An arborist’s assessment is the foundation of any good tree care decision. Done correctly, it tells you whether a tree is healthy or declining, whether it presents a hazard and at what level of risk, and what intervention — if any — is warranted. Done incorrectly (or by someone without the training to do it), it’s an opinion dressed as expertise. Knowing what a proper assessment includes is what lets you evaluate whether the one you’re getting is real.
“The most valuable thing I do for homeowners is tell them their tree doesn’t need to come down. I do that probably 40 percent of the time when I’m called out for a tree a homeowner is worried about. A tree removal company makes money removing trees. An independent arborist makes money giving you accurate information. Those are different incentives, and they lead to different recommendations.”
— Tomasz Kwiatkowski, ISA Certified Arborist and tree risk assessment qualified practitioner with 20 years of experience in residential and municipal tree management in the local area
Table of Contents
Questions About the Assessment Process
What does a tree health assessment include?
A professional tree health assessment examines:
Crown condition: Foliage density, color, and distribution. Dead or dying branches. Signs of stress (chlorosis, marginal leaf scorch, early leaf drop).
Structural defects: Included bark (where two stems grow together, sometimes creating a weak union), cracks and cavities, decay and fungal fruiting bodies (conks), root damage, previous poor pruning.
Root zone condition: Soil compaction, grade changes, construction damage, root conflicts, signs of root decay.
Lean and lean history: Degree and direction of lean, whether it appears to be longstanding (likely stable) or recent (potentially indicating root or structural failure).
Target identification: What is beneath and around the tree — structures, utility lines, vehicles, pedestrian areas — that would be affected if the tree or a part of it failed.
Ask the arborist to walk you through each of these elements for your specific tree.
Who is conducting this assessment, and what are their qualifications?
Ask specifically:
- Is the person conducting the assessment an ISA Certified Arborist?
- Are they also ISA Tree Risk Assessment Qualified (TRAQ)? TRAQ is an additional credential for formal hazard and risk assessment.
- Can you provide your certification number for verification at isahq.Org?
What a good answer looks like: An ISA Certified Arborist, ideally with TRAQ qualification for hazard assessment, with a verifiable certification number.
Will the assessment result in a written report?
For any tree where safety is the question, ask for a written report. The report should:
- Identify the species
- Describe the tree’s condition in each assessment category
- Identify any specific defects and their significance
- Assess the likelihood of failure
- Identify the consequences if failure occurs
- State the overall risk level
- Make specific recommendations
A verbal opinion is not sufficient if you’re making a significant decision (removal, major pruning, filing an insurance claim, or documenting a hazard situation before an event occurs).
Questions About Risk Assessment
What is the tree risk assessment methodology being used?
The ISA has published a formal Tree Risk Assessment methodology — the Basic or Advanced level of the TRAQ (Tree Risk Assessment Qualification) framework. This provides a standardized approach to evaluating:
Likelihood of failure: How likely is the tree or a specific part to fail under normal or storm conditions?
Likelihood of impact: If it fails, how likely is it to hit the target (structure, vehicle, person)?
Consequences: What would happen if it did hit the target? (A branch falling on a garden shed vs. a tree falling on an occupied bedroom are very different consequences.)
Overall risk rating: Low, moderate, high, or extreme — based on combining the above factors.
Ask whether the assessment uses the ISA TRAQ methodology and whether the assessor is TRAQ qualified.
What specific defects were identified, and how significant are each?
Ask the arborist to explain each defect they’ve identified:
- What is this defect? (E.g., included bark at a co-dominant stem, decay in the root crown, a crack in the main stem)
- What does it mean for the tree’s structural integrity?
- Is this defect progressing (getting worse) or stable?
- Does this defect warrant treatment, monitoring, or immediate removal?
An arborist who can explain each defect clearly — in plain language, with a rationale for their recommendation — is giving you a real assessment. One who says “the tree is dangerous” without identifying specific defects is giving you an opinion without evidence.
Is this defect the cause for removal, or can it be managed?
Not every defect necessitates removal. Ask specifically whether the defect identified could be managed through:
- Pruning: Removing a structurally compromised co-dominant stem, reducing crown weight on the side toward the target
- Cabling and bracing: Installing flexible cables between major stems to limit movement and reduce failure risk for specific structural defects
- Treatment: Fungicide or other treatment for specific diseases
- Monitoring: Annual or seasonal re-assessment without immediate intervention
If the arborist recommends removal, ask specifically why these alternatives are not appropriate. A good answer names the defect and explains why it can’t be adequately mitigated.
Questions About Tree Species and Conditions
Is this tree likely to fail sooner given the species?
Some species are structurally weaker than others and more prone to specific failure types:
Silver maple (Acer saccharinum): Very fast-growing, prone to included bark and branch failure. Common in many regions yards.
Some regions maple (Acer negundo): Fast-growing, brittle, often multi-stemmed with included bark.
Willows: Generally short-lived, weak wood, prone to storm damage.
Honeylocust: Generally stronger wood, but thorns and pods create management issues.
Ask the arborist to assess your specific tree in the context of its species’ known failure tendencies.
What is the tree’s likely remaining useful life?
An arborist can give you a professional opinion about how long a tree in its current condition is likely to persist without major intervention. This matters for financial planning — a tree with 5 years of remaining life warrants a different investment in pruning than one with 30.
Related Questions
- Questions to Ask a Tree Service or Arborist Before You Hire One
- Questions to Ask When Getting a Tree Service Quote
- Do I Need a Permit to Remove a Tree in many regions?
- Red Flags When Hiring a Tree Service or Arborist
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