Tall trees most vulnerable to lightning storms
by Mall V. Giles
July 11, 2014 01:40 AM | 2295 views | 0 0 comments | 11 11 recommendations | email to a friend | print
Many years ago, one of my very close friends was killed in a lightning storm. Perhaps as a result of this, I am scared of lightning storms to this day. So, here we are again, in the middle of thunderstorm season and in an area of the country where damaging tornados often accompany lightning strikes.

Despite our stately and beautiful, seemingly ever-present trees, we should not take them for granted nor should we ignore some scary facts about lightning strikes and damage. The tallest trees are most vulnerable to lightning strikes. This is mostly true of trees growing alone in open areas such as hills, pastures and those near water. One lightning bolt can equal up to one billion volts. The temperature at the core of a lightning strike can equal up to 50,000 degrees F. A massive amount of heat and electric current are generated. It is important to know that moist tree-tissue inside the tree is a good conductor of electricity. Dry wood is not a good conductor. Lightning can move in a narrow line down the branches and stems all the way to the roots. Or, it can run along a wide pathway and damage entire branches. In this process, tree tissue is destroyed directly by the heat and electrical charges. If stem explosions are visible, it is possible to tell how or where the electrical current moved through the tree. Considerable water loss occurs and pest attack by Southern Pine Beetles can be expected within about 24 hours. The intense heat and explosive shock wave cause much of the tree to be torn apart.

Despite this, most trees struck by lightning are not killed instantly. Slightly more than 20 percent of the trees struck by lightning have no visible symptoms, making it very difficult to predict how seriously the tree has been damaged and if, or when, it should be removed. For example, damage caused to roots is not visible, but can be devastating. The tree declines and may die without any above-ground symptoms. Interestingly, however, the tree may show only leaf wilt and may survive, leafing out again in the following spring.

Visible damage to the tree can appear quite mild, such as: splitting open of the bark, shallow radial cracking of the wood, and leaf wilting from water disruption in the cambium (core of the tree). The most serious and noticeable damage is highly visible and physical: dangling limbs, jagged branches, fires, bark blown off the tree, as well as pieces of wood scattered around the base of the tree. Trees can be blown over as a result of past poor tree maintenance, abuse of the tree and pest and disease damage (such as Fusiform cancers on Pines, root rots on hardwoods).

Storm damage accompanied by lightning can be visible on trees with heavy and lopsided crowns, resulting in stem and branch breakage. A lightning bolt travels down the tree from the top to the roots. Along the way, stems, branches and roots are destroyed. Especially the root damage is not immediately visible. There is considerable water loss and the tree is left stressed and unable to fight serious and rapid pest attack.

Since not every tree struck by lightning is killed instantly (or ever), it may pay off to consider treatment of the tree and the control of damage caused by pest attack. Loss of water during the lightning strike has been significant, so an irrigation routine to reduce tree stress is important. Fertilizing the tree after the storm may increase the health of the tree, helping it to survive the pest attack. As stated earlier, the timing for this treatment is critical, and is best to occur within a very short period of time. Some research has shown that if only one side of the tree has been damaged, the possibility of survival is positive. However, if the lightning strike passes through the entire tree, survival is extremely limited. Interestingly, some trees survive strikes for many years making it very difficult to decide on what to do! Home-owners who have favorite or especially valuable trees, may consider the installation of Lightning Protection Systems.

It may be helpful to contact your local UGA Extension when trying to decide what to do, should you think your “special” tree has been struck by lightning. This is true especially if tree limbs are dangling or have been blown off a tree which then poses structural damage.

Information about Extension Solutions for Homes and Gardens can be found on the UGA Extension website, www.caes.uga.edu/extension/cherokee ; or contact UGA Extension in Cherokee County, 1130 Bluffs Parkway, Suite G49, Canton, GA, 30114, 770-721-7803. The Georgia Master Gardener Extension Volunteer Program is a volunteer training program offered through county offices of the University of Georgia Cooperative Extension. Follow Cherokee County Master Gardeners on Facebook at www.facebook.com/cherokeemastergardeners for gardening tips as well as upcoming seminars.
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