Aesculus glabra
Ohio Buckeye (Aesculus glabra)

Distribution Map to Right
Counties in Blue contain tree

Shape and Distribution
Ohio buckeye is a medium-sized tree, reaching heights of 40 - 60 feet, with a relatively short trunk about 15 inches in diameter. The crown is broadly rounded and the branches hang downward. 

In the open, Ohio buckeye has a short, knotty trunk and branchy appearance. When grown in a closed forest, the trunk is generally straighter and the tree self-prunes and is not as branchy. Ohio buckeye grows in moist, rich soils in mesic forests throughout Illinois. It grows with sugar maple, hackberry, Kentucky coffee tree, American elm, and red mulberry. It also occurs on moist, but not flooded, bottomland soils along streams with black walnut and sycamore.

Interesting Facts
Ohio buckeye is also referred to as stinking or fetid buckeye because the leaves and twigs give off an unpleasant odor (skunk-like) when crushed. The buckeye portion of the name derives from the fruits, which are mahogany brown with a large gray spot, resembling a buck's eye. The bark and seeds contain a narcotic chemical that is poisonous to livestock. As a result, many farmers have removed the tree from pastures.

Identifying Features

The bark is pale gray with corky warts, deeply furrowed, and stinks when cut into. 
The twigs are stout, rounded, gray or brown, and curve upward with maturity. They are hairy when young, becoming smooth with age. They, too, emit a fetid odor when crushed. 
The buds are about 2/3 inch long, ovoid but pointed at the tips, and reddish brown. The leaves are 8 - 14 inches long. They are opposite, palmately compound (shaped like a hand with the palm facing upward), with 5-7 obovate (oval with a pointy end) to lance-shaped, leaflets with long, pointed tips. 
The leaf stalk is up to 6 inches long, and the leaves are dark green and smooth on the surface and paler below. The leaves emit a horrid, skunk-like odor when crushed. In the fall, they turn yellow to brown.
Ohio buckeye is "polygamo-monoecious" - it bears both bisexual (perfect stamens and pistils present in the same flower) and male (staminate) flowers. The numerous flowers appear in erect clusters, sometimes almost a foot long (but more often 5 - 7 inches), in April and May. They are creamy yellowish green and very showy. 
The fruits are prickly and nearly spherical, up to 1 1/2 inches in diameter, and enclose one, two, or three seeds. The seeds are smooth, mahogany colored with a large gray spot.
Ohio buckeye wood is soft, close grained, and weak. It is used for furniture and pulpwood. Whereas the seed is considered poisonous to livestock (cattle), squirrels reportedly eat the seed in Ohio, and fox squirrels in Illinois are reported to eat the pith of the twigs. Ohio buckeye is occasionally planted as an ornamental.