Lightning strikes carry an immense electrical charge, instantly heating the moisture within a tree’s vascular system. The current transforms water and sap into superheated steam in milliseconds. This sudden, explosive pressure violently tears through the wood structure, causing physical damage. Identifying these signs is important because the tree’s structural integrity may be severely compromised, creating a substantial safety hazard that is not always immediately obvious.
Visual Evidence of a Direct Strike
The most common indicator of a strike is the visible “lightning scar” on the trunk. This damage appears as a deep, vertical groove where the electrical current traveled just beneath the bark. The scar often follows a spiral or helical path down the trunk, sometimes called a candy-cane stripe. The explosive pressure causes the bark to be blown off in strips or patches, which may be found scattered at the base of the tree, exposing the raw wood underneath.
When the strike is severe, the trunk may be visibly split or shattered. This deep splitting occurs when the explosive force penetrates the heartwood, compromising the tree’s main support structure. Wood fragments and large splinters may be scattered nearby. The exposed wood may also show evidence of a “side flash,” where the current jumped from the trunk to a nearby object.
Extensive charring or burn marks are less common than physical splitting and stripping. When scorching occurs, it manifests as blackened or discolored streaks tracing the current’s path. These dark streaks indicate where the high-temperature current momentarily burned the outer layer of wood or sap. These visual clues, particularly the characteristic vertical scar, provide the primary evidence for identifying a direct lightning strike.
Internal and Delayed Damage Manifestations
Lightning damage is not always immediately apparent on the exterior, necessitating a thorough inspection. The electrical current travels through the inner transport tissues (xylem and phloem), creating internal cavities and weakened heartwood unseen from the outside. This hidden damage severely disrupts the tree’s ability to move water and nutrients, initiating a slow decline that may take months to manifest. The strike can also create internal barrier zones that attempt to compartmentalize the damage.
Damage to the tree’s root system is a frequently delayed sign because the current often discharges into the ground. Electricity travels along the root pathways, causing extensive underground injury invisible above the surface. This root injury disrupts the flow of water, leading to signs of stress in the canopy days or weeks later. Sudden wilting or browning of leaves, known as crown dieback, often appears long after the storm has passed.
If a previously healthy tree suddenly exhibits widespread discoloration, needle drop, or a thinning canopy, it indicates a fatal disruption of the vascular system. This delayed decline results from the initial injury preventing proper moisture transport to the crown. Trees that survive the initial event are left highly vulnerable to opportunistic pests and secondary infections targeting the weakened wood and exposed tissue.
Safety Assessment and Next Steps
Once a lightning strike is confirmed or suspected, the immediate priority is a safety assessment of the surrounding area. Check for large, broken branches, sometimes called “widowmakers,” hanging precariously in the upper canopy. A tree with deep cracks or splits in the trunk may have lost structural stability and could fail suddenly during high winds or heavy rain. Instability is heightened if the split extends one-third or more into the trunk’s diameter.
It is important to consider the small risk of a delayed fire, particularly in species with high resin content. Although rare, the strike can superheat the interior wood, causing it to smolder deep inside the trunk before igniting days later. Any signs of smoke, excessive heat radiating from the trunk, or unusual discoloration should be addressed immediately.
The next step involves contacting a certified arborist for a professional evaluation of the tree’s viability. Arborists assess the extent of internal damage and determine if the tree can be saved with pruning and care, or if it poses an unacceptable hazard to nearby structures or people. Removal is often recommended if the strike has damaged more than one-third of the trunk’s circumference or if the tree is located near high-value targets.