A lightning strike is one of nature’s most dramatic displays, and a tree often serves as the conduit for this immense energy. A single lightning bolt carries an average of 300 million volts and can reach temperatures of up to 50,000 degrees Fahrenheit, which is five times hotter than the surface of the sun. When this massive electrical discharge connects with a tree, the result is a sudden, violent interaction involving rapid electrical conduction, explosive pressure, and biological damage that determines the tree’s fate.
How Electricity Travels Through the Tree
A living tree is not an efficient conductor, but it offers a path of lower resistance than the surrounding air. The electrical current is drawn to the tree primarily because of its height and the high moisture content of its tissues. Water and sap, which contain dissolved minerals and ions, increase the tree’s conductivity, allowing the current to flow downward toward the ground.
The initial current pathway often develops in the phloem and the cambial xylem-initial cells, tissues rich in moisture just beneath the bark. These layers are the least resistant internal tissues and provide the first channel for the electrical charge. This initial current flow is brief, lasting only microseconds, but it sets the stage for the catastrophic damage that follows.
As the current rapidly builds, the internal pathway cannot sustain the electrical load, leading to “flashover.” The charge jumps from the internal tissues to the surface, traveling down the outside of the trunk, often facilitated by a film of rainwater on the bark. The movement of electricity along this highly resistive path generates extreme heat, which is the source of the mechanical damage.
The Immediate Explosive Damage
The instantaneous, immense heat generated by the current traveling through the tree’s resistive tissues causes the visible damage. This heat immediately boils the water and sap contained within the cells, converting the liquid to superheated steam. The rapid expansion of this steam creates a powerful pressure wave that the rigid wood structure cannot contain.
This sudden internal pressure results in a violent, outward explosion that blasts the bark off the trunk. The characteristic sign of a strike is a long, vertical scar or groove where a strip of bark has been ripped away. This mechanical force can be so intense that it splinters the wood, splits the trunk in half, or causes the entire crown to explode outward.
In cases where the lightning travels just beneath the surface, the blast of steam creates a continuous groove that spirals down the trunk. If the current penetrates deeper into the heartwood, the damage is more systemic, often resulting in deep cracks that compromise the tree’s structural integrity. The event is over in a fraction of a second, leaving behind a physical testament to the explosive force.
Long-Term Survival and Recovery
For a tree that survives the initial strike, the long-term prognosis is determined by the extent of internal damage. The most significant biological consequence is injury to the cambium layer, the thin sheath of actively dividing cells responsible for growth and nutrient transport. If the cambium is killed across a large portion of the trunk’s circumference, the flow of water and nutrients can be fatally interrupted.
A tree may appear relatively unharmed but still decline and die days, weeks, or months later due to this systemic failure. Damage to the root system, caused by the current dissipating into the ground, is difficult to diagnose but can lead to delayed mortality. The tree’s overall pre-strike health, species, and size all influence its ability to compartmentalize the damage and recover.
The exposed wood left by the lightning scar creates a significant wound that invites opportunistic pests and diseases. Borers, fungi, and other pathogens can enter the damaged tissue, leading to decay and structural weakness. To aid recovery, the tree requires attentive care, including consistent watering to support nutrient movement, which is essential for healing.
Trees with smaller scars or those where the damage did not encircle the trunk have a better chance of survival, though they may take several years to recover. Arborists often recommend a “wait-and-see” approach, sometimes for a full growing season, to assess if the tree can successfully wall off the damaged areas. The creation of internal barrier zones is a slow biological response to the instantaneous physical trauma.