Plants annual or short-lived perennials; often tillering, without rhizomes.
Culms 50-500+ cm tall, 1-5 cm thick, sometimes branching above the base;
nodes glabrous or appressed pubescent; internodes glabrous. Ligules
1-4 mm; blades 5-100 cm long, 5-100 mm wide, sometimes glabrous. Panicles
5-60 cm long, 3-30 cm wide, open or contracted, primary branches compound, terminating
in rames with 2-7 spikelet pairs; disarticulation usually not occurring
or tardy. Sessile spikelets bisexual, 3-9 mm, lanceolate to ovate; calluses
blunt; glumes coriaceous to membranous, glabrous, densely hirsute, or
pubescent, keels usually winged; upper lemmas unawned or with a geniculate,
twisted, 5-30 mm awn; anthers 2-2.8 mm. Pedicels 1-2.6 mm. Pedicellate
spikelets 3-6 mm, usually shorter than the sessile spikelets, staminate
or sterile. Caryopses often exposed at maturity. 2n = 20, 40.
Sorghum bicolor was domesticated in Africa 3000 years ago, reached northwestern
India before 2500 B.C., and became an important crop in China after the Mongolian
conquest. It was introduced to the Western Hemisphere in the early sixteenth
century, and is now an important crop in the United States and Mexico. Numerous
cultivated strains exist, some of which have been formally named. They are all
interfertile with each other and with other wild species of Sorghum.
The treatment presented here is based on de Wet (1978) and is somewhat artificial.
Sorghum bicolor subsp. arundinaceum is the wild progenitor of the cultivated strains, all of which are treated
as S. bicolor subsp. bicolor.
These strains tend to lose their distinguishing characteristics if left to themselves.
They will also hybridize with subsp. arundinaceum, and these hybrids
can backcross to either parent, resulting in plants that may strongly resemble
one parent while having some characteristics of the other. All such hybrids
and backcrosses are treated here as S. bicolor subsp. drummondii.
Coarse, maize-like annual with broad lvs mostly (2-)3-5 cm wide; panicle 1.5-5 dm, its main axis usually ±hairy; pedicellate spikelet mostly shorter than the sessile one, which is spread open by the very turgid grain at maturity; 2n=20. Originally African, now widely cult. in numerous and diverse cultivars. Three interfertile vars. are recognized. Cult. plants with large grains and usually dense, non-disarticulating inflorescences are var. bicolor. Weedy and tall shattercanes and Sudan-grass are var. drummondii (Nees) Mohlenbr. They often occur in sorghum-fields, mature early, and have fragile racemes that readily fragment. The native wild African plants, which form a third var., are ancestors of the cultivars.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.