Lightning Protection Systems for Trees
August 9, 2013
Photo: Courtesy of UF
Given that Florida has one of the highest rates of lightning strikes in the world, I am surprised at how little people in this state know about how to protect their heritage and specimen trees from loss or damage from a strike. Lightning protection systems for trees have been around for decades and basically consist of three parts: An air terminal in the treetop, a copper cable “down conductor,” and a ground-rod system. The terminal catches the strike and sends it down the cable to the ground rod, which, as its names suggests, dissipates the energy of the strike into the ground.
Lightning will follow the best path to the ground. Since the copper cable is a better conductor of electricity than tree tissue, it draws the lightning and keeps the energy out of the tree, preventing the destruction we normally see when a tree is struck. While the stated purpose of a lightning protection system in a tree is to protect the tree, it might also keep the strike from damaging nearby plants and structures, such as your home, by dumping the strike’s entire electrical charge into the ground. I have often seen unprotected trees receive the strike, only to have it jump off to another tree. In one case, the lightning moved from an unprotected tree into a nearby driveway that had structural metal mesh in it, then moved on to the electric meter of the home next door, taking out the neighbor’s entire electrical system. Since lightning is so unpredictable, no one can guarantee what it will do, even if your tree is protected. The best protection for houses is a properly installed system on the structure. However, having a better path-to-ground than just the tree itself certainly reduces the potential for secondary damage, even though it may not completely eliminate it.
There is another situation when lightning protection becomes very important. When providing structural enhancement, such as cabling or rodding, to trees with weak limbs or other structural defects, I always encourage the addition of a lightning protection system. The metal cabling and structural rod used to reinforce the tree do not increase the chance of a lightning strike; but if it is struck, the metal fittings in the tree’s trunk or limbs could conduct the energy of the strike deeper into the tree, resulting in extreme damage. Such significant damage could require removal of the very tree you’ve invested so much in trying to save. A properly installed lightning protection system grounds all the metal parts, so the energy from the lightning strike can be diverted away from the structural cables, and the tree itself, and into the ground.
Finally, if you do feel the need to protect your trees from lightning strikes, you should hire a company with certified personnel, trained and experienced in the proper installation techniques as outlined in the following industry standard: ANSI-A300, Part 4, “Lightning Protection Systems.” For example, this standard approves the use of copper cable and copper or bronze fittings only in trees, whereas aluminum is an approved material for use on structures.
For additional information, you may wish to visit the website for “The Independent Protection Company” in Goshen, Ind., at www.ipclp.com. This company is one of the few foundries that supply approved lightning protection materials for tree systems. Contact your University of Florida/Leon County Extension Office with questions and concerns about your trees and for information on “How to Hire an Arborist.”
Sam Hand, Jr., is Extension Faculty at Florida A&M University. For more information about gardening in our area, visit the UF/ IFAS Leon County Extension website at http://leon.ifas.ufl.edu. For gardening questions, email us at Ask-A-Mastergardener@leoncountyfl.gov