In other cases, the charge may move down the trunk and kill the roots before dissipating in the soil, leaving little outward evidence of a strike. Struck trees that are not killed by lightning are weakened and much more susceptible to attack by various insects. Conifers weakened by lightning strikes are often attacked and killed by bark beetles. Historic or other valuable trees growing in locations favorable for strikes can be protected by a lightning protection system. The system does not prevent a tree from being struck, but conducts the electric charge harmlessly to the ground.
Copper cables extend down the branches and trunk from the air terminals.
At that point they are attached to a grounding rod driven into the soil at least 10 feet deep. Installation costs vary according to tree height, diameter, and branch spread. To be effective, lightning systems must meet the standards of the National Arborist Association and must be installed by a qualified arborist. Contact an arborist that has International Society of Arboriculture Certified Arborist or similar qualifications.