When to Call an Arborist

People use the word "arborist" loosely. Someone trims your hedges and they call themselves an arborist. A guy with a chainsaw and a pickup truck puts "arborist" on his business card. But a real certified arborist is something specific — and there are situations where having one on your side is worth every penny. Here is when you actually need one, what they do, and how to find a legitimate one in Massachusetts.

What an Arborist Actually Is

A certified arborist is not just someone who cuts trees. An ISA (International Society of Arboriculture) certified arborist has passed a comprehensive exam covering tree biology, soil science, diagnostics, safety, and management. They maintain their certification through continuing education. Think of them as tree diagnosticians — like a doctor for trees.

There is an important distinction between a consulting arborist and a tree service company. A consulting arborist assesses, diagnoses, and recommends. They typically do not do the physical tree work themselves. A tree service company (like McDonald Tree Service) does the actual removal, pruning, and grinding. We work alongside arborists regularly. They diagnose the problem and write the prescription. We fill the prescription.

When You Should Call an Arborist

1. Before Major Construction Near Trees

This is the number-one situation where an arborist can save you thousands of dollars and irreplaceable trees. If you are planning an addition, driveway expansion, pool installation, or any construction that comes within the dripline of a large tree, get an arborist assessment first.

An arborist can establish a tree protection zone, specify how close equipment can operate, recommend root pruning protocols if trenching is unavoidable, and identify which trees are most vulnerable. I have seen homeowners in Lexington, Carlisle, and Westford spend $200,000 on a renovation and then watch a $50,000 tree die three years later because nobody thought to protect the root zone during construction. A $300 to $500 arborist consultation before construction starts is cheap insurance.

2. When a Tree Looks Sick But You Do Not Know Why

If your tree has yellowing leaves, thinning canopy, dieback, or other signs of decline but you cannot pinpoint the cause, an arborist can diagnose the specific problem. Is it a nutrient deficiency? Fungal disease? Root damage from that sewer repair two years ago? Insect infestation? The treatment depends entirely on the diagnosis, and getting it wrong means wasting money on the wrong solution while the tree continues to decline.

An arborist will examine the foliage, bark, root zone, and surrounding site conditions. They may take soil samples, leaf samples, or core samples from the trunk. They can tell you definitively what is wrong and whether treatment is likely to succeed. Compare that to a fertilizer salesman who shows up and says every tree needs deep root fertilization.

3. For Insurance Disputes About Tree Hazards

If your insurance company is pressuring you to remove a tree they consider hazardous, or if a neighbor's tree damaged your property and you need documentation, an arborist's written assessment carries real weight. Insurance adjusters and attorneys recognize ISA-certified arborist reports as professional opinions. Our assessment as a tree service company does not carry the same credibility in a legal or insurance context because we have a financial interest in performing the removal.

Similarly, if your town is requiring tree removal or if there is a dispute with a neighbor about a boundary tree, an arborist's written report can support your position with the tree warden, planning board, or in small claims court.

4. For Large, Valuable Trees You Want to Preserve

If you have a heritage tree, a specimen tree that defines your property, or a tree with significant sentimental value, investing in an arborist consultation for a health care plan is smart. A consulting arborist can develop a multi-year management plan that includes pruning schedule, soil management, pest monitoring, and preservation strategies.

I have customers in Bedford and Lexington with 200-year-old oaks and maples that are irreplaceable. Those trees are worth tens of thousands of dollars in property value. A $500 annual arborist consultation to keep them healthy is one of the best investments those homeowners make.

5. When You Need a Written Tree Risk Assessment

A formal tree risk assessment (TRA) is a specific protocol defined by the ISA for evaluating the likelihood and consequences of tree failure. It considers the tree's condition, its targets (what it would hit if it fell), and the likelihood of failure. The output is a risk rating and specific recommendations.

Situations that call for a formal TRA include:

• A tree that is potentially hazardous but you are not sure whether it needs to come down
• Pre-purchase property assessment (you are buying a home with large trees and want to know their condition)
• Municipal or HOA requirements for tree work documentation
• Liability concerns about trees near public areas, walkways, or parking

What Happens During a Tree Risk Assessment

Here is what a thorough arborist assessment actually involves:

Visual Inspection (Level 1 and Level 2)

The arborist walks the property and examines each tree from the ground. They look at canopy condition, bark integrity, trunk structure, root zone, lean, and site factors (drainage, soil conditions, proximity to targets). A Level 1 assessment is a walk-by survey of multiple trees. Level 2 is a detailed individual tree assessment with a closer look at specific concerns. Most residential consultations are Level 2.

Sounding

The arborist taps the trunk with a mallet and listens to the sound. Solid wood produces a sharp, resonant sound. Hollow or decayed wood produces a dull thud. This is a quick, non-invasive way to detect internal cavities and decay without cutting into the tree.

Resistance Drilling (When Needed)

For trees where internal decay is suspected but the extent is unclear, the arborist may use a resistance drill (Resistograph). This tool drills a thin needle into the trunk and measures the resistance as it passes through the wood. It produces a graph showing exactly where sound wood, decay, and cavities are located. It creates a hole smaller than a pencil and does not harm the tree. This is the gold standard for quantifying internal decay.

Root Zone Evaluation

The arborist examines the visible root zone for signs of decay, severed roots, soil heaving, and grade changes. In some cases, they may use an air spade to excavate soil from around the root flare without damaging roots, which reveals girdling roots, buried decay, and other problems hidden below grade.

Written Report

A good consulting arborist provides a written report documenting their findings, risk rating, and specific recommendations. This report is the primary deliverable. It is what you use for insurance claims, municipal permits, construction planning, and your own decision-making.

How to Find a Legitimate Arborist in Massachusetts

Here is what to look for:

• ISA certification: Look for the ISA Certified Arborist credential. You can verify certification at the ISA website (treesaregood.org). The ISA also has a "Find an Arborist" search tool.
• Massachusetts Certified Arborist License: Massachusetts requires a license for anyone performing commercial tree work. The license is issued by the Department of Conservation and Recreation.
• TRAQ qualification: For tree risk assessment specifically, look for an arborist with the ISA Tree Risk Assessment Qualification (TRAQ). This is an additional credential beyond basic certification that specifically covers hazard assessment methodology.
• Consulting vs. commercial: If you need an independent, unbiased assessment, look for a consulting arborist who does not sell tree work services. Their recommendation has no financial conflict of interest. The American Society of Consulting Arborists (ASCA) maintains a directory of qualified consultants.
• Insurance and references: Verify liability insurance and ask for references from similar assessments. A good arborist is happy to provide both.

What an Arborist Assessment Costs

Expect to pay $300 to $600 for a thorough residential consultation with a written report. Complex assessments involving multiple trees, resistance drilling, or legal documentation may run $600 to $1,000+. A quick verbal consultation without a written report may be $150 to $300. These numbers are typical for Middlesex County in 2026.

Is it worth it? If the assessment saves a $30,000 tree, prevents a $50,000 damage claim, or gives you peace of mind about the 60-foot oak over your bedroom, absolutely.

How We Work With Arborists

McDonald Tree Service does removal, pruning, and stump grinding. We are very good at it, and we have been doing it since 1995 across Billerica, Chelmsford, Tewksbury, Lowell, Wilmington, and 8 other towns in our service area. What we do not do is sell diagnostic services or treatment plans. When a tree needs diagnosis beyond what an experienced visual assessment can provide, I tell my customers to consult a certified arborist.

The arborist determines what the tree needs. If it needs pruning, we prune it to their specification. If it needs to come down, we remove it safely. If it needs health care treatment, the arborist either provides it or recommends a plant health care company. It is a system that works because everyone stays in their lane.

If you are not sure whether you need an arborist or a tree service, start by calling us at (978) 375-2272. I will take a look and tell you honestly whether it is something we can handle or whether you need an arborist's expertise first. No charge for that conversation. Read our tree health inspection guide for what you can check yourself before making any calls.