Trees to 25 m tall, to 2.5 m d.b.h. Branchlets glabrous or puberulent to densely villous when young. Petiole 7-15 cm, grayish puberulent or glabrous; leaf blade 5-7(-9)-foliolate; petiolules 0.5-2.5(-3) cm, grayish puberulent or glabrous; leaflet blades oblong-lanceolate, oblong, oblong-oblanceolate, or oblong-obovate, 8-25(-30) × 3-8.5(-10.5) cm, abaxially glabrous, grayish tomentose on veins (sometimes only when young), or ± uniformly grayish tomentose or villous, base cuneate to broadly so, rounded, or slightly cordate, margin serrulate or crenulate-serrulate, apex abruptly acuminate; lateral veins in 13-25 pairs. Inflorescence puberulent or glabrous; peduncle 5-10 cm; thyrse cylindric, 15-35 cm, 2.5-12(-14) cm wide at base; branches 2-4(-6) cm, 5-10-flowered; pedicels 2-8 mm. Flowers fragrant. Calyx 3-7 mm, abaxially puberulent or glabrous. Petals 4, white, with yellow spots, subequal, oblong-obovate to oblong-oblanceolate, 8-14 × 3-5 mm, abaxially puberulent. Stamens 6 or 7, 18-30 mm; filament glabrous; anther 1-1.5 mm. Style glabrous or villous except at apex. Capsule yellowish brown, ovoid, globose, obovoid, or pyriform, 3-4.5 cm, densely dotted but smooth; pericarp 1-6 mm thick after drying. Seeds 1 or 2, brown, globose or subglobose, 2-3.5 cm in diam.; hilum white, occupying less than 1/3 to ca. 1/2 of seed. Fl. Apr-Jun, fr. Sep-Oct.

Typical Aesculus chinensis, described from Beijing, is planted, especially in temple grounds and by houses, and is not known with certainty in a wild state. Cultivated plants from S Jiangsu and N Zhejiang were described as A. chekiangensis (reduced to varietal rank under A. chinensis in FRPS), but they are scarcely distinguishable from plants in the Beijing region and in fact have some features that were thought to distinguish A. wilsonii, namely a thinner pericarp and a smaller hilum. Aesculus wilsonii was described from wild plants in Chongqing, W Hubei, and Sichuan, and in its typical form differs from A. chinensis in the above features and in having leaves abaxially pubescent (vs. ± glabrous) with a more rounded base (vs. cuneate). Within the range of A. wilsonii occur numerous intermediates with A. chinensis, as was noted by Hardin (Brittonia 12: 34. 1960), who hypothesized that the latter species might only be a cultivated form of the former. The comment in FRPS about native plants of A. chinensis existing in the Qin Ling mountain range (S Shaanxi) was possibly based on a comment by Rehder (in Sargent, Pl. Wilson 1: 500. 1913), which was questioned by Hardin (loc. cit.), who noted that the specimens he examined from Shaanxi "represent a form of A. wilsonii." Indeed, among the intermediates mentioned above are the same gathering seen by Hardin and another from Mianxian in SW Shaanxi. While extreme forms can easily be assigned to either A. chinensis or A. wilsonii, the existence of so many intermediates makes it impossible to delimit species and difficult even to justify infraspecific taxa. We have therefore decided to recognize one variable species, A. chinensis, but nevertheless to retain a separate status for the wild plants, as var. wilsonii.

● Broad-leaved forests, near streams in tall shady forests, woods, thickets, mountain and hill slopes, ravines, roadsides, also cultivated; below 2000(-2300) m. Native in Chongqing, S Gansu, N Guangdong, Guizhou, SW Henan, W Hubei, Hunan, W Jiangxi, S Shaanxi, Sichuan, and NE Yunnan; cultivated in Hebei, N Henan, S Jiangsu, S Shaanxi, S Shanxi, and N Zhejiang.