How Arborists Observe Trees

Trees can make a lovely addition to your landscape, but they often come with their own set of risks. To ensure that your property is safe, personally inspect your trees every year. If you have large trees next to your house, hire an Arborist every two years to perform a site inspection. We also recommend an Arborist inspection before any tree removal or pruning of a tree with questionable health before. This prevents removing a possibly healthy tree or tree pruning that might prove fruitless.

A formal risk assessment, performed by an arborist, is the best way to guarantee your trees are safe. The arborist will check your trees for risk and health. The assessment is based on ANSI A300 Standards, Part 9. During the assessment, the arborist will observe your trees, identify defects, then judge how likely that defect is to cause tree failure.

Methods of tree assessment:

Light Observation:

This is just a basic overview of your tree and its health. The arborist will observe the tree from all available angles. This includes viewing the tree and the site in relation to any structures. Observing the tree is not as detailed as a tree risk assessment. The perceived risk in relation to any structures is the primary focus with light observation.

Tree Risk Assessment:

This is a detailed assessment of a tree or group of trees. Arborists view soil conditions, growth patterns, soil moisture, wind patterns, and other factors. Using a checklist, an Arborist will note defects in the crown, trunk, roots and any other issues.

To test the internal wood structure a rubber mallet is often used. A resistograph is also used at times to measure wood density. This tool detects internal cracks, cavities, and decay. It’s done by measuring the density of the tree using a drill bit and electronic sensors. Arborist then form recommendation based on the scientific evidence.

Lab Testing:

This may include extracting samples for lab analysis. Scientists can test every part of the tree. They can detect fungal growth in stem tissue to root rot in root hairs. They will also perform a soil analysis around the base of the tree.


The cost and depth of documentation will be different from project to project. Projects vary from observing one tree to a group of trees. A report will include recommendations for the mitigation of risk and status of tree health.

Some tree removal and pruning will require permits from the local municipality. When a permit is needed, some form of documentation is often required. If legal documentation is required, consult a certified consulting arborist. This is different from a regular arborist or even a certified arborist. A certified consulting arborist has received specialized training and testing.

Make sure to follow the recommendations made by your arborist or consulting Arborist. Continue to check your trees for future defects throughout the year. Even if your tree appears safe, it’s always best to verify their health especially if the tree is overhanging valuable property.

We here at GV are more than able to handle your regular tree assessment, including specialized services like root rot treatment. For any lab testing or documentation, we have a consulting arborist who works with us on a routine basis. We can handle an array of assessments and are ready to take on new projects.

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