Understanding Tree Defects, Likelihood of Failure, Targets, and Consequences
One of the most common statements we hear from property owners is:
“I’m worried this tree is dangerous.”
It’s an understandable concern. Large trees grow near homes, driveways, sidewalks, playgrounds, and businesses. After a severe storm or years of gradual decline, it’s natural to wonder whether a tree still poses an acceptable level of risk.
The challenge is that appearances can be misleading.
A tree that looks healthy may have significant internal decay. Conversely, a tree with visible cavities or old wounds may remain structurally sound for many years.
Professional tree risk evaluation is not about making quick judgments based on appearance. It is a systematic process that considers the tree, the site, and the people and property that could be affected if something were to fail.
What Is Tree Risk?
Many people assume tree risk is determined solely by the condition of the tree.
In reality, risk is a combination of several factors working together.
Professional arborists generally consider questions such as:
- What could fail?
- How likely is it to fail?
- What could it strike if it failed?
- What would the consequences be?
A defect by itself does not automatically create unacceptable risk.
For example, a large dead branch over a rarely used pasture presents a different level of concern than the same branch hanging over a child’s playset.
The surrounding environment matters just as much as the tree itself.
Tree Defects Are Only One Piece of the Puzzle
During an evaluation, an arborist may observe conditions such as:
- Dead branches
- Cavities
- Decay
- Included bark
- Cracks
- Codominant stems
- Root damage
- Leaning stems
- Fungal fruiting bodies
- Previous storm damage
These observations help us understand the tree’s condition.
However, they do not automatically determine whether removal is necessary.
Instead, they help answer a larger question:
How do these conditions affect the tree’s ability to safely remain in the landscape?
Understanding Targets
A tree standing alone in an open field may have significant structural defects but present very little practical risk because there are few meaningful targets beneath it.
Now imagine that same tree growing beside:
- A home
- A driveway
- A school
- A playground
- A busy sidewalk
- Outdoor seating
- A parking lot
The condition of the tree hasn’t changed.
The consequences have.
This is why arborists spend time evaluating the site—not just the tree.
Likelihood Matters
Not every defect is equally concerning.
Professional evaluations consider the likelihood that a particular part of the tree may fail within a reasonable inspection period.
Some conditions remain stable for many years.
Others change rapidly.
For example:
A small pruning wound may close naturally over time.
A rapidly expanding crack through a major trunk may require immediate attention.
Experience, accepted arboricultural principles, and, when appropriate, advanced diagnostic testing help arborists evaluate these situations objectively.
Consequences Matter Too
Imagine two identical branches.
Both have similar defects.
Both have the same likelihood of failure.
One hangs over an unused portion of a wooded property.
The other hangs directly over the front entrance of a daycare.
The likelihood may be identical.
The consequences are not.
Tree risk is always evaluated within the context of the site.
Managing Risk Doesn’t Always Mean Removing the Tree
One of the biggest misconceptions in tree care is that every concern requires removal.
In many cases, risk can be reduced through appropriate management.
Examples include:
- Structural pruning
- Removal of dead branches
- Crown reduction
- Supplemental support systems
- Root-zone improvements
- Construction protection
- Target management
- Periodic monitoring
Sometimes a simple change in how an area beneath a tree is used can significantly reduce overall risk without removing the tree.
Every situation is unique.
When Advanced Diagnostics May Help
Visual inspection provides valuable information, but occasionally additional information is needed.
Advanced diagnostic tools may help answer important questions when visual observations alone are not enough.
Depending on the situation, this may include:
- Sonic tomography
- Resistograph testing
- Root investigations
- Root collar excavation
- Air spading
- Soil evaluations
These technologies do not replace professional judgment.
They provide additional measured information that helps support well-informed management decisions.
Tree Risk Changes Over Time
A tree is not static.
Weather, construction, drought, insects, disease, root disturbance, and normal growth all influence its condition.
For that reason, a tree that presents an acceptable level of risk today may require re-evaluation in the future.
Periodic inspections are particularly valuable for:
- Mature trees
- Historic trees
- Trees near homes
- Commercial properties
- Schools
- Parks
- Homeowner associations
- Trees with known structural concerns
Regular evaluations allow management decisions to be made before problems become emergencies.
Our Approach
At Davis Family Arbor Services, tree risk evaluations are based on careful observation, accepted arboricultural practices, and the specific conditions present at the time of inspection.
Every recommendation considers:
- The condition of the tree
- Site conditions
- Potential targets
- The property owner’s objectives
- Available management options
Sometimes preservation is appropriate.
Sometimes pruning reduces risk.
Sometimes continued monitoring is recommended.
Sometimes removal becomes the most appropriate management option.
Every recommendation is based on the individual tree—not assumptions or appearances.
Final Thoughts
Trees are living organisms that continue to grow and change throughout their lives.
Understanding tree risk requires looking beyond visible defects and considering the entire picture.
A thoughtful evaluation can help property owners make informed decisions that balance safety, tree health, long-term value, and management objectives.
The goal isn’t simply to identify problems.
The goal is to identify the most appropriate solution.
About the Author
Brad Davis is an ISA Board Certified Master Arborist® (MW-6328B), ISA Tree Risk Assessment Qualified (TRAQ) professional, and ISA Florida Chapter Prescription Pruning Qualified (PPQ) arborist. He provides science-based arboricultural consulting, tree preservation planning, advanced diagnostics, tree risk assessments, construction tree protection, and professional tree care throughout the Tulsa metropolitan area.
