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Street Trees

Learn about street trees in unincorporated Washington County.

Street Tree Maintenance

Street trees are generally the responsibility of adjacent property owners.

Our road crews trim trees in the right-of-way if it they block access or sight distance. We may replace trees that were originally planted as part of a County project if they die or damage roads, sidewalks or other infrastructure.

Landscaping is often maintained by adjacent property owners, businesses or homeowners’ associations. Volunteers can maintain landscaping in approved road median locations through Adopt-a-Landscape.

Street trees and limbs may grow into or fall on overhead utility wires. Our road crews are not trained to work around these wires. Call your utility company to report trees on utility wires.

Planting or Removing Street Trees

You can plant a street tree in unincorporated Washington County without a permit, except in Significant Natural Resource areas. Trees in planter strips or landscaping in the right-of-way are often planted during development. The Road Design and Construction Standards include a list of approved street trees.

You need a right-of-way permit if tree planting or removal impacts traffic.

Street trees may need to be removed if their root systems cause damage to sidewalks, roads or other facilities. Adjacent property owners are generally responsible for the repair and replacement of damaged sidewalk panels or other related repairs. To repair damaged sidewalk panels, apply for a sidewalk repair permit.

Neighboring property owners who disagree on tree maintenance may be eligible for free mediation services through Beaverton Center for Mediation and Dialogue (east of 185th Avenue) or Hillsboro Mediation Program (west of 185th Avenue). Washington County does not mediate civil disagreements.

Emerald Ash Borer

The emerald ash borer is an invasive beetle that infests ash trees. The first sighting of the emerald ash borer on west coast happened in Forest Grove in 2022. A tree infested with the emerald ash borer cannot be exterminated and must be removed.

We are dedicated to preventing the spread of this destructive pest.

If you suspect that a street tree has been infested, submit a service request. Our staff are trained to identify signs of the emerald ash borer and suggest appropriate actions. Signs of infestation include bark splitting, D-shaped holes in the bark, thinning or yellowing leaves and basal shoots.

185th Avenue Tree Replanting

We will replace 11 trees on the east side of 185th Avenue between the MAX line and Salix Terrace. The trees are damaging the sidewalk and leaning against the adjacent sound wall. The sound wall was not designed for this stress and is at risk of failing.

An arborist has said the trees must be removed to avoid more damage. We will be replacing the trees with a species suitable for the planter strip. After the trees are removed, we will begin repairing the sidewalk and sound wall.

The work is scheduled for March, 2023. There will be intermittent daytime northbound lane closures on 185th Avenue between the MAX line and Salix Terrace.

Contact(s)