Oregon ash in Washington and Oregon

How to identify it

OSU’s plant profile describes a broadleaf deciduous tree 40–80 feet tall with a narrow, dense crown. The key features:

• Opposite leaves, pinnately compound, 15–30 cm long, with 5–7 oval leaflets.
• Single winged seeds (samaras) 3–5 cm long, hanging in dense clusters.
• Its habitat: it survives standing water in winter and, once established, does not need summer water.

OSU calls it “the only ash native to the Pacific Northwest.” Its native range is western Washington and Oregon south into California. Planted ashes of other species are just as much at risk: every ash (Fraxinus) is an EAB host, so the decisions below apply to all of them. If you are unsure, WSU’s EAB page links an identification guide.

Where it grows

ODF’s emerald ash borer fact sheet (September 2024) calls Oregon ash “a key part of riparian forests and wetlands west of the Cascades.” It grows along streams, rivers and wetlands below 2,000 feet, with 80 percent of the species below 1,000 feet, and forms pure stands at the lowest elevations. ODF values it for stabilizing soil, controlling sediment and moderating stream temperatures, and expects ash loss to change water quality and stream temperatures.

For a homeowner, that habitat matters twice. A native ash usually stands on wet ground, which can keep a truck and chipper back from the tree. And trees in streamside and wetland areas often fall under environmental or critical-area rules: Portland, for example, can require a permit for trees smaller than its usual 12-inch threshold in environmental overlay zones.

Emerald ash borer: the threat to every Oregon ash

The first West Coast emerald ash borer was found in Forest Grove on June 30, 2022 (ODA). By 2026, ODF and ODA had confirmed it in Washington, Yamhill, Marion, Clackamas and Multnomah counties, with 2026 finds including Tualatin, Newberg, Silverton, Beaverton, Hillsboro’s Jackson Bottom Wetlands and north and south Salem. Washington’s first detection was in Hazel Dell, Clark County, confirmed by USDA on August 19, 2026.

ODF says EAB “is capable of killing entire stands” and can cause nearly complete mortality of ash within about 10 years of arriving in an area.

The county-by-county detail, signs and the federal and state picture are on emerald ash borer in Oregon and emerald ash borer in Washington.

Signs to check on your ash

ODF says decline usually starts three to four years after a tree is infested, so the first symptoms you can see mean the beetle has been there a while. Check the upper crown first, then the trunk:

• Crown thinning and dieback from the top down (WISC).
• D-shaped exit holes about one-eighth of an inch across, flat on one side (WISC, ODF).
• S-shaped galleries packed with frass under loose or split bark (WSU).
• Heavy woodpecker work and sprouts along the trunk as the tree reacts (WISC, ODF).

Report suspects with photos and a location: in Oregon through the Oregon Invasive Species Online Hotline, in Washington through the WA Invasives app or invasivespecies.wa.gov.

Treat, remove, or wait

Have a certified arborist rate any ash in reach of a structure; see tree risk assessment and dead tree removal.

What to do with the wood

In Oregon, OAR 603-052-1075 bars moving ash logs, green lumber, chips, stumps, roots, branches and firewood of all hardwoods out of the five quarantined counties without an ODA compliance agreement, with civil penalties up to $10,000 (ORS 570.995). ODF’s ash-wood guidance: keep raw ash inside the quarantine, chip it to 1 inch or smaller, and cover loads during the April 1 to September 30 flight season. In Washington there is no EAB quarantine yet, but agencies ask you not to move ash firewood, and Oregon’s rule still applies to wood crossing the Columbia from the Portland side.

Ask the crew where the chips and logs are going before the job starts. Burning rules for the brush are on Oregon yard debris burning rules.

Cost and permits

Modeled estimate, not quotes (method): a 25–50 ft ash models at $900–$1,800 in Oregon and $850–$1,700 in Washington; 50–80 ft at $1,800–$3,600 and $1,700–$3,400, with chipping and haul-away but no stump. If wet ground keeps the truck and chipper away from the tree, the model prices that carry-out at 1.3 times the base. See tree removal cost.

Permit rules for a dying ash are usually the easy case: Portland’s Type A permit covers dead, dying or dangerous trees without public notice (PCC 11.40), and Des Moines excludes ash from its significant-tree count entirely (DMMC 18.195). Elsewhere, check Oregon tree removal permits and Washington tree removal permits. Other species are under trees.