Oregon ash is a deciduous tree in the olive family (Oleaceae). It is native to the Pacific coast of North America. The species epithet means “wide leaves [leaflets],” and Oregan ash has wider leaflets than most other ash species. Oregon ash is found growing on deep, poorly drained clays or silty clay loams rich in humus. It will also grow on sandy, rocky, and gravelly soils along waterways or areas with seasonal flooding and prefers a pH of 5 to 7. It will grow in sun to part shade and can be used as a shade tree given the right conditions. It is also used to reclaim wet areas and meadows. This tree grows 65 to 80 feet tall and can be very long-lived, up to 250 years. It grows fast as a young tree but slows down with maturity. The crown is broad and rounded in uncrowded conditions. It is found growing along waterways, bottomlands and other damp to wet sites. It prefers climates with cool and humid summers and winters that are usually mild. Dry conditions will cause stunting of growth, loss of leaves and allow for diseases to take hold. Being dioecious, it needs both male and female trees to produce fruits and seeds. Insects, Diseases, and Other Plant Problems: A variety of fungi cause leaf spot and powdery mildew. A heart rot can cause an extensive defect in older trees. See potential insect and disease problem factsheets to the left. VIDEO created by Ryan Contreras for “Landscape Plant Materials I: Deciduous Hardwoods and Conifers or Landscape Plant Materials II: Spring Flowering Trees and Shrubs” a plant identification course offered by the Department of Horticulture at Oregon State University More information on Fraxinus .
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Clay; High Organic Matter; Loam (Silt); Shallow Rocky
Soil pH
Acid (<6.0); Neutral (6.0-8.0)
Soil drainage
Moist | Occasional Flooding | Occasionally Wet
Growth rate
Rapid
Maintenance
Medium
Canopy layer
2 - Understory
Form & Appearance
Habit / form
Erect; Rounded
Texture
Medium
Foliage
Deciduous
Leaf color
Gold/Yellow; Green
Leaf type
Compound (Pinnately , Bipinnately, Palmately)
Leaf arrangement
Opposite
Leaf shape
Oblong; Ovate
Leaf margin
Entire; Serrate
Leaf feel
Smooth
Leaf size
3-6 inches long, 1-3 inches wide
Hairs present
No
Leaf detail
Odd pinnately compound yellow-green leaves with 5-7 leaflets. Each leaflet is 2-4.75 by 1-3 inches with a rounded base and pointed tip. The margin is serrate to entire. The end leaflet is wider, less serrated and often convex which helps to differentiate it from other ash trees. Fall color is yellow
Fall color
Gold/Yellow
Flower color
Brown/Copper; Gold/Yellow
Flower form
Insignificant
Flower detail
Insignificant male and female inflorescences are borne in clusters on separate trees.
Bloom time
Spring
Fruit color
Brown/Copper
Fruit type
Samara
Fruit size
1-3 inches long, < 1 inch wide
Fruit detail
Female trees produce winged samara with a single seed and single wing in hanging clusters. They are 1- 2 inches long
Bark color
Dark Brown; Dark Gray
Bark detail
The bark is dark gray-brown and matures to a woven pattern of deep fissures and ridges.
Stem color
Brown/Copper
Stem detail
Twigs are opposite and stout with opposing buds and wooly hairs
Wildlife & Ecology
Native status
Native
Origin
Southwestern Canada to California
Distribution
Oregan, CA, WA
Wildlife value
Seeds are eaten by songbirds, squirrels, and waterfowl. Deer and elk will graze its foliage and sprouts. It also provides food to some butterfly larvae.