Guide to Arborist Reports

Arborists provide the technical information needed to make informed decisions about trees. An arborist report should summarize the following:

Factual data such as tree species, trunk size (DBH) and health/structure. Findings may indicate the presence of pests/disease and structural defects (decay, cracks, included bark, etc.) and the distance of any potential failure to targets. For nuisance trees, photos documenting any property damage are helpful.

Arborists may be asked to verify findings with a Level 3 assessment using a resistograph, clinometer, core sample or air spade excavations. 

An arborist's professional assessment based on the findings. Is the tree viable? Does the tree fit nuisance or hazard criteria in KZC 95? What is the potential risk of tree failure? Potential damage to trees on development sites?

These are the reasonable and proper arboricultural practices that apply, which may include tree removal. For development sites, include instructions for working within the tree's Limits of Disturbance and appropriate replacement trees. There are lists of approved replacement trees found on the City of Kirkland's website.


• An ISA Tree Hazard Evaluation form is not a substitute for an Arborist Report, as conclusions and recommendations are not within its format.

• An invoice or bid for tree work is NOT an arborist report.

• TRAQ certification is an excellent basis for tree risk assessment to recommend tree removals in the City of Kirkland.