Seattle's tree service registry: what homeowners need to know

Which jobs need a registered provider

The registry applies to commercial tree work on private property, which the City defines to include:

• removing live branches 4 inches or more in diameter;
• cutting live roots 2 inches or more;
• removing a quarter or more of a tree's foliage;
• removing any tree 6 inches or more in diameter at standard height;
• paid assessments of a tree's health or hazard risk.

Source: City of Seattle registry requirements. If your job falls under any of these, ask the company for its City registration number.

What a company needs to register

• A current City of Seattle business license.
• A Washington L&I general contractor number.
• Commercial general liability coverage of at least $1,000,000 per occurrence, naming the City as additional insured.
• At least one ISA Certified Arborist on staff or retainer. Hazard risk assessments and emergency actions need an arborist with the TRAQ qualification.

Registered providers renew every year and must show their City registration number on their work vehicles. (City of Seattle)

Tree sizes the City tracks

Seattle sorts trees into tiers. Tier 2 covers trees 24 inches or more in diameter, plus groves and some listed species. Tier 3 runs 12 to 24 inches, and Tier 4 runs 6 to 12 inches. Ask the company which tier your tree falls in and what notice or permit the City needs before work starts. The City's tree regulations page has the current rules.

How to check a company

1. Find the company in the City's Tree Service Provider Directory, linked from the registry page.
2. Confirm the L&I registration on Verify.
3. Look up the arborist by name in ISA's Find an Arborist directory.

Outside Seattle, the registry does not apply, but the L&I check does. See how to hire a tree service or browse tree services in Seattle.