Lightning is a tree killer. Typical strikes generate a current between 20,000 and 50,000 amps at 100,000 volts. Many times when lightning strikes a tree it will travel only partially down the trunk and then side-flash to an object that offers less electrical resistance. That object could be another tree, your home, or even you if you were luckless enough to be nearby during a direct strike. Installing a lightning protection system in a valuable tree can reduce the risks related to lightning strikes.
When Lightning Strikes a Tree
Occasionally a lightning strike will annihilate a tree, shredding the bark and shattering the trunk, leaving only a woody carcass and a massive cleanup. But more often, trees will decline and die a slow, lingering death after a lightning strike. Proactive and proper care for trees prior to a strike will give a tree the best chance of surviving damage from lightning. Successful strategies for after-care are limited, but can still be useful in assisting the tree to recover.
The electrical charge needs a path to the ground and will often destroy major roots as it exits the tree and dissipates into the surrounding soil. If some roots are undamaged, supplemental watering can help an injured tree recover.
Properly installed lightning protection for trees will safely conduct the electrical charge to the ground by providing a preferred path for electricity to flow harmlessly away from vital tree tissue.
Installation of Lightning Protection for Trees
Tree lightning protection consists of air terminals, quarter inch copper cable, copper drive fasteners, bonding clamps, grounding rods and/or grounding plates. The copper cable should be installed without any sharp bends and should never turn more than ninety degrees. Drive fasteners should attach the cable to the tree every 3 – 6 feet. Trees with crowns less than 35 feet wide don’t usually need any branch conductors and a single conductor attached to the trunk will suffice. Grounding rods are typically 8 feet long and located at least 10 feet away from the tree trunk. Proper installation will ensure that the ground terminals are further than two feet from any building and preferably further away from any other tree or structure.
A professional installation will include a map containing the direction and distance of the ground terminal(s) from the tree and any other nearby structure. Copies should be retained by both the contractor and tree owner for future reference.
