Is a hollow tree dangerous?
An open cavity in the trunk or a major limb, soft crumbling wood you can push a tool into, or a trunk that sounds hollow when you knock on it.
Not an emergency this afternoon, but the window for a useful response is measured in weeks. Left alone, most of these get more expensive rather than less.
Not automatically, and the reason is structural rather than optimistic: a tree carries its load in the outer shell of wood, the same way a steel pipe is nearly as strong as a solid rod of the same diameter. What matters is how much sound wood remains around the hollow, how much of the circumference is open, and what stands underneath. A hollow tree over open lawn and the same tree over a bedroom are two different conversations.
What this looks like
Cavities usually start where a large limb was lost or a wound was never closed over. Some are small pockets that the tree has walled off and grown around, with a thick rolled edge of callus showing that it is winning. Others open into a chamber you can put an arm into, with soft brown or white punky wood inside. The rolled callus edge is a good sign. Soft wood extending outward toward the bark, and a thin remaining wall, is not.
- A thick, rolled ridge of callus growing in around the opening
- Wood inside that is soft, stringy, brown-cubed, or white and spongy
- A hollow, drum-like sound when the trunk is tapped, compared with the solid thud higher up
- Fungal conks, wet staining, or insect activity at the cavity margins
What causes it in Kansas
Roughly in order of how often each turns out to be the answer here. The line under each one is what separates it from the others — open a cause for the detail.
1Decay following a wound
How to tell: The cavity lines up with an old limb loss, a stub, or a scar.Storm breaks, bad pruning cuts, mower damage, and lost limbs all open a path into the trunk. Decay fungi enter, consume heartwood, and hollow the interior over years while the tree keeps growing new wood on the outside.
2Old topping cuts
How to tell: A flat-cut stub high in the tree with sprouts around it, and decay tracking down the stem below.A cut through a large stem leaves a wound the tree cannot close, and decay runs down the interior from it. Trees topped in the eighties and nineties across Kansas are the ones hollowing now.
3Heart rot fungi
How to tell: A full, green crown on a trunk that sounds hollow — the combination that surprises people most.Species that specialize in the non-living heartwood at the center of the trunk. The tree can look perfectly healthy while the core is consumed, because heartwood is structural rather than living tissue.
4Butt rot rising from the roots
How to tell: Conks or mushrooms on the root flare, soft wood at the base, and sometimes soil cracking near the trunk.Root and butt rot fungi work upward from the root plate into the base of the trunk. This is the most serious version, because it degrades the wood exactly where bending stress is highest.
5Animal enlargement
How to tell: A smoothed, worn entrance with fur, feathers, or nesting material, in a cavity that was already there.Raccoons, squirrels, owls, and woodpeckers enlarge existing cavities. They are not the cause of the hollow and their presence says nothing about the tree's strength either way.
What to do, and what to avoid
Safe to check yourself
All from the ground — no ladder, no saw.
- Measure the opening's width and the trunk's circumference at that height, and write both down
- Tap around the trunk with a rubber mallet, listening for the change from solid to hollow
- Look for conks anywhere on the trunk or root flare, which changes the assessment substantially
- List what is inside the fall zone: house, drive, sidewalk, play set, or nothing at all
What not to do
The responses that make this one worse or permanent.
- Do not fill the cavity with concrete, expanding foam, or gravel — it traps moisture, abrades the wood as the tree moves, and hides everything an inspection needs to see
- Do not dig, scrape, or 'clean out' the decayed wood, which breaks down the barrier zones the tree built to contain it
- Do not seal or paint the opening
- Do not judge the tree by its crown alone, since a fully leafed canopy is entirely compatible with serious internal decay
When to contact an arborist
Want a professional verdict in the Wichita area?
A tree in this condition is a judgment call that has to be made standing next to it. Kohnen's Tree Service provides on-site assessments, removals, and stump grinding across Wichita and the surrounding communities.
When a situation calls for professional help in the Wichita area, we refer readers to Kohnen's Tree Service, a working Kansas tree-care company whose field experience informs this site. That relationship is disclosed here and on our About page.
Whatever this narrows it down to, the assessment that decides what happens next has to happen at the tree. Why that is
Common questions
How much hollow is too much?
How much hollow is too much?
Arborists commonly start paying close attention when the remaining sound wall is less than about a third of the stem's radius, or when an open cavity exceeds roughly a third of the circumference. Both are screening thresholds that trigger a closer look — not a formula that decides removal, because loading, lean, crown size, and what stands below all enter the judgment.
The tree looks completely healthy. How can it be a risk?
The tree looks completely healthy. How can it be a risk?
Health and structure are separate questions. Foliage is produced by the thin living layer just under the bark, which can be entirely intact over a hollow core. Trees with full, green canopies fail from decay every storm season in Kansas.
Should hollow trees always be removed?
Should hollow trees always be removed?
No. Plenty of hollow trees stand for decades and are valuable wildlife habitat. Removal becomes the reasonable call when the sound wood is too thin for the load, decay is in the roots or base, or the consequences of failure are unacceptable — which is exactly the judgment an on-site assessment produces.
Kansas Tree Guide is an independent educational resource. Nothing on this site replaces an on-site assessment by a qualified arborist or tree-care professional. Last reviewed August 2026.
Often seen alongside this
A second symptom narrows the cause faster than more detail about the first.
Not what you are seeing? Work the symptom guide again.