A tree struck by lightning does not always die, and it does not always need to come down right away. What decides its fate is how much bark and wood the strike destroyed, not the fact that it got hit at all. A narrow scar on one side of the trunk is often survivable. A trunk that is split open or stripped bare around most of its circumference usually is not.
Boise and the rest of the Treasure Valley get their share of summer thunderstorms, especially the dry, fast-moving kind that roll off the foothills in July and August with more lightning than rain. If a tree in your yard took a hit, the next few weeks matter more than the first few minutes. Here is what actually happens inside the tree, what to check, and when the damage crosses over into a safety problem.
What lightning does inside a tree
Lightning does not just scorch the outside of a tree. Water and sap inside the trunk absorb the heat and flash into steam almost instantly, and that steam has nowhere to go but out. It blows bark and wood fiber away from the trunk from the inside, according to the Alabama Cooperative Extension System, which is why a lightning strike can look like an explosion rather than a burn.
The result ranges from a single narrow strip of missing bark to a trunk stripped bare on one side, with deep vertical cracks running through the wood underneath. Sometimes the damage runs down into the root system too, especially if the strike traveled to ground through a root that was closer to the surface than the rest.
Will the tree survive? What actually decides it
There is no reliable percentage to quote here, and any tree company that gives you one is guessing. Nebraska Extension puts it plainly: a lightning-struck tree, even one with little visible damage, may not survive, and only time will tell.
What extension foresters do point to is the size of the wound relative to the trunk. As a rule of thumb, bark loss that wraps less than about a third of the way around the trunk gives the tree a real shot at closing the wound and recovering with some care. Damage that strips a third or more of the circumference opens the tree to decay that spreads for years afterward, even if the tree technically lives. A trunk that is split lengthwise in multiple places, or a tree that is now leaning where it was not before, is a different situation: that is a structural problem, not a wait-and-see one.
What to check the same day
Do this from a safe distance first. If the strike also brought down a power line nearby, stay well back from the tree and the line, and call Idaho Power and 911 before you do anything else.
Once it is safe, look for:
- A stripped or shredded bark strip, and roughly how far around the trunk it wraps
- Vertical cracks in the trunk or major limbs, and how deep or long they run (a crack that opens and closes when you press near it, or one you can see daylight through, is a bigger deal than a surface split)
- Any new lean in the tree, or soil that looks heaved or cracked at the base, which can mean root damage
- Broken or hanging limbs anywhere in the canopy
If you find a vertical crack and are not sure how serious it is, our guide to reading a crack in a tree trunk walks through what depth and length actually mean for safety.
If the tree is leaning, has a limb hung up over something it could fall on, or the crack looks like it goes deep into structural wood, that is worth a same-day look rather than a wait. Call us at (208) 247-9766 or reach out through our contact form and we can tell you over the phone whether it sounds like something to get eyes on quickly.
Signs that show up in the days and weeks after
A lot of lightning damage is not obvious on day one. Nebraska Extension recommends waiting to see how the tree responds rather than making a removal decision immediately, since the full extent of internal damage often takes weeks or longer to show up on the outside.
Watch for:
- Wilting or browning leaves on part or all of the canopy, even with normal watering
- Bark that was loose or blown back starting to dry out, curl, and separate further from the wood
- Sap or sawdust-like debris collecting in bark crevices, a possible sign of insects moving in
- Any part of the crown that stops leafing out the following spring while the rest of the tree does
A tree that looks fine in September but drops a major limb or a section of canopy the following spring is a common pattern with lightning damage. If you are seeing several of these signs together, it is worth having someone classify how serious the damage actually is. Our hazardous tree removal guide explains how a tree gets called out as a hazard versus just cosmetically damaged.
The year after: bark beetles and other secondary threats
The strike itself is often not what kills the tree. Insects and disease moving into the wound over the following months usually do the real damage.
This is a bigger concern for pines than for most other trees in the valley. Bark beetles, including Ips beetle, target trees that are already stressed by drought, injury, or disease, according to University of Idaho Extension, and a fresh lightning wound is exactly that kind of injury. Watch for small holes in the bark oozing sap or packed with reddish boring dust, especially in the weeks after a strike. Our pine tree problems guide covers what healthy Boise pines should look like so you have something to compare against.
Hardwoods face a similar risk from wood-boring insects and decay fungi that get into the wound before it closes over. Keeping the tree watered through the rest of that growing season and avoiding any other stress, like heavy pruning or soil compaction near the roots, gives it the best odds of walling off the damage before something moves in.
Can a lightning-damaged tree be saved?
Often, yes, if the wound is on the smaller side and the trunk is still structurally sound. The usual first step is a tree health assessment to look at the wound, check for internal decay, and decide whether the tree is a save or a remove. That runs $75-$250 depending on the tree, and it is often waived if you go ahead and schedule the follow-up work. Our tree health assessment page explains what that visit actually covers.
For a trunk with a split union or a weak point that did not fully fail, cabling or bracing can sometimes hold things together for years rather than losing the tree or the limb outright. Systems typically run $200-$900 depending on the tree and how many points need support. Our cabling and bracing guide covers when that makes sense instead of taking a tree down.
If the tree does need to come down, cost depends heavily on height and how close it is to structures. For a rough sense of what removal runs in Boise, our tree removal cost calculator breaks it down by size rather than giving one flat number.
For trees that get hit repeatedly, or a single high-value shade tree you do not want to risk, lightning protection systems exist. A thin copper conductor is run from near the top of the tree down to a grounding rod, giving the strike a path to follow that is not through the trunk itself. It will not stop a tree from ever getting hit, but it changes what happens when it does. Ask about it if you have a tree that matters enough to protect this way.
When to get a professional look
Not every lightning-struck tree needs a visit. If the damage is a narrow bark strip and the tree is otherwise healthy, watching it through the next growing season is often the right call. But get it looked at if the tree is leaning, dropping large limbs, showing a deep trunk crack, or sitting within reach of your house, driveway, or a fence.
We offer free on-site estimates with no obligation, and our ISA-certified arborists can tell you whether a strike is something to monitor or something to act on. If a limb or the whole tree is already down or actively unsafe, we are available 24/7, including nights and weekends, with same-day response. Call (208) 247-9766 or reach out through our contact form, and if the tree is anywhere near a power line, call Idaho Power first and keep your distance until they clear it.
Frequently Asked Questions
How do I know for sure my tree was struck by lightning?
Look for a strip of missing or blown-back bark running down the trunk, often in a spiral or straight line, sometimes paired with a scorched smell right after a storm. A vertical crack that was not there before, wood debris scattered at the base, or a sudden partial wilt after a thunderstorm are all signs. If you did not see or hear the strike, the bark damage pattern is usually the clearest giveaway.
Will a tree struck by lightning definitely die?
No. Many trees survive, especially with a narrow strike that damages less than about a third of the trunk’s circumference. Wider or deeper damage carries a much higher risk of decline, but there is no set percentage or timeline that applies to every tree. The safest approach is watching it through the next growing season rather than assuming either outcome.
How long does it take for lightning damage to show up?
Some damage is visible immediately, like stripped bark or a split trunk. Other effects, like dieback in the canopy or bark beetle activity, can take weeks to a full year to appear. Extension foresters generally recommend waiting through at least one growing season before deciding a lightning-struck tree is a total loss.
Should I remove a lightning-struck tree right away?
Only if it is actively unsafe: a severe lean, a trunk split through structural wood, or major limbs hung up over a house, driveway, or walkway. Otherwise, most arborists recommend a wait-and-see period with basic care, since a tree that looks bad right after a strike sometimes recovers well.
Can lightning damage cause a tree to fail months or years later?
Yes. Decay can spread from an old lightning scar for years, weakening the trunk from the inside even after the tree looks fully healed on the outside. That is one reason a tree with a lightning scar is worth a periodic look rather than a one-time check.
Are pine trees more at risk after a lightning strike than other trees?
Pines face an added threat from bark beetles, which are drawn to trees weakened by fresh injury and can move in within days or weeks of a strike. A lightning-damaged pine is worth checking more often than a hardwood with a similar wound, since a beetle infestation can finish off a tree that the lightning itself did not kill.