How to identify Eastern North American Fraxinus species
In our primary target region, there are six, widely recognized native Fraxinus species. Here is a quick key to help distinguish among them during the growing season:
Ash Key illustrations:
1. Young branches 4-angled, winged (l) 2. Lateral leaflets without stalks (l) 3. Leaflets strongly whitened beneath (l)
vs circular (r). vs with stalks (r). vs green or rusty (r).
Other traits and habitat preferences that can help distinguish among these six species are described below. We have included some images of mature fruits (seeds), stems and buds that may be helpful for distinguishing among these species at other times of the year.
F. americanaF. americana typically grows in moist, upland forests, where it often associates with sugar maple, northern red oak, basswood, and yellow birch. Its leaflets are often entire or with very shallow teeth. The bud scars are U-shaped.
Fraxinus americana (white ash).
Shown left to right: seed, twig, leaf (upper side), leaf (under side).
F. carolinianaF. caroliniana typically grows in very wet shrubby thickets along the coastal plain. It is more of a shrub than a tree, with trunks less than 15 cm (6") in diameter. (No images yet available.)
F. nigraF. nigra typically grows in wet woods with spruce and larch, except in the southern part of its range where it can often be found in north-facing forested slopes. Its terminal buds are large and dark brown to black. The bud scars are more-or-less flat topped.
Fraxinus nigra (black ash).
Shown left to right: seed, twig, leaf (upper side), close-up view of leaflets without stalks (under side).
F. pennsylvanicaF. pennsylvanica has the widest habitat range of all native ash, ranging from elm-cottonwood-silver maple floodplain forests to being an old-field invader, even on upland sites. It can also be found with bald cypress and pumpkin ash in inundated swamps. It is extremely variable in twig and leaf pubescence. Its leaflets are usually toothed. Its winter buds are brown and the bud scars flat-topped, half circles.
Fraxinus pennsylvanica (green ash).
Shown left to right: seed, twig, leaf (upper), close-up of toothed leaflet (top, right),
close-up of leaflet gradually narrowing at base and running along upper portion of stalk (lower, right).
F. profundaF. profunda typically grows in flooded open forests with bald cypress and water tupelo. It can be a very large tree, up to 120' tall, with very large leaflets (to 20 cm long) and the largest fruits of all native species. Its leaves are lustrous above and often covered with fine reddish hairs beneath. Young branches are typically covered with velvety hairs. (No images yet available.)
F. quadrangulataF. quadrangulata typically grows on alkaline or calcareous soils (derived from limestone) with a wide range of lime-loving plants, including Kentucky coffeetree, bur oak, hackberry, and red cedar (on particularly dry sites). Its terminal buds are grayish yellow and the bud scars narrowly U-shaped.
Fraxinus quadrangulata (blue ash).
Shown left to right: seed, twig, leaf (upper side), leaf (under side), seeds on branched inflorescence.
F. quadrangulata (blue ash) F. pennsylvanica (green ash) F. americana (white ash) ;F. nigra (black ash).
In addition, Fraxinus excelsior (European Ash) is sometimes cultivated as a landscape tree in the Eastern United States and Canada. It would key to F. nigra above. However, F. nigra has tufts of tan to reddish hairs at the base of each leaflet, but F. excelsior does not.