Oregon Ash is found to the west of the Cascade Mountain Range from southwestern British Columbia, south through western Washington, Oregon and into the Sierra Nevada range in California. In general, it will grow from sea level up to 3,000 feet in elevation.
There are approximately 65 species of ash that grow mostly in temperate regions of the northern hemisphere, worldwide. Sixteen of these species occur in North America. Oregon Ash is the only ash native to the Pacific Northwest.
Oregon Ash is a medium sized (up to 25 meters) deciduous tree that is a member of the olive family (Oleaceae), living up to 250 years. This species prefers poor-draining, moist or wet soils found along streams, wetlands or low valleys as these trees are able to withstand frequent flooding.
A more familiar ash tree is the non-native and showier Mountain Ash or Rowan Tree with its bright red berries. The Mountain Ash is a member of the rose family and grows best in moist, acidic, well-drained soils in full sun or part shade. These ornamental trees are a favorite for landscapers for their white blossoms and showy bright berries. Our Pacific Northwest Ash is a bit subdued in comparison but hardy and a favorite of local butterflies.
Oregon Ash thrives in mild, humid climates that have relatively cool, humid summers and wet, mild winter temperatures. These trees will tolerate summer drought but may drop leaves when conditions become too hot and dry.
The spring blooming flowers appear before leaf-out and are inconspicuous with male and female parts growing on separate flowers. Seeds are single winged, like half a maple seed forming in large drooping clusters. Young trees are fast growing while growth slows as the tree matures. Seedlings are able to propagate in shady areas.
Given the right conditions, and if your space allows, these trees are easy to grow and can provide valuable habitat for wildlife. Birds and small animals eat the seeds and deer browse on young plants. Butterflies, such as the Western Tiger Swallowtail, will use the plant as a host for its larvae to feed upon the leaves.
For more information about native plants, visit Washington Native Plant Society.