Arborists and tree service providers in Seattle

The Tree Service Provider registry

Under SMC 25.11 and SDCI Tip 242C, every tree service provider must register with the Seattle Department of Construction and Inspections (SDCI) before doing commercial tree work in the city. Registration covers more than removals. It applies to:

• Removing any Tier 1, 2, 3 or 4 tree, meaning anything 6 in diameter at standard height (DSH) or larger
• Removing live branches 4 in in diameter or larger
• Pruning or removing live roots 2 in or larger
• Removing 25% or more of a tree’s foliage-bearing area
• Health or hazard assessments of protected trees

To register, a company needs at least one ISA Certified Arborist on staff or on retainer, at least $1,000,000 in commercial general liability insurance naming the City of Seattle as additional insured, a current Seattle business license and a Washington contractor registration under RCW 18.27. Arborists who do hazard tree risk assessments or emergency work must also hold the TRAQ credential.

Work in the street right-of-way is a separate registry run by the Seattle Department of Transportation (SDOT); a company can be on one list, the other, or both. Two notices of violation for separate incidents remove a provider from the SDCI registry for a year, and unregistered providers face penalties double those set in Director’s Rule 10-2023.

Tree tiers and what you can remove

Seattle sorts trees by size at standard height. Outside development, in the zones Tip 242B lists (including Neighborhood Residential, lowrise, midrise and commercial zones), you can remove no more than two Tier 4 trees in any 3-year period without approval. Larger trees need a reason the code accepts, such as hazard, death or an invasive species.

The full removal rules are on the Seattle tree removal page and in the Washington tree removal permits guide.

When you need a tree risk assessment

To remove a tree because it is hazardous, SDCI requires the ISA Basic Tree Risk Assessment form, completed by a certified arborist with a current ISA Tree Risk Assessment Qualification (TRAQ) and submitted by a registered tree service provider. A report from an unregistered company, or from an arborist without TRAQ, does not meet the rule.

During development, Director’s Rule 7-2024 lets a Tier 2 tree come out if a registered provider with TRAQ documents that it is a High Risk hazard or has little or no chance of surviving construction. The assessor weighs crown size, structure, disease, past maintenance, potential damage to existing or future targets, mitigation options and the planned demolition and construction methods.

The application goes through the Seattle Services Portal as a Tree Removal and Vegetation Restoration application, with a site plan, a statement of financial responsibility and, where they apply, the arborist report, risk assessment form and photos. SDCI aims to finish its initial review within two weeks. Dead, invasive and nuisance-tree applications carry no fee; hazard and emergency applications are charged half of SDCI’s hourly rate. See tree risk assessment for what a TRAQ assessment covers.

Posting notice before the work

Registered providers have to follow Seattle’s public notice rules. Notice goes up at least 3 full business days before any reportable work, such as removing a live branch 4 in or larger, and at least 6 full business days before removing any tree 6 in DSH or larger. Posted notices appear on the city’s Tree Public Notice Map, which neighbors can check. Outside an emergency, a crew that offers to start the same day on a regulated tree is skipping a required step.

How to check a provider and an arborist

Start with Seattle’s Tree Service Provider Directory. It lists each provider’s business name, services, registration number and whether it is registered with SDCI, SDOT or both, and you can search by name or service. The list refreshes every evening at 5 p.m., and a new registration or renewal can take up to 48 hours to show.

Then check the people. ISA’s Find an Arborist directory searches by name or certification ID; holders can hide their profile, so ask for the number and search it. ISA certification renews every three years, and TRAQ is a separate qualification earned through a two-day course and a half-day assessment. Confirm the company’s contractor registration with our Washington tree service license lookup. The arborists in Washington page covers other cities, and the arborist guide explains the credentials.

What to do next

Measure the trunk diameter at standard height to find the tier, then decide whether the reason is hazard, death, or something else. For a hazard tree, hire a registered provider whose arborist holds TRAQ, and ask for the completed risk assessment form, not a verbal opinion. SDCI’s tree desk answers questions at (206) 233-5185 or sdci-trees@seattle.gov.

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