Did your tree get struck by lightning? With care, you could save them

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Some early spring storm systems around the U.S. have brought weather typically reserved for summer, particularly when it comes to lightning strikes. Volunteers in Florida, a state that typically receives 33 lightning strikes per square mile each year, have received dozens of calls and emails about lightning in the Jacksonville area, near the northeast coast of Florida.

Wherever you live, trees bear a lot of the damage from lightning strikes but just because your tree is struck does not mean it needs to be removed. To determine the extent of damage to a tree from a lightning strike will require some patience.

Here are some things to keep in mind when your tree is struck by lightning

What causes lightning?

Lightning is formed when negative charged ions collect in a cloud. At the same time, positive charged ions are forming on the ground under the cloud and following it. As the positive charges build under the cloud, they follow the contour of the ground. If they travel up a tree, or another tall object, it may put them close enough for the positive and negative electric charges to make contact. When that occurs, lightning is formed.

Lightning can injure a tree in many ways. Most of the time, the damage is obvious. The heat from the lightning vaporizes the water in the tree turning it into steam instantaneously. The resulting pressure from the rapidly expanding hot steam blows the wood of the tree apart. Typically, this happens toward the outside of the tree, and we see it as a streak down the bark.

Sometimes the evidence of a lightning strike is not so obvious. We may not see the damage because it has reached all the way down to the root system or the interior of the tree. The other thing to think about is that just because there is a streak going down the tree, it does not mean that the tree is going to die. The heat and voltage of a lightning strike are never the same. A tree can receive a minor strike, a major one, or hundreds of variations in between.

What to do when your tree is struck by lightning

Lightning strike treatment in trees comes in two phases. First, take care of any hazardous situations such as broken or hanging branches. Then comes the hard part. The true extent of damage to the tree is not immediately evident right after the strike because lightning comes in an infinite range of voltages and temperatures. The sign of injury that can show up after the lightning strike is typically browning foliage that hangs on the tree. The damage may show up as a single branch browning, or major portions of the tree. The browning foliage indicates the parts of the tree that were damaged by lightning. Since this damage may not be readily visible right after the lightning strike, you should wait a few weeks to months to do any major corrective work. By that time, most of the serious damage will be apparent and a decision can be made as to whether the tree can/should be salvaged. In the meantime, timely irrigation (not fertilization) is helpful in helping the tree compartmentalize the damage. Consult with an ISA Certified Arborist at https://www.treesaregood.org/findanarborist/arboristsearch to determine the next steps.

Can lightning damage be prevented?

It may be advisable to install lightning protection in a tree in certain situations such as when a tree is a historic landmark, a specimen, or other places where people congregate such as a golf course. Lightning protection systems use large copper cables that are installed high in the tree, down the trunk and into a trench in the ground that leads away from the tree where the cable is connected to a ground rod. This protects the tree and the people around it by giving the electrical charge a better conduit to the ground than through the tree. Lightning protection systems can be installed by ISA Certified Arborists and must meet the standards of the Lightning Protection and Grounding Institute or the National Fire Protection Association.

What to do if you are caught in a lightning storm

According to the National Weather Service, there have been 14 deaths by lightning in Florida this year. Nationally 70% of lightning deaths occur in June, July and August, with most of them also occurring during the weekend. We often hear that golfers are struck the most when actually four times as many individuals were struck while fishing than while golfing. Several of the lightning fatalities were on their way to safety when they were struck. To avoid this, it is recommended to move toward a safe place well before the lighting becomes a significant threat. Many parks and golf courses have alarms that go off when lightning is near. If you hear the alarm start, move to shelter immediately.

Finally, if you are caught in a lightning storm and cannot get to a building for shelter, follow the following safety rules recommended by the National Weather Service:

• Avoid open areas. Don’t be the tallest object in the area. If no shelter is available, don’t lie flat, instead crouch low, with as little of your body touching the ground as possible. Lightning causes electric currents along the top of the ground that can be deadly over 100 feet away.
• Stay away from isolated tall trees, towers or utility poles. Lightning tends to strike the taller objects in an area.
• Stay away from metal conductors such as wires or fences. Metal does not attract lightning, but lightning can travel long distances through it.
• If you are with a group of people, spread out. While this increases the chance that someone might get struck, it prevents multiple casualties and increases the chances that someone could help if a person is struck.

As mentioned earlier, lightning does not always mean the demise of your tree is imminent. Our trees provide many ecosystem services, not to mention tree removal can be expensive. Take care of the immediate hazard. Then water your tree, contact a qualified arborist, wait for the damage to become apparent, and then decide what to do. By that time, the tree (and your arborist) will make your decision a lot easier. For a very detailed look at how trees are affected by lightning go to the Tree Lightning Manual by renowned UGA researcher Dr. Kim Coder.

Larry Figart is an urban forestry extension agent with the University of Florida/IFAS.