On a stormy afternoon in June 1752, one of America's most famous historical figures launched a kite into a thunderstorm. While most people in Philadelphia were taking shelter, Benjamin Franklin, assisted by his son William, flew a silk kite fitted with a metal wire attached to a hemp cord. The experiment demonstrated the connection between lightning and electricity and helped lay the foundation for our understanding of electrical phenomena.
We've all watched lightning flash across the sky as thunderstorms roll through South Louisiana. Louisiana averages 50 to 70 thunderstorm days each year, with most occurring during the summer months. Scientists believe lightning forms when tiny ice particles collide within storm clouds, creating electrical charges. When negatively charged regions in a cloud connect with positively charged areas near the ground, a powerful electrical discharge occurs, producing the light and heat we know as lightning.
Because lightning is an electrical discharge, it seeks the path of least resistance between cloud and ground. As a result, the tallest objects in a landscape are often struck. Although wood itself is a poor conductor of electricity, living trees contain large amounts of water and dissolved minerals that readily conduct electrical current. When a tree is the tallest object in an area, it can become an attractive target for lightning.
According to the Arbor Day Foundation, experts estimate that more than one million trees are struck by lightning in the United States each year. The trees in our landscapes represent substantial investments of time and resources, and many hold sentimental or historical value. Hearing the explosive crack of a lightning strike in a cherished oak tree that generations of family members have enjoyed can be unsettling for any homeowner.
Each year I receive calls from homeowners dealing with trees that have been struck by lightning. Almost everyone asks the same question: Will the tree die? The answer depends on the extent of the damage.
Lightning can carry hundreds of millions of volts of electricity and generate temperatures approaching 50,000 degrees Fahrenheit for a fraction of a second. When lightning strikes a tree, the intense heat can instantly convert water and sap into steam. The rapid expansion of that steam may cause bark to separate from the trunk or wood fibers to split apart. In some cases, long strips of bark are blown from the trunk. Severe strikes may leave deep cracks in the wood, completely strip bark from portions of the tree, or even cause the tree to explode.
A tree's chances of survival depend on several factors, including its health prior to the strike, the severity of the lightning damage, and the care it receives afterward. Trees already under stress from drought, root damage, disease, or other factors are less likely to recover. Likewise, trees suffering extensive bark loss or major structural damage are at greater risk of decline or failure.
The immediate effect of a lightning strike is the death of plant tissue. Once tissue is killed, it can no longer transport water and nutrients or serve as a protective barrier against insects and diseases. Deep trunk splits, major structural cracks, and the loss of more than one-third of the bark around the tree's circumference are generally indicators of a poor prognosis. Trees with less extensive bark damage often have a better chance of survival. However, tree death is not always immediate, and some lightning-struck trees may decline slowly over months or even years.
Secondary damage often occurs when insects and diseases take advantage of weakened trees. The loss of bark exposes inner tissues, making them vulnerable to insect attack. In pines, bark beetles may invade damaged trees and introduce fungi that block water movement within the tree. Ambrosia beetles are also commonly attracted to stressed hardwoods. While preventive insecticide treatments may sometimes be beneficial, they are not always practical or economically justified for homeowners.
So, what should homeowners do after a lightning strike? The first step is to assess the damage as soon as conditions are safe. A licensed and insured arborist can evaluate the extent of injury, identify structural hazards, and recommend appropriate actions. If the tree poses an immediate threat to people or property, removal may be necessary. In less severe cases, a wait-and-see approach is often warranted. Supplemental irrigation during dry periods, proper pruning, and maintaining overall tree health can improve the odds of recovery.
Trees struck by lightning are not always destined for the woodpile. With time and proper care, many survive and continue providing shade, beauty, and memories for years to come.
