Many factors determine whether a tree survives a lightning strike

With the recent heavy thunderstorm activity in our area, lightning has struck trees on the property of many local homeowners. Afterward, they are concerned whether or not the trees will survive. The severity of the damage depends on the intensity of the lightning strike, the level of damage it causes and the overall health of the tree.

What happens when lightning strikes a tree? The intense heat of the lightning causes the liquids inside the tree to turn to gas which increases the pressure inside the tree. The end result is the tree being blown apart, stripped of its bark or set on fire.

Sometimes internal damage is not visible on the outside. The electrical current from a strike will often flow underground following the roots outward. It will sometimes visibly cause long gashes on the surrounding ground. Tall trees, especially those growing alone in open spaces or even among other smaller trees, are most likely to be hit.

Lightning not only poses a risk to trees, but it can damage structures as well. Damage occurs when lightning hits the tree and “flashes” or “jumps” to electrical conducting materials such as downspouts and other metal objects on the building. Lightning can set the structure on fire and damage electronic devices inside. Structures within 10 feet of trees that are taller than the roof are at greater risk of damage.

A lightning strike can cause the tree to become severely stressed. Some trees die rather quickly while others may take months or years to die. Others may not perish at all. The species, health and age of the trees will determine whether or not it will survive. The best course of action is to have a certified arborist evaluate the tree and assess the level of damage as to whether or not the tree can be saved.

For recommendations for arborists, go to the Georgia Arborist Association website at www.georgiaarborist.org. Immediate repairs are usually limited to cleaning up debris on the ground, cutting off the damaged bark and removing the branches that pose a danger to people and property.

The tree will require additional amounts of water and fertilizer applied to its root zone to increase its chances of long-term survival. Stimulating root growth will improve the movement of nutrients and water to the upper parts of the tree. Lightning damage increases the likelihood of insects and diseases attacking the tree. However, the exposed bark should never be painted. Doing so may increase the level of damage by providing a favorable environment for these pests. Improving the overall health of the trees is the best way to prevent pest problems.

To reduce the threat of lightning damage to vulnerable trees and your home, a lightning protection system can be installed. Special consideration should be given for historic trees, trees that have a high economic value, and any large one within 10 feet of a building. The system is installed by attaching a series of copper cable from the top of the tree, down through the main branches and then placed out beyond the root zones to be grounded. Due to the hazardous and tedious nature of the work, only licensed and trained professionals should install a lightning protection system on trees. It should be inspected on an annual basis to keep it maintained. If lightning does strike the tree, the current will be conducted down the cable safely to the ground.

Lightning can seriously injure or kill trees. Consultation with professionals is critical in assessing the survivability of the tree and whether or not any actions to improve its chances of surviving are warranted.

Timothy Daly is an Agricultural and Natural Resource Extension Agent with Gwinnett County. He can be contacted at 678-377-4010 or tdaly@uga.edu.