Through a formal plant appraisal, which is a recognized professional process rather than a rough guess. Arborists appraise trees using the Council of Tree and Landscape Appraisers Guide for Plant Appraisal, published by the ISA, which sets out accepted methods for putting a defensible dollar figure on a tree. The most common for a large specimen is the trunk formula technique, which builds a value from the tree’s trunk size and a regional cost basis and then adjusts it for the tree’s condition, species and location on the property. A big, healthy, well-placed tree on a McLean lot can carry a substantial appraised value, and because the method is standardized and documented, the number holds up when someone, an insurer, a court, an assessor, asks how it was reached.

Yes, and that is one of the main reasons appraisals exist. When a storm destroys or badly damages a mature tree, a claim often turns on a credible value for what was lost, and a written appraisal prepared by a qualified arborist to the recognized plant-appraisal standard is what supports it. The report documents the tree’s size, species, condition and location and shows how the value was calculated, which is exactly what an insurer needs to see rather than a homeowner’s estimate. On McLean properties, where a single specimen can represent real value, having that documentation prepared properly can make a meaningful difference to how a claim is resolved.

Sometimes, and it hinges on the rules more than on the tree. A casualty loss for damaged trees is generally measured by the decrease in the property’s fair market value, substantiated by a qualified appraisal, which an arborist’s plant appraisal can support. The important caveat is that since 2017 the personal casualty-loss deduction has been limited to losses in federally declared disaster areas, so it is not available for an ordinary storm that was not federally declared. That makes this squarely a question for a tax professional rather than something to count on, but if a deduction is potentially available, the documented appraisal is the piece the arborist provides. We can value the loss; whether it is deductible is your accountant’s call.

With a formal tree risk assessment, because a big tree over a high-value house is precisely the high-consequence situation that method is built for. Assessing to the ISA approach means weighing how likely the tree, or a specific part of it, is to fail, how likely a failure is to actually strike the house, and how severe that impact would be. A large specimen close to a home scores high on consequences, so the assessment focuses hard on the tree’s structure, any decay or defective unions, and its root condition. The valuable outcome is that this often justifies keeping the tree rather than removing it: targeted work such as crown reduction to lower the load, or cabling to support a weak union, can bring the risk down to an acceptable level while preserving a tree that would cost a great deal and many decades to replace.

They answer completely different questions. An estimate tells you what a piece of work will cost, pruning this tree, removing that one. An appraisal tells you what the tree itself is worth as an asset, calculated to a recognized professional standard and written up so it stands on its own. You ask for an estimate when you are deciding whether to hire the work. You ask for an appraisal when a dollar value on the tree matters to someone else, an insurer settling a claim, a court hearing a dispute, an assessor, or a property owner weighing a loss. On a McLean property with significant specimen trees, the two are genuinely separate services, and confusing them is why some homeowners are surprised that valuing a tree is a distinct, documented piece of work.

It does, mainly through the soil and the roots rather than the canopy. Properties backing onto McLean’s stream valleys often have trees growing on moist, sometimes sloping ground, and that changes what an assessment has to look at. The concern on this kind of lot is frequently the root plate and the base of the tree rather than only the crown, because a tree that looks completely sound above can lose its footing when saturated or eroding soil stops holding it. We look at whether the root flare is exposed, whether the downhill side is being undercut, and whether a lean has changed over time. It also means the trees along that wooded margin grew as part of a stand and can be more exposed once surrounding trees come out, which is worth weighing before removing any of them.