Seattle, WA Landscaping Rules: Tree Removal & Heritage Trees (2026)

11, Tier 1 through Tier 4 trees, plus trees on undeveloped lots, once it is proposed for removal as hazardous. A registered tree service provider whose staff or retained arborist holds a current ISA Tree Risk Assessment Qualification must first complete a written risk assessment rating the tree Extreme Risk (imminent failure, high likelihood of hitting a target, severe consequences), High Risk, Moderate Risk, or Low Risk. If no potential target, a permanent structure or an area of moderate-to-high use, exists, the applicant may be limited to normal pruning rather than removal.

Where a tree rates High Risk, the SDCI Director may authorize hazard pruning instead of removal; where pruning or moving the target is not feasible, the Director may designate the tree hazardous and allow full removal. Dead trees are exempt from the risk-assessment and replacement steps. 030: a registered provider with the same ISA credential must first confirm extreme imminent-failure risk, the Director must be notified by email or through SDCI's website before work begins, and a hazardous tree removal application documenting the ISA risk-assessment form and photographs must be filed with SDCI within ten calendar days of the emergency action. 120. 090, sized and species-selected by the Director, unless the removed tree was already dead.