Flower:

Flowers are borne on feathery, yellowish panicles, 1 to 2 inches long, from leaf axils of one-year-old branchlets. Male and female flowers occur on separate trees, both lacking petals and calyx, the male typically with just two, often red or purplish stamens, the female with only a single, reddish style. Flowers emerge before the leaves in spring.

Leaves and stems:

Leaves are opposite and pinnately compound, 9 to 16 inches long with 7 to 13 oval to lance-elliptic leaflets. Leaflets are 3 to 5½ inches long and 1 to 2¼ inches wide, stalkless, with finely toothed edges and a long or abrupt, short taper to a pointed tip. The upper surface is dark green and smooth, the lower surface paler with short, matted brown hairs along the lower part of the midvein. The leaflets in the middle of the leaf are somewhat larger than those on the ends.

Branchlets are smooth, greenish brown to gray colored with light brown lenticels (pores) the first year. Branches turn brownish gray with corky ridges; older bark has thin, flat scales.

Fruit:

Fruit is a single, winged seed (samara), narrowly oblong-elliptic, 1 to 1¾ inches long and ¼ to ½ inch wide, in open dangling clusters that can persist on the tree all winter. The wing extends all the way to the base with barely a bulge from the very flat seed inside.

Notes:

Black Ash is Minnesota's most common ash species with over 600,000,000 trees, mostly in the northern half of the state. In moist upland forest it is a tall straight tree getting over 100 feet tall and up to 30 inches in diameter at breast height. But it is quite tolerant of wet, swampy sites though performs poorly, often creating large stands of scrappy, narrow-crowned trees with a lot of crown dieback. One of our last trees to leaf out in spring, it wears a brief yellow fall color before shedding its leaves in early autumn. It can be differentiated from our other two native ashes by its stalkless leaflets, scaly bark, and samaras that are very flat and winged all the way to the base. In winter the dormant buds are dark brown to nearly black, the terminal looking much like a deerhoof, and the lateral bud scars oval to slightly crescent shaped, similar to those of Green Ash (Fraxinus pennsylvanica), except for a short internode (gap) between the terminal bud and the first lateral buds below it (see photo below). The loss of this huge population of trees to emerald ash borer will likely have a profound effect upon the ecosystems it inhabits, especially on water quality in the watersheds it now helps protect.