Panicum pycnocomum Steudel, Syn. Pl. Glumac. 1: 462. 1854; P. viride var. giganteum Franchet & Savatier; P. viride var. majus Gaudin; Setaria gigantea (Franchet & Savatier) Makino; S. pycnocoma (Steudel) Henrard ex Nakai; S. viridis var. major (Gaudin) Petermann (1838), not Gray (1821).

Culms little branched at base, 60–150 cm tall. Leaf blades 15–40 × 1–2.5 cm, glabrous on both surfaces. Panicle sometimes lobed, 7–24 × 1.5–2.5 cm; bristles green, brownish or purplish, 7–12 mm. Spikelets 2.5–3 mm. Fl. and fr. Jun–Oct.

This robust form of Setaria viridis may be of hybrid origin, resulting from crossing with S. italica. Unlike Setaria italica, the spikelets are shed whole.

Roadsides, forest margins, a crop weed, especially in Setaria itali-ca fields; below 2700 m. Gansu, Guizhou, Hebei, Heilongjiang, Hong Kong, Hubei, Hunan, Jilin, Nei Mongol, Shaanxi, Shandong, Sichuan, Xinjiang [Japan, Russia; C and SW Asia, C and S Europe, North America].