Tree Struck by Lightning: Will It Survive?

A lightning strike on a mature tree is dramatic and the aftermath is usually ambiguous. Sometimes the tree is clearly finished - split open, bark blown off in sheets, limbs on the lawn. More often it looks almost fine, with one strip of missing bark running down the trunk, and the homeowner has no idea whether they are looking at a scar or a death sentence.

The honest answer is that it depends on the path the current took, and that you will not know for certain for one to two growing seasons.

What lightning actually does

The current follows the path of least resistance, which in a tree is the moist tissue just under the bark - the cambium and sapwood. It superheats the water in those cells, which flash to steam, and the steam blows the bark off from the inside. That is why strike damage shows up as a vertical strip of missing bark rather than a burn.

The damage pattern depends on which route the current took:

Down the outside, through the bark and cambium only. Best case. A narrow strip of damage, often on one side. The tree loses that strip of vascular tissue permanently but the rest keeps functioning. Many trees survive this.

Down through the sapwood on multiple sides. Worse. More of the water-conducting tissue is destroyed, and the crown above it may not get enough water next summer.

Down the center, through the heartwood. Worst, and often the one that looks the most violent - splits, blown-out trunk sections, bark scattered 50 feet away. The structural integrity of the stem is compromised.

Through the root system. The deceptive one. There may be very little visible trunk damage and substantial root damage, and the tree declines over the following two seasons for reasons nobody connects to the strike.

The first 48 hours

Keep people away from the tree. The hazard immediately after a strike is loose, hanging, and partially detached wood that may not be visible from the ground. Limbs can let go hours or days later. Keep cars out from under it and kids off the swing.

Look for the obvious emergencies. Anything leaning into a structure, hanging over a driveway, resting on a wire, or a trunk that is split through - those are same-day calls. See storm-damaged tree: what to do first and emergency tree service.

Photograph everything from several angles and distances, with date stamps. Lightning damage is a covered peril under most homeowners policies, and the before-cleanup photos are what the claim rests on. Does homeowners insurance cover tree removal covers what is and is not paid for.

Do not start cutting. Beyond moving a fallen limb that is blocking the drive, there is nothing useful a homeowner can do in the first two days, and plenty that is dangerous.

Do not apply wound dressing or paint over the damage. It traps moisture against compromised tissue and does not help. The tree compartmentalizes the wound on its own.

Reading the odds

What an arborist is actually assessing on a strike:

How much of the trunk circumference lost bark. This is the single most predictive measure. Damage to a narrow strip on one side - a survivable wound on a vigorous tree. Damage running more than about a third of the way around, or multiple strips on opposing sides, and the vascular system above it is in real trouble. A fully girdled stem is fatal, and it may take two years to prove it.

Whether the stem is split. A trunk split through the center is a structural failure, not a wound. These come down.

Where the damage is. A strike that ran down a major limb and stopped is a far better situation than one that ran the full length of the main stem into the root flare.

Species. Oaks, which are a large share of the North Shore canopy, tend to be comparatively resilient to strikes and are also the most commonly struck, being tall and often the highest point on a lot. Thin-barked species like beech and birch tend to fare worse.

Prior condition. A tree that was already stressed, decayed, or in decline does not have the reserves to wall off a major wound. A healthy vigorous tree sometimes does.

An arborist consultation is genuinely worth the money here, because the gap between "scar" and "hazard tree over the house" is the whole question and it is not obvious from the ground.

Then you wait

For a tree that is not an immediate hazard, the management plan is usually:

1. Remove the broken and hanging limbs - the actual safety work, done now.
2. Leave the wound alone. No paint, no sealant, no cutting back the bark to "clean it up."
3. Water it through dry spells for the next two summers. A tree with a reduced vascular system is drought-vulnerable in a way a healthy tree is not, and deep watering during August dry spells is the highest-value thing you can do.
4. Do not fertilize with high nitrogen. Pushing a stressed tree to produce growth it cannot support is counterproductive.
5. Look at it again next spring, and the spring after.

What you are watching for the following season:

• Does the crown leaf out fully, or is there a dead section directly above the damaged strip?
• Is there new callus tissue rolling in at the edges of the wound? That is the tree closing the gap, and it is the best sign there is.
• Secondary attack. Borers and decay fungi move into strike wounds. Sawdust, exit holes, or fungal conks appearing at the wound are a bad turn - see mushrooms at the base of your tree.
• Summer wilt or early fall color in the crown above the damage.

A tree that leafs out fully two springs running and is forming callus has probably made it. A tree that leafs out thin, then thinner, is on the way out, and the second year is usually when that becomes clear.

When it comes down

A lightning-damaged tree is a hazardous removal for a specific reason: you cannot trust the wood. Internal cracking from the steam expansion is often invisible from outside, which means a climber cannot assume a limb will hold, and a section may not behave the way sound wood behaves when it is cut. Crews treat these as unknown-integrity trees - which generally means rigging rather than climbing, or equipment rather than rigging.

That is also why lightning removals are frequently the case for a crane: nobody has to put weight on compromised wood. Large tree removal cost covers the ranges for a big specimen.

If the tree was worth protecting in the first place and a neighboring specimen is similarly exposed, lightning protection systems for trees are a real thing - a copper conductor run up the tree to a ground rod, the same principle as on a building. They are typically specified for high-value heritage trees near structures, and the cost is nontrivial. For a 200-year-old bur oak shading the house, it is sometimes an easy decision.

The short version

1. Keep everyone away from the tree for the first few days. Hanging wood is the immediate hazard.
2. Photograph before any cleanup. Lightning is a covered peril.
3. How much of the trunk lost bark is the question. One narrow strip is survivable. A third of the way around or a split stem usually is not.
4. Remove hazards now, then wait two growing seasons before deciding on the tree itself.
5. Water it through dry spells and leave the wound unpainted.

Big exposed oaks and maples on open North Shore lots in Winnetka, Lake Forest, Highland Park, Glencoe, and Northbrook are the ones that get hit. If lightning hit a tree on your property, request a free on-site estimate for an assessment of what has to come off now and what can wait.