Oregon Ash

Oregon ash (Fraxinus latifolia, Oleaceae) is the only ash species native to western North America, ranging from western portions of Washington and Oregon south through the Coast Range and Sierra Nevada to central California. It reaches 40 to 80 feet (occasionally exceeding 80 feet) with a broad crown nearly as wide as it is tall in open conditions. Opposite, pinnate compound leaves (15 to 30 centimeters) carry 5 to 7 elliptical leaflets. Dioecious flowers (3 millimeters, male yellowish, female greenish) appear without petals before leaves in April to May. Single samaras (3 to 5 centimeters) hang in dense clusters.

Oregon ash grows in sun to part shade on adaptable soils (pH 4.8 to 7.0) with moderate water needs and high tolerance of wet, anaerobic conditions, hardy in Zones 6a to 8b. It is shade-intolerant and thrives after floods and disturbance, resprouting vigorously from stumps. Growth is moderate, reaching about 35 feet at 20 years. Disease (8 documented) and pest (9 documented) associations match the genus. The emerald ash borer is the dominant threat. Indigenous peoples used the wood for canoe paddles and digging sticks. No cultivars are in the trade.