Friday, August 5, 2011
Lightning Only Strikes a Tree Once?
Any tree can be hit by lightning, but oaks, elm, maple, poplar, ash, spruce, fir, pine and tulip trees are known to be prone to lightning strikes. As they are trees that grow large and tower over the forest canopy damage is not uncommon from the forces of nature. Water and sap in a tree provide a conduit for the lightning as it travels toward the ground. As the lightning travels through the tree, water and sap boil, gases inside the tree expand, and often the wood and bark of the tree can split or commonly explode. When the bark is wet, damage is usually less severe as lightning will travel more along the outside.
Trees struck by lightning can survive many years after a lightning strike, but this is based on the extent of the damage and the treatment of the tree afterward. Most trees that die from lightning strikes years later die as a result of infection or infestation by insects. When pruning can be done to remedy damage, it is suggested. Lightning strikes can be extremely stressful to trees so it is advised that trees be watered in times of drought and fertilized in fall. Do not paint the wound, this can do more damage than good.
To prevent lightning damage a lightning protection system may be installed. Protection systems consist of a series of copper cables attached to the tree’s highest branches and grounded a safe distance from the tree. If lightning strikes the tree, the current flows down the cables to ground. If interested in a lightning protection system, consult with an arborist although the damage may already be done.
During the summer at times of drought leaf abscission may also occur in response to heat stress but we do not suspect that this is the main issue. This issue should also, however, be resolved by watering in times of drought. Fertilize the tree in early fall.
Which trees are less likely to be hit by lightning? -beech, birch, and horsechestnut
For additional information, see http://joa.isa-arbor.com/request.asp?JournalID=1&ArticleID=1862&Type=2