Fraxinus pennsylvanica Marsh., green ash, is a deciduous, medium-sized tree with an open, irregular crown reaching about 50 feet in height. Native to eastern North America and is fairly common west to Wyoming and Colorado along plains watercourses at elevations below 6,000 feet. The tree is fast growing on moist bottomlands, and is extremely hardy to climatic extremes once established.

Fruits are straw-colored, one-seeded, winged (samaras), 1 to 2 1/2 inches long, borne in dense branching clusters; flowers are inconspicuous, without petals, borne in dense clusters (panicles) near the ends of the twigs, male and female flowers on separate trees; leaves are opposite, pinnately compound, 4 to 6 inches long, 7 to 9 leaflets, narrowly elliptical, long-pointed, entire, bright green above, paler below; stem straight, bark thin with network of interlacing ridges, brown to dark gray, twigs smooth; roots are shallow, wide-spreading.