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.

Similar species: Sorghum halepense is a perennial that bears rhizomes and has caryopses that are not exposed when mature. Sorghum bicolor ssp. bicolor differs from other subspecies because it has exposed caryopses and inflorescence branches that remain intact at maturity.

Flowering: mid September to mid October

Habitat and ecology: Introduced from Eurasia, this species is frequent along railroads and grain elevators and local near bird feeders or other areas with spilled seed.

Occurence in the Chicago region: non-native

Notes: This species was first cultivated in Africa 5,000 years ago and has become an important crop around the world.

Etymology: Sorghum comes from the plant's Italian name, sorgo. Bicolor means "of two colors."

Author: The Morton Arboretum