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One million+
That’s the number of trees struck by lightning in the United States each year. While few trees die immediately, strikes often cause serious structural weakness. This weakness increases the risk of falling limbs and predisposes trees to insect and disease infestations. Lightning strikes to trees also pose a risk to adjacent property. Although damage may not always be visible to the untrained eye, trees in this state can die within a few years, and worse, often present a serious safety hazard.

Lightning protection systems are available that can minimize the risk of a potentially devastating lightning strike. These systems use copper conductors connected to a ground rod to reduce tree damage and conduct the electrical charge to the earth where the energy is dispersed. They have an excellent record of protecting trees.

In fact, lightning rarely damages trees installed with a system according to ANSI (American National Standards Institute) A300 Standards, which were adopted by The Tree Care Industry Association in 2002. While lightning strikes are unpredictable and protection cannot be guaranteed, systems are more effective and more affordable under these new standards.

To help grounds maintenance professionals determine if lightning protection is a worthwhile investment for their property, we asked E. Thomas Smiley, Ph.D., an arboricultural researcher at the Bartlett Tree Research Laboratories, a few questions.

Q: Why should lightning protection be installed?
A: Aside from the obvious, that they protect trees from damage and even death, a lightning protection system can also be a safety precaution. Struck trees often incur torn bark, damaged branches, and other structural issues. These issues significantly increase
the risk of falling branches, which can be hazardous, particularly on properties where people walk and congregate.

Q: What trees should be protected?
A: There are three landscape settings where protection is highly recommended. First, tall trees growing close to buildings. These trees may attract lightning which can ‘side flash’ to the building. Second, trees in outdoor recreation areas where people congregate. And
finally, high value and historic trees.

Q: Are different tree species more susceptible to a strike?
A: Yes, susceptibility does vary by species due to their bark and internal electrical resistance characteristics. Tulip poplar and black locust are considered the most susceptible, and therefore are higher priorities for protection. Ash, catalpa, elm, hemlock, maple, oak, pine and spruce are other species that display a susceptibility to strikes.

Q: Will protecting trees close to a building protect the building as well?
A: You cannot count on a tree lightning protection system to protect an adjacent building. If you are concerned about a building, you should look into a having a system installed on that structure.

Q: Will a system increase the chance of a lightning strike?
A: Systems do attract lightning, but in a relatively small area. If a strike is coming down within a 50 to 100 foot radius of a protected tree, it is likely to be diverted to the tree’s system. This is good because the system will help direct the charge into the ground and reduce the potential for damage to the tree.

Q: Do lightning protection systems require maintenance?
A: Yes. Periodic maintenance consists of annual visual inspections from the ground and a closer, in-tree inspection about every five years or whenever the tree is pruned. The main elements of the system that need maintenance are: (1) drive fasteners which can be overgrown by the tree, (2) the air terminal which stays at a fixed height while the tree grows upward and (3) conductors which can deteriorate or be severed. Maintenance is vital to ensuring the system can perform to its full potential.

Q: How can someone know if they need a lightning protection system?
A: A Certified Arborist can conduct a property inspection to help determine the need for lightning protection. A knowledgeable arborist can identify high-risk trees and properly install and maintain a system to help protect your trees and your property.

E. Thomas Smiley has a Ph.D. in Urban Forestry and is a scientist at the Bartlett Tree Research Laboratories, a 350-acre tree and shrub care research facility in Charlotte, N.C. As the research branch of the leading tree care provider, Bartlett Tree Experts, the Laboratories are at the forefront of arboricultural knowledge and are continually developing new methodologies for the benefit of the industry as well as Bartlett’s customers.