A very easily recognized genus, with its opposite, palmately compound leaves and distinctive large fruit. The latter is a capsule, the outside ± prickly (in our common species) and only 1 or occasionally 2 (very rarely more) large seeds developing within. The seed has an unusually broad pale scar (hilum) representing the area of attachment; the rest of it is a shiny rich reddish brown when ripe. 

Other species of Aesulus are cultivated for ornament, especially A. flava Sol., A. pavia L., and A. sylvatica W. Bartram, in addition to hybrids. Any of these might stray from cultivation and A. pavia, with red flowers, is known as an escape in southern Ontario.

1. Terminal buds brown, either finly striate or glutinous; fruit prickly; flowers yellow or white, in both cases with a darker yellow to red center, stamens not or short-exserted beyond the petals; single-trunked trees.

 2. Leaflets 5, tapered ± gradually to tip; winter buds striate, not glutinous; hilum not over 1/2 as broad as the diameter of the seed; flowers yellow-green.

A. glabra

 2. Leaflets mostly 7, abruptly acuminate to a short tip; winter buds very glutinous-sticky; hilum about two-thirds or more as broad as the seed; flowers white..

A. hippocastanum

1. Terminal buds whitened and waxy, dotted with abundant small round, brownish glands; fruit smooth; flowers pure white, stamens long-exserted, more than twice as long as the petals; suckering colonial shrubs.

A. parviflora