green ash ( Fraxinus pennsylvanica)
Green ash on Wellshire Golf Course in Denver.
Species info:
Leaves: Opposite, pinnately compound, up to 12 inches long with 5–9 leaflets (most commonly 5–7). Each leaflet is 2–5 inches long, lanceolate to ovate, with finely serrate or nearly entire margins. Shiny green above and dull green below.
Leaflets: 5–9 per compound leaf.
Leaf Surface: Smooth, glossy upper surface; lighter and slightly fuzzy below.
Bark: Distinctive interlacing furrows forming elongated diamond-shaped ridges on older trees. Young bark is smooth and somewhat orange in color.
Twigs: Stout, rounded, velvety or smooth; leaf scars are half-circular with a closed C-shaped vascular bundle scar (unlike white ash, which has a notched leaf scar).
Flowers: Inconspicuous; appear before leaves in spring. Dioecious (male and female flowers on separate trees).
Fruit: Clusters of single-winged samaras, 1–2½ inches long and about ¼ inch wide, paddle-shaped. Many cultivated varieties are seedless (male).
Botanical: Fraxinus pennsylvanica
Family: Oleaceae
Mature Height: 60 feet
Canopy Spread: 25–40 feet
Foliage Type: Deciduous
Tree Shape: Pyramidal when young, developing into a broadly oval or irregular crown
Growth Rate: Fast (1½–2 feet per year under favorable conditions)
Fall Color: Yellow
Water Use: Moderate; adaptable to varying moisture levels
Hardiness: Zones 3–9
Soil Preference: Adapts well to a wide range of soil types, including those with high pH; prefers well-drained, moist soils
Wildlife Value: Provides cover and nesting habitat for birds; seeds eaten by small mammals and birds
Pests/Pathogens: Emerald Ash Borer (EAB) is a major threat to ash species nationwide; lilac ash borer; ash bark beetle; Cankers and root collar rot occur in Colorado, especially in stressed trees.
Planting Recommendations: Not recommended due to emerald ash borer.
Information Sources:
Front Range Tree Recommendation List
Michael Kuhns, Trees of Utah and the Intermountain West (Utah State University Press, 1998)
Michael Dirr, Manual of Woody Landscape Plants (University of Georgia, 1990)
Whitney Cranshaw, Garden Insects of North America (Princeton University Press, 2004)
National Audubon Society, Field Guide to Trees, Eastern.
