Holy electrons, Robin! That’s some extreme lightning damage! This picture was taken on a lakefront home in Kosiusko County. The damage is clearly extensive, and after we evaluated it, there was no choice other than to remove it. The lightning struck at the top (point 1) and exited through the ground near the sidewalk. When the storm potential is great enough between the ground and cloud to create a current, lightning utilizes the tree as a conduit. Since the storm can contain both positively and negatively charged clouds, the direction of the current can differ (although the plasma – the lightning that we see – is always from cloud to ground). Lightning tends to pass through trees because the water in the tree is more conducive to electricity than the air is. The electrical charge instantaneously vaporizes the sap to steam. The extent of the damages on a lightning-struck tree depends on the season, the moisture on the bark of the tree, the moisture inside tree cavities and anomalies within the tree’s structure. It can be pretty significant (see point 2). The best way to protect your trees from lightning is the same way you protect your house: Install a lightning rod system. The metal rod is an even better conductor than the water in the tree, so it guides the charge down into the ground, protecting your tree.
This video does a good job and illustrating how a lightning protection system works to divert the electric charge through your tree.
The charge and the vaporization of moisture within the wood and surrounding soils and concrete created an explosion that shattered the buttress root, produced a hole at the base of the tree (see arrow 3) and destroyed the concrete walkway (see arrow 4). It appears that the grounding of the tree was heightened by the roots contacting the rebar in the concrete.
Jeff Ling is a Registered Consulting Arborist and Co-Founder of TreeMasters, Inc., a full service arbor-care company, located in Fort Wayne, Indiana. It services tree owners with scientific tree management services throughout Indiana, southern Michigan and western Ohio.