Culms 20-100 cm; nodes 6-7. Blades 4-12 mm wide. Panicles usually 3-8 cm, producing around 600-800 caryopses. 2n = 18.
Setaria viridis var. viridis is an aggressive adventive weed throughout temperate North America. It is the most common annual representative of Setaria in the Flora region.
Annual herb, tufted 20 cm - 1 m tall
Leaves: alternate, two-ranked. Sheaths sometimes minutely rough, fringed with hairs near the apex. Ligules 1 - 2 mm long, membranous, marginally fringed with hairs. Blades to 20 cm long, 4 - 12 mm wide, lance-shaped, flat, smooth or rough, parallel-veined.
Inflorescence: a terminal arrangement of spikelets (panicle), dense, 3 - 8 cm long, spike-like, with numerous bristles 0.5 - 1 cm long. Axis hairy. Bristles green, rarely purplish, rough.
Fruit: a caryopsis, indehiscent, enclosed within the persistent lemma and palea, ellipsoid to nearly spherical. Between 600 and 800 are produced.
Culm: upright or decumbent, 20 cm - 1 m long, round in cross-section, with six to seven nodes.
Spikelets: nearly stalkless to short-stalked, about 2 mm long, lance-shaped to ellipsoid.
Glumes:: Lower glumes about one-third as long as spikelets, triangular egg-shaped, three-veined, membranous. Upper glumes nearly equal to upper lemmas, elliptical, five- to six-veined.
Lemmas:: Lower lemmas slightly longer than upper lemmas, five-veined, membranous. Upper lemmas pale green, hardened, finely wrinkled, five- to six-veined.
Paleas:: Lower paleas about one-third as long as lower lemmas, transparent. Upper paleas similar to upper lemmas, hardened, wrinkled.
Florets:: Lower florets sterile or male. Upper florets bisexual. Anthers three. Styles two. Stigmas red.
Similar species: No information at this time.
Flowering: June to September
Habitat and ecology: Introduced from Eurasia and now a common weed of waste and cultivated ground.
Occurence in the Chicago region: non-native
Etymology: Setaria comes from the Latin words seta, meaning bristle, and aria, meaning possessing. Viridis means green.
Author: The Morton Arboretum
