The Hollow Inside: Is Your Tree a Silent Hazard?

Trees are the stoic guardians of our landscapes. They provide shade, boost property value, and look great doing it. But there is a darker side to tree health that many homeowners miss until it’s too late. It’s called heart rot, and it allows a tree to look perfectly healthy on the outside while the interior is structurally crumbling.

If you’ve ever looked at a massive tree and wondered, "Is that thing going to fall on my house?"—this guide is for you. We’re going to look at how to play tree detective and what to do if your suspicions are confirmed.

1. Understanding the Anatomy: Why "Hollow" Happens

To understand rot, you have to understand how a tree is built. Think of a tree like a series of nested straw-like tubes.

Sapwood (Outer layers): This is the living tissue. As long as this layer is healthy, the tree will have green leaves and look "fine."
Heartwood (The center): This is the "bones" of the tree. It is dead tissue that provides the structural pillar for the tree to stand upright.

Heart rot occurs when fungi enter the tree through a wound and eat that dead heartwood. Because the sapwood is still working, the tree keeps growing leaves, masking the fact that its "bones" are turning into mush.

2. Five Visual Clues You Can’t Ignore

A. The "Fruiting Bodies" (Mushrooms)

If you see mushrooms growing out of the trunk (conks) or at the base, it's a major red flag. These are the visible reproductive parts of the decay fungi already eating the tree from the inside.

B. Visible Cavities and "Animal Condos"

If an animal has made a home in a hole, the rot has already breached the tree's internal defenses. While charming, these holes are clear evidence of structural loss.

C. Co-Dominant Stems

Does your tree split into two main trunks that look like a "V"? Moisture trapped in that "V" often leads to internal rot right at the most critical stress point of the tree.

3. The Big Question: Remove or Keep?

Not every hollow tree needs to be cut down. Many hollow trees can stand for decades! Arborists use the Rule of One-Third:

If the "shell" of healthy wood is at least 30% to 35% of the tree's total radius, it is likely stable.
If the rot is more extensive, the risk of "buckling" during high winds becomes dangerous.

PRO TIP: If the tree is in an open field, leave it for wildlife. If it's within falling distance of your house, car, or power lines, you have a "high-target" situation that requires immediate action.

4. How to Handle Removal

If you've determined the tree has to go, you have two paths: DIY or Professional. Here is the honest truth about both.

The DIY Approach (Only for Small Trees)

If the tree is under 10-15 feet tall and far away from structures, you might handle it yourself. But beware: rotted trees do not fall like healthy trees.

Brittle Wood: Rotted wood is unpredictable. It can "snap" or "shatter" before your cut is even finished.
The "Barber Chair": Hollow trees are prone to splitting vertically and kicking back toward the sawyer—a deadly phenomenon called a barber chair.
Hidden Weight: Rot can make one side of the canopy much heavier than the other, causing the tree to twist as it falls.

When to Call a Professional (Non-Negotiable)

You should NEVER attempt to remove a rotted tree yourself if:

The tree is taller than 20 feet.
The tree is leaning toward a structure or power line.
The trunk is visibly "oozing" or has massive cavities at the base.
You aren't 100% confident in making a "bore cut" (a specialized technique for hollow trees).

Bottom Line: A rotted tree is a liability. It’s much cheaper to pay for a controlled removal today than to pay for a new roof (and an emergency crane crew) after a storm next week.