Understanding Internal Tree Decay and Hollow Trunks
Internal tree decay is a natural process that can occur when fungi enter a tree through wounds, broken branches, root damage, or other openings. Over time, fungi break down the tree’s internal wood, creating soft, weakened, or hollow areas while the outer trunk may continue to appear healthy.
The photographs above show extensive internal wood decay and a large cavity within a tree trunk. This type of deterioration can reduce structural integrity and increase the potential for trunk failure, particularly when combined with cracks, a compromised root collar, a heavy crown, or significant exposure to wind.
How We Evaluate Tree Decay
At Secured Arbor, we evaluate trees with suspected internal decay by examining the trunk, root flare, crown, visible defects, and surrounding property to make sure they are secured for your property. Where appropriate, we use sounding and probing techniques to help assess the condition of the wood. Advanced diagnostic equipment may be recommended when the extent of internal decay cannot be determined through a visual inspection alone.
Our evaluation considers the amount of remaining sound wood, the location and size of the cavity, the tree’s overall health and stability, and the potential targets beneath or near the tree.
Depending on the findings, we may recommend monitoring, corrective pruning, structural mitigation, or tree removal when necessary to reduce the risk to people and property.
If you suspect internal decay or a hollow trunk on your property, contact Secure Arbor for a professional tree assessment.
The photos show advanced internal wood decay with a large hollow cavity. This is commonly associated with fungal decomposition of the tree’s heartwood. The outer wood may remain intact while the interior becomes soft, fibrous, and structurally compromised.
How this happens
- Internal wood decay begins
Fungi enter through wounds, broken branches, root damage, or other openings and gradually break down the tree’s internal wood.
- A cavity develops
As decay progresses, the interior becomes hollow or filled with crumbly, decomposed wood. The remaining outer shell may still appear relatively healthy.
- Structural strength decreases
The loss of internal wood can reduce the tree’s ability to withstand wind, weight, and other stresses. The level of risk depends on the remaining sound wood and the tree’s location.
How to evaluate a tree with internal decay
As a Maryland Certified Tree Expert, you can use the following process when assessing a tree with a suspected cavity.
Tree decay assessment checklist
Inspect the tree’s exterior. Look for cavities, fungal fruiting bodies, cracks, old wounds, dead branches, and evidence of root or trunk damage.
Determine the cavity’s location and size. Record its height, width, depth, and orientation. A cavity near the base or a major branch union deserves particular attention.
Evaluate the remaining sound wood. Use careful sounding and probing where appropriate. Advanced assessment may require resistance drilling or sonic tomography.
Inspect the root flare and root collar. Look for decay, hollow areas, root damage, soil changes, and signs of instability.
Assess the tree and its surroundings. Consider species, lean, crown condition, wind exposure, and nearby targets such as homes, vehicles, roads, and people.
Determine the appropriate recommendation. Depending on the findings, options may include monitoring, pruning, mitigation, or removal.
The photographs alone cannot establish the exact fungal species, the full extent of decay in a standing tree, or whether removal is necessary.