. When clouds shade the bark or temperatures drop quickly at nightfall, the bark and cambium layer beneath is damaged. This type of freeze damage is called sunscald.

Frost cracks occur when temperature fluctuations are extreme. Water in the cells of the tree trunk freezes and moves out of the cells, causing the wood to shrink. Tension between the frozen and unfrozen layers of wood is so great that the wood separates, causing a crack. The crack can form suddenly and is often combined with a loud cracking sound. When temperatures warm, the wood absorbs moisture and the crack closes. Frost cracks can reopen and enlarge in subsequent winters and may extend to the center of the tree. Damage to tree trunks in most likely on the south and west sides of the tree where the sun is strongest.

Frost cracks may begin in previously wounded or pruned areas. Proper pruning and avoidance of injury may help to prevent some frost cracks. Tree species prone to frost cracking (those with thin or smooth bark) may benefit from applying white latex paint to the tree trunk. The light color reflects light and helps to reduce temperature fluctuations. The following species are more likely to develop frost cracks: apple, beech, crabapple, elm, goldenrain tree, horse chestnut, linden, London plane, maple, oak, walnut, and willow.


Growth Cracks

Occasionally growth cracks form in the tree trunk as a normal part of trunk development. Growth cracks usually appear when the tree is growing rapidly during periods of abundant rainfall. The bark splits longitudinally when cells in the cambium layer (the conducting tissue just under the bark of the tree) expand more rapidly than the bark can expand. The tissue inside the crack looks like developing bark (smoother and lighter in color). As growth continues, bark covers the crack and no permanent damage occurs. Growth cracks can be differentiated from frost cracks or cankers because there is no heartwood visible, and no decay or oozing from the crack.

crack on tree trunk

normal cracks in trunk

Occasionally growth cracks form
in tree trunks as a normal part of
trunk development

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