University of Maryland Extension

Lightning Damage

lightning damage - bark cracked
Tree bark cracked after lightning strike

Trees struck by lightning may exhibit variable symptoms. When lightning hits a tree, water in the cells beneath the bark is heated past the boiling point. The resulting steam causes an explosion that removes a strip of bark. A crack in the bark appears when a continuous groove of bark is stripped along the entire length of the trunk or main branch. A crack that does not run the length of the trunk may indicate a side flash. A side flash occurs when electricity strikes the tree, travels down the trunk, then jumps to an object with less electrical resistance. If lightning strikes a bit deeper, the entire tree may blow apart. The tree may or may not have blackened or charred areas on the trunk. In some cases, the internal wood or root system may be burned without obvious external symptoms. The wide range of damage is related to variability of factors such as intensity of the strike, moisture content on and in the tree, and the type and structure of the tree.

Wait a full growing season to determine the extent of damage caused by a lightning strike. Immediately after the strike prune any damaged branches. If the cambium layer beneath is still moist, loose bark may be tacked in place and temporarily covered with burlap or plastic. Otherwise, remove loose bark, water as needed, and wait to determine that the tree will survive before investing in major repairs or fertilization.

lightning damaged tree trunk

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