A tree struck by lightning is a dramatic event resulting from immense electrical energy. Lightning strikes can carry up to 100 million volts and generate temperatures reaching approximately 50,000 degrees Fahrenheit. Trees, especially those with high internal moisture, are poor electrical conductors. The current primarily travels through the sap and water just beneath the bark, and this resistance to electrical flow causes the spectacular physical signs of a strike. The energy exchange results in damage ranging from immediate, explosive scars to subtle, long-term internal injuries.
The Signature Scar: Trunk and Bark Damage
The most immediate evidence of a lightning strike is the explosive damage to the trunk and bark. When the current travels through the water and sap layers, the intense heat instantly vaporizes this moisture into superheated steam. This rapid expansion acts like an explosion, forcefully blowing the bark away from the wood.
The resulting scar often appears as a long, vertical groove or furrow running down the trunk, sometimes spiraling along the wood grain. Strips of bark can be completely stripped off and scattered several yards away. Exposed wood may show a blackened or charred appearance, indicating where the current traveled. In severe cases, the entire trunk may be split or shattered, compromising its structural integrity.
Delayed and Hidden Damage: Crown, Branches, and Roots
While the trunk scar is obvious, a lightning strike often causes significant damage that is not immediately visible, particularly in the crown, branches, and root system. The explosive force can travel up into the canopy, causing major branches to splinter or shatter, leaving behind jagged edges. This damage can lead to delayed branch failure, posing a risk long after the storm has passed.
Damage to the tree’s vascular system (xylem and phloem tissues) can cause symptoms to appear days or weeks later. Leaves or needles may begin to wilt, turn brown, or become scorched, often on one side of the canopy, signaling disrupted water transport.
Below ground, the electrical current often disperses into the soil, frying the shallow root system. This root damage leads to a slow decline, manifesting as yellowing leaves, thinning foliage, or a gradual loss of vitality over one to three years, even if the trunk appears intact.
Assessing the Aftermath: Structural Integrity and Safety
A tree struck by lightning requires a careful assessment of its safety and structural stability. The internal shock wave can pull wood fibers apart and create deep fissures that weaken the entire stem, even without a visible external crack. Immediate hazards include smoldering wood, which can ignite a fire, and large, broken limbs hanging high in the canopy.
If the trunk is split, or if the bark is stripped from more than one-third of the circumference, the long-term risk of decay and structural failure increases significantly. Trees near structures or in high-traffic areas should be immediately evaluated by a certified arborist to determine the extent of internal damage.