Setaria viridis var. viridis

Green Foxtail


CC = *
CW = 5
MOC = 52

© SRTurner

Family - Poaceae/Paniceae

Habit - Annual grass, with soft bases, without rhizomes, relatively easily uprooted, with C4 photosynthesis.

Setaria_viridis_var_viridis_roots.jpg Roots.

© SRTurner

Stems - Flowering stems to 1.0 m, rarely slightly flattened, glabrous.

Leaves - Leaf sheaths rounded on the back to slightly keeled, hairy along the margins and glabrous or more commonly roughened on the surface, the ligule a short membrane with a fringe of hairs, 1-3 mm long. Leaf blades 4-25 cm long, 3-15 mm wide, flat, the upper surface roughened, the undersurface roughened or less commonly glabrous.

Setaria_viridis_var_viridis_leaves.jpg Leaves.

© SRTurner

Setaria_viridis_var_viridis_leaf1.jpg Leaf adaxial.

© SRTurner

Setaria_viridis_var_viridis_leaf2.jpg Leaf abaxial.

© SRTurner

Setaria_viridis_var_viridis_sheaths.jpg Leaf sheaths.

© SRTurner

Setaria_viridis_var_viridis_ligules.jpg Ligules.

© SRTurner

Inflorescences - Dense, narrow panicles with very short branches of few to many spikelets, appearing as cylindrical spikes, 3-10 cm long, usually erect, the main axis with short, soft, upwardly pointing hairs and often also with longer, soft, ascending to spreading hairs, the spikelets subtended by 1-3 green or rarely purple bristles, these 5-12 mm long.

Setaria_viridis_var_viridis_inflorescence.jpg Inflorescence.

© SRTurner

Setaria_viridis_var_viridis_inflorescence2.jpg Inflorescence.

© SRTurner

Spikelets - Spikelets 1.6-2.5 mm long, disarticulating below the glumes. Lower glume 0.5-1.2 mm long. Upper glume 1.6-2.2 mm long. Lowermost floret usually sterile, 1.5-2.5 mm long. Fertile floret with the lemma 1.6-2.1 mm long, with noticeable, fine cross-wrinkles on the surface. Anthers 0.4-0.8 mm long.

Setaria_viridis_var_viridis_spikelets.jpg Spikelets (inflorescence broken in half to expose spikelets).

© SRTurner

Fruits - Caryopses oblong-elliptic in outline.

Flowering - June - October.

Habitat - Forest openings, prairies, streambanks, pond margins, pastures, fields, lawns, gardens, sidewalks, roadsides, railroads, open disturbed areas.

Origin - Probably native to Europe.

Lookalikes - Other species of Setaria, also Alopecurus spp.

Other info. - Green foxtail is a weedy grass common in many disturbed habitats. It occurs across most of Missouri and is found in every state in the continental U.S., though it is less common in the deep South. Important characters for identification are the hairy leaf sheaths and glabrous upper leaf blade surface.

The variety shown on this page, var. viridis, is the more common and smaller of the two varieties generally recognized for the species. The other variety, var. major, is more robust and can closely resemble S. faberi. Note that the treatment in Yatskievych's Flora of Missouri reverses the culm lengths of the two varieties.

Photographs taken along the Katy Trail near Dutzow, Warren County, MO, 9-5-2021 (SRTurner).