A tree usually under 30 ft high, but sometimes up to 70 ft, with a trunk over 6 ft in girth; bark of the trunk rough, and much fissured. Leaves usually composed of five leaflets, which are 3 to 6 in. long, about one-third as wide; obovate or oval, with a long, tapering point, sharply toothed; downy when young, but becoming glabrous with age, except along the midrib and chief veins. Flowers about 1 in. long, greenish yellow, in erect panicles 4 to 7 in. long, 2 to 3 in. wide; petals four; stamens 1⁄3 in. longer than the petals. Fruit 1 to 2 in. long, broadly obovoid, distinguished from other American buckeyes by prickles resembling those of common horse-chestnut, but much less prominent.
Native of the S.E. and Central United States. This tree is of handsome shape and foliage, but is the least attractive of the genus in its flowers. Often confused with A. flava, it is readily distinguished by its rougher bark, the less downy leaves, the longer outstanding stamens, and the prickly surfaced fruit. It flowers at the end of May and in early June. It grows well at Kew, where the largest specimen is now 56 × 63⁄4 ft (1967).
var. leucodermis Sarg. – Native of southern Missouri and Arkansas; best distinguished by its smooth, near-white bark, which only becomes scaly on old trees. Leaves glabrous.
var. monticola Sarg. – Differs in having six or seven leaflets and a more rounded fruit; found wild in Oklahoma.
f. pallida (Willd.) Schelle A. pallida Willd. – Leaflets pubescent at maturity. Introduced to Britain in 1812. It is found wild in the Middle West.
var. sargentii Rehd. var. arguta Robins, in part; var. buckleyi Sarg. – A form with six or seven leaflets, also distinct in their longer, drawn out points and their doubly toothed margins. It does not reach so far eastward as the typical A. glabra and is found in Ohio and westward to Oklahoma. This variety has been confused by botanists with A. arguta.
From the Supplement (Vol. V)
specimens : Kew, 60 × 71⁄2 ft and, var. leucodermis, pl. 1912, 52 × 4 ft (1980); Clare College, Cambridge, 40 × 43⁄4 ft (1981); Corsham Court, Wilts., 52 × 41⁄4 ft (1981); Edinburgh Botanic Garden, 40 × 41⁄2 ft (1981).
† A. × mississippiensis Sarg. – A hybrid between A. glabra and A. pavia, which could be confused with A. × hybrida. The most reliable difference would appear to be in the fruits. These are warted, a character no doubt deriving from the prickly fruits of A. glabra and the smooth ones of A. pavia; in A. × hybrida they are smooth, as in both its parents. Another difference is said to be that the stamens are usually longer than the petals (shorter in A. × hybrida). A possible earlier name for this cross is A. × bushii Schneid.