Note: Due to the recent arrival of emerald ash borer in Oregon, ash trees in our region are at high risk of mortality over the next several decades. See OSU Extension Service’s emerald ash borer resources page for more information about how you can slow the spread and protect your ash trees.
* * *
Oregon ash is native to western North America on the west side of the Cascade Range from southwestern British Columbia south through western Washington and western Oregon to central California.
It can grow to 80 ft in height, with a trunk diameter of 3ft. The leaves are pinnate, 3.5-10″ long, with 5-9 ovate leaflets. The fruit is a samara, 3-5 cm long including the wing. The leaves turn a striking yellow in the fall.
Oregon ash prefers damp, loose soils, and grows from sea level to 900 meters. It is a dominant tree in local forested wetlands, paired with an understory of spiraea and slough sedge.
Oregon ash is an ideal deciduous tree to plant along streams, seeps, and wet areas. It forms an attractive shape, tolerates saturated soils, and shades waterways.
