薯蓣 shu yu

Dioscorea batatas Decaisne; D. decaisneana Carrière; D. doryphora Hance; D. potaninii Prain & Burkill; D. rosthornii Diels; D. swinhoei Rolfe.

Tubers vertical, cylindric, to 1 m; transverse section white. Stem twining to right, often purplish red, glabrous. Bulblets present in leaf axils. Leaves alternate basally on stem, mostly opposite distally on stem, rarely in whorls of 3, simple; petiole 2--3 cm; leaf blade often drying grayish or greenish, ovate-triangular to sagittate, usually 3-lobed, relatively wide and ± entire on juvenile leaves, 3--7(--16) × 2--7(--14) cm, papery to thinly leathery, glabrous, basal veins 5 plus 1 or 2 pairs restricted to basal lobes, base shallowly (rarely to deeply) cordate to subtruncate, apex acuminate; lateral lobes auriculate, subrectangular to oblong, rounded. Male spikes 2--8 together, erect, 2--8 cm, rarely paniculate; rachis obviously zigzagged. Male flowers: sessile; bracts triangular-ovate, ca. 1 mm; perianth yellow with purplish brown dots, outer lobes broadly ovate, 1.3--2 × 0.8--1.2 mm, concave, inner ones ovate, smaller than outer; stamens 6. Female spikes solitary or 2 or 3 together. Capsule not reflexed, oblate or globose, (1.2--)1.7--2 cm, pruinose; wings 0.7--1.5 cm wide. Seeds inserted near middle of capsule, winged all round. Fl. Jun--Sep, fr. Jul--Nov.

Forests, scrub forests, herb communities, mountain slopes, along rivers, roadsides, also commonly cultivated; 100--2500 m. Anhui (S of Huai He), Fujian, E Gansu, N Guangdong, Guangxi, Guizhou, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, S Shaanxi, Shandong, Sichuan, Taiwan, N Yunnan, Zhejiang [Japan, Korea].

An important food crop.