Lake Oswego homeowners face new tree-removal rules as of Thursday, Oct. 1. The updated code sets a 45% retention standard for certain residential projects and creates a streamlined permit for ash trees threatened by the emerald ash borer.

The City Council approved two ordinances updating the tree code at its July 21 meeting, as first reported by the Lake Oswego Review. The changes respond to a state law requiring local governments to apply clear and objective standards for tree removal tied to housing development.

The biggest shift is a new "Clear & Objective Track" for Type II tree removal applications linked to new homes and residential lot creation. Builders must retain at least 45% of trees with a diameter greater than 15 inches or pay a fee. That non-discretionary track covers less than 17% of all tree permits in the city. A separate discretionary track with subjective standards remains available.

Faster permits, new mitigation rules

The updated code cuts the review timeline for Type II applications from three weeks to two. Community Development Director Jessica Numanoglu said at the July 21 council meeting that the amendments improve regulatory clarity and efficiency.

Mitigation is now required for Type I permits, except for fruit trees. The city's Native Tree Mitigation List and Master Plant List have been updated to remove ash trees and add drought-tolerant, wildfire-resistant species as acceptable substitutes.

Ash tree removal gets easier

Homeowners with ash trees can now remove them through a simple over-the-counter permit, according to the city's Oct. 1 notice. The change is part of Lake Oswego's broader response to the emerald ash borer (EAB), a wood-boring beetle first discovered in Oregon in Forest Grove in 2022. EAB has since been found in five Oregon counties, including Clackamas.

"With EAB being permanently established in Oregon, it'll inevitably spread to Lake Oswego and it cannot be eradicated, but a proactive plan can minimize the ecological, economic and safety impacts to our community," urban forester Courtney Wilson said at the council's Aug. 4 meeting. Wilson spoke as members approved an EAB readiness plan, as reported by the Lake Oswego Review.

A 2025 city inventory found 528 potentially hazardous trees among 2,711 surveyed near park boundaries and trails. Staff estimated future EAB remediation could cost between $300,000 and $800,000, funding the city plans to include in its 2027–29 biennium budget.

Two free workshops ahead

The city is hosting two free hybrid workshops to walk residents, arborists and contractors through the changes:

  • Thursday, Oct. 29, 5–6:30 p.m.: "Tree Removal Permits: Permit Types & Recent Code Amendments," led by associate planner Daphne Cissell and contract arborist Morgan Holen. The session covers permit types, criteria for dead, dying and EAB-susceptible trees, and how to complete the updated application checklist.
  • Thursday, Nov. 12, 5–6:30 p.m.: "Clear & Objective Track Type II for Residential Development."

Both sessions are available in person or via Zoom. In-person capacity is limited to 40. Pre-registration is required. Residents can find workshop details and registration links on the city's tree workshop page.

The city will no longer accept old versions of tree removal applications. Updated forms are available on the city's planning website.