Hoyt Arboretum, Portland, Oregon, USA

Common name: Oregon ash

Family: Oleaceae

Distribution: Western North America: Oregon, Washington and California

Habitat: Riparian areas

IUCN Red list: Near threatened

Hardiness: Zone 6a -10 to -5 F

Life form: Deciduous tree

Usage: Native tree, ornamental, forestry tree

Comments: Oregon ash is the only native ash tree to the Pacific Northwest. It is a common component of low elevation riparian areas, and is currently threatened by fragmentation, development, and the invasive emerald ash borer. Oregon ash is a tall, broadleaf deciduous tree with a narrow, dense crown and a straight trunk. Leaves are opposite, pinnately compound, with 5-7 oval leaflets. Leaflets are sessile or with a short peiolulue, light green above and slightly pubescent below. Fall color is yellow to brown. Trees are dioecious, with separate male and female trees, and precocious flowers (flowers before leaves emerge). Male flowers are clustered and yellowish. Female flowers greenish, developing into dense, drooping clusters of single samara fruits. Oregon ash can grow in full sun to part shade, and can survive standing water in winter months.