April 21

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What Causes a Tree Trunk To Become Hollow?

By Dennis Shea

April 21, 2026

tree services, tree services in Thornton CA

Are you worried about a hollow tree trunk in your yard? As the go-to crew for tailored tree services in Thornton, CO, we at Arbortec Tree Service have diagnosed our fair share of unusual arboreal issues. Read on to learn the common reasons for hollow tree trunks.

Is Your Tree Structurally Compromised?

Before getting up close, take a good look at your specimen from a distance. Watch out for the following red flags:

  • A hole in the trunk that looks moist and rotten
  • Large cracks or splits in the trunk
  • A noticeable lean or tilt in the tree
  • Sparse, discolored foliage
  • Severe branch dieback
  • Fungi or mushroom growth at the base

Contact an arborist as soon as you spot any of the above issues. They know how to safely evaluate the tree, address potential hazards, and recommend ways to save it when possible.

Common Causes of Tree Trunk Decay

What causes a tree trunk to become hollow? This problem is often the result of damage, such as a wound or a broken branch, that allows pathogens to take hold. Over time, the decay may expand, creating a noticeable hole. The tree eventually isolates this rotted area through a process called compartmentalization, and new wood may continue to grow around the hollow, but that doesn’t mean you can just ignore it.

Below are some common culprits to consider.

Human Activity

Sometimes, we unknowingly contribute to a tree’s internal damage. Improper pruning, accidental scrapes from lawn mowing equipment, or driving nails into the trunk to hang decorations create potential entry points for decay.

Weather Damage

Nature can be relentless. Storms with high winds, lightning strikes, and heavy snow can cause cracks or splits in trunks. It never hurts to assess your trees after a bout of bad weather.

Insects

Carpenter ants, bark beetles, termites, and other wood-boring insects create tunnels in trees to lay eggs and build nests. These activities weaken the tree’s structure and make it vulnerable to hollow formations.

Wildlife Creatures

Woodpeckers, squirrels, and even raccoons may see your tree as their perfect home. While it’s fascinating to spot critters in your yard, their activity can compromise its integrity. Continuous pecking or nesting may create small wounds, which can expand into larger, problematic cavities.

Are Tree Trunk Holes Dangerous?

Now that you know how decay leads to hollow trees, should you do something about it? Most cavities are harmless and don’t require attention.

Take the time to assess your specimen. If it looks fairly lush and healthy, and the hole seems fairly small and fully healed over, it’s likely fine. A large cavity that compromises the internal structure or actively spreading decay may warrant a professional checkup.

Dependable Tree Specialists in Thornton

With so many factors that can make trees hollow inside, pinpointing the cause on your own might prove tricky. That’s where Arbortec Tree Service comes in.

We’re here to assess and treat hollow tree trunk issues, so your living landscape stays healthy and thrives beautifully. Contact us today, or explore more of our blog to learn the importance of tree risk assessments.

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