Flower:

Drooping clusters at branch tips appearing about the same time as when leaves emerge. Male and female flowers are long stalked, greenish yellow, borne on separate branches of the same tree, sometimes on separate trees or on the same branch. Occasionally flowers are perfect (contain both male and female parts). The flower stalks are hairy, the calyx five lobed and without petals, the male stamens extended just beyond the calyx, the females with two extended stigmas, sometimes several times as long as the calyx.

Leaves and bark:

Leaves are simple and opposite, the blade up to 6½ inches long and 7¼ inches wide with 3 to 5 palmate lobes, the two basal lobes much reduced with only rounded tips or sometimes lacking altogether. The leaf stalk is about the same length as the blade, smooth to short-hairy, and typically has conspicuous, hairy stipules (leafy appendages) at the base.

Upper surface is dark green and hairless, the lower surface paler with fine, erect hairs, more densely along major veins which gives it a soft, velvety feel. Edges are often drooping and typically have 1 to 6 points on each side.

One year old twigs are smooth and brown to grayish, older branches and trunk are dark gray with short, corky ridges. The trunk can grow to 48 inches in diameter at breast height (dbh).

Fruit:

Fruit is a pair of winged seeds (samara), that can be up to 1½ inches long but more typically around an inch. Fruit matures from September into October. The wings form between a 45 and 90 degree angle.

Notes:

Black Maple is a large forest tree found only in Minnesota's southeast. It is somewhat cryptic in being very similar to the more widespread Sugar Maple (Acer saccharum) that frequently shares its habitat, and the two do hybridize. There is some discussion whether they should both be treated as varieties of A. saccharum, but the current status in Minnesota is they are distinct species. Black Maple is more tolerant to some sedimentation and can grow in floodplains that experience minimal flooding, where Sugar Maple will be found only in upland mesic forest. Leaf characteristics for the two are rather variable and there is much overlap so are not always reliable, but Black maple leaves typically have 6 or fewer points per side, where Sugar Maple usually has 5 to 11. The leaf margins of Black are consistently drooping, especially when young, but Sugar may display this as well. Black, however, has stipules at the base of the leaf stalk and, while not present or of great size on every leaf, invariably these can be located throughout the branches. Sugar does not have these stipules. Also, Black is fairly consistently hairy across the lower surface of the leaf giving the leaf a soft velvety texture. Sugar is usually only hairy along the main veins or just in the vein axils, but when present on the surface, the hairs are typically sparse and appressed giving the leaf a soft silky texture.