Description from Flora of China
Holcus bicolor Linnaeus, Mant. Pl. 2: 301. 1771; Andropogon bicolor (Linnaeus) Roxburgh; A. sorghum (Linnaeus) Brotero; A. sorghum var. technicus Körnicke; Holcus cernuus Arduino; H. dochna Forsskål; H. sorghum Linnaeus; Sorghum cernuum (Arduino) Host; S. dochna (Forsskål) Snowden; S. nervosum Besser ex Schultes; S. technicum (Körnicke) Roshevitz; S. vulgare Persoon, nom. illeg. superfl.
Annual. Culms erect, robust, 3–5 m tall, 2–5 cm in diam.; nodes glabrous or pubescent. Leaf sheaths glabrous or slightly farinose; leaf blades linear or linear-lanceolate, 40–70 × 3–8 cm, glabrous; ligule subrounded, ciliate. Panicle very variable, lax or dense, cylindrical or pyramidal to obovate in outline, up to 60 cm, main axis elongate to very short; primary branches ascending or spreading, lower branches sometimes almost as long as panicle, stiff or pendulous; racemes tough at maturity, composed of 2–6 spikelet pairs. Sessile spikelet variable, broadly obovate to subglobose, 3.5–5.5 mm; callus hispid; lower glume leathery to papery, glabrous to pilose, pale creamy-green to dark brown or blackish at maturity, upper lemma usually awned; awn 0.4–1.5 cm. Pedicelled spikelet male or barren, linear-lanceolate, persistent or deciduous. Caryopsis large, often exposed between the gaping glumes. Fl. and fr. Jun–Sep. 2n = 20.
Sorghum bicolor is the important, tropical cereal sorghum. Originating in Africa, its cultivation for both grain and fodder spread throughout the tropics and subtropics of the Old World. It was introduced with the slave trade to America, including warm parts of the United States. It is now cultivated throughout most of China.
There is a multiplicity of forms of cultivated sorghum, derived by human selection and all fully interfertile. Some forms have sweet culms. Many species names have been proposed in the past in an attempt to categorize this variation, but they represent no more than intergrading cultivars within the common species pool.
The name Holcus saccharatus Linnaeus (Sorghum saccharatum (Linnaeus) Moench) has been identified as this species, but its application is uncertain (see Davidse & Turland in Taxon 50: 577–580. 2001) and the name has been formally rejected.
The principal races grown in China are as follows.
高粱 gao liang
Panicle loose with long branches, to 40 cm. Sessile spikelets broadly obovate; glumes leathery, glossy. Grain relatively small, enclosed within the glumes or only the top protruding.
Cultivated for grain; a primitive type.
弯头高粱 wan tou gao liang
Panicle elliptic or ovate-elliptic, dense, 8–20 cm, curved or erect. Sessile spikelets broadly ovate, whitish; glumes thin, papery, transversely wrinkled, densely white-villous to glabrescent. Grain pale, subrotund to orbicular, usually much flattened, protruding beyond the glumes.
Cultivated in Xinjiang for grain and forage.
甜高粱 tian gao liang
Culms with sweet juice. Panicle elongate, to 50 cm; branches racemose or corymbose, the lower ones half as long as panicle or more. Sessile spikelets broadly elliptic to obovate; glumes crustaceous, striately veined above middle. Grain elliptic or elliptic-oblong, enclosed by the glumes or only slightly protruding.
Cultivated for grain and forage throughout most of China, including forms used for making brooms.
多脉高粱 duo mai gao liang
Panicle elongate, dense, elliptic in outline, to 40 cm. Sessile spikelets elliptic to broadly elliptic; glumes papery, prominently veined ± throughout. Grain broadly elliptic, protruding beyond the glumes.
Cultivated for grain, mainly in N China.
Cultivated in China [native to Africa; widely cultivated in the tropics].