Weather Library > Lightning Strikes to Trees

By DAN ROBINSON
Storm Chaser/Photographer
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Direct Hit
It's a proven fact - standing under a tree is one of the most dangerous places to be in a storm. And for a good reason - trees protrude from the earth's surface, making them frequent victims of direct lightning strikes.

Electricity seeks the path of least resistance, and the moisture (sap and water) inside a tree is a much better conductor than air. The result: a tree provides a preferred path for lightning to reach ground.

Interesting things happen when lightning strikes a tree. Some trees escape completely unharmed by a direct hit, while others sustain moderate to heavy damage. Death of the tree is common in the latter instance.

Generally, lightning will do at least one of the following three things when it decides to victimize a tree:

Scarring, No Damage, and/or Complete Destruction.

How can you prevent lightning from damaging your favorite tree? Read about lightning Protection & Prevention for trees.

SCARRED

In most trees, the area just under the bark layer contains moisture in the form of sap and water. And since water is a better electrical conductor than wood, lightning striking a tree tends to travel just underneath the bark. The explosive expansion of the lightning's return stroke will literally blast off the bark, and sometimes some of the wood, along the length of the lightning channel. The result is a visible scar along the trunk of the tree (watch animation below).

Bark strips
Bark Strips
The image at right shows two strips (front and back views) of bark blown off of a tree by lightning. Click on the image for a larger view.

Lightning Scar Formation

Bark strips
Scarred
Often, the core of the lightning channel will carve a half-inch wide groove in the wood in the middle of the scar. If the lightning flash consisted of more than one return stroke, there may be two or more of these grooves in the scar. The image shown under the menu bar on the top-left side of this page shows a scar with two grooves.

Unfortunately, tree specialists say that there's not much that can be done for a tree that has lost a significant amount of bark. "Your tree may survive for a while," says Helen Southall of West Virginia Tree Expert and Nursery Co. in Ripley. "But eventually nature will take its toll on the tree."

Unlike skin on humans, bark can't be grafted or transplanted to repair the injury. "With a gash of removed bark, a tree won't be able to withstand dry spells or freezing winters," says Southall. "The injury also leaves the tree exposed and defenseless against disease and parasite infestation."

Devastating damageThere is, however, a way to protect your trees before the lightning strikes.

View trees with lightning scars in the Tree Damage Gallery.

COMPLETE DESTRUCTION

In some trees, especially those with dying or rotting areas in the trunk, the predominant moisture may be concentrated deep in the core of the tree. In this case the lightning, seeking the well-conductive moisture path, will travel through the center of the tree with devastating results. The powerful, explosive return stroke(s) will blow the trunk apart like a stick of dynamite- sending large branches flying, splitting the trunk in two, and/or reducing large parts of the tree to splinters.

ESCAPING UNHARMED

If heavy rain has soaked the outside of the tree, a lightning strike may flash over the outside of the bark, leaving little or no damage.

Make your own observations

Take a walk around your neighborhood or a local park or cemetery and see if you can find a tree with lightning damage.

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