What happens when lightning strikes a tree?

01

Why does the bark blow off?[1]

Because the water under it turns to steam almost instantly. Current follows the moist cambium layer just beneath the bark, heating it to thousands of degrees in microseconds, and the steam pressure blows the bark outward, sometimes throwing pieces tens of meters.

The path follows moisture because wet tissue conducts far better than dry heartwood. That is why the damage is typically a long vertical strip rather than a hole, tracing the route down the trunk that offered the least resistance.

When a trunk is thoroughly wet from rain, current can travel down the outside instead and cause much less damage. The most destructive strikes hit trees whose interior is wetter than their surface.

02

Which trees get struck most?[2]

The tallest and most isolated ones, regardless of species. Height, pointed shape and isolation dominate. Species matters only indirectly, through typical height, root depth and how much moisture the wood holds.

Oaks appear frequently in strike records mostly because they grow tall, live long and often stand alone in fields and parks. Deep-rooted species with high moisture content do offer a slightly better conductive path to ground, which reinforces the pattern.

The practical takeaway for safety is unchanged: a lone tree of any species in open ground is a preferred target, and sheltering under one is the second leading cause of lightning casualties.

03

Will a struck tree survive?[1]

It depends on how much of the cambium ring was destroyed. A single narrow scar down one side often heals over several seasons. Damage that circles the trunk cuts the tree's transport system completely, and it will die.

Give a marginal tree time before deciding. Struck trees often leaf out normally the following spring on stored reserves and then decline in the second or third year, so an early verdict on either side is unreliable.

04

Is a struck tree dangerous afterward?[3]

It can be. Internal splitting weakens the structure without showing much from outside, and struck trees drop limbs or fail entirely in later storms. A damaged tree within falling distance of a house, road or power line needs a professional assessment.

The delayed failure is what catches people out. The tree stands through the storm that hit it and comes down in a routine gale a year later, because the internal damage was never visible from the ground.

Fire is the short-term risk. A strike can leave a tree smouldering internally for hours or days, which is the same holdover mechanism behind lightning-ignited wildfires, and it applies to a garden tree as much as a forest one.