Green Bristlegrass

Setaria viridis, Green Bristle Grass, is extremely close to the cultivated Setaria italica. differing mainly in the manner in which the spikelet breaks up. In Setaria viridis, as in other species of Setaria, the spikelet falls entire from the pedicel, but in Setaria italica the glumes and lower lemma persist while only the upper floret is shed.

Annuals; clum glabrous, geniculate, 40-80 cm tall. Blade broadly linear, 5-20 cm long, 2-18 mm wide; sheath ciliate on margins; ligule a ring of hairs, ca. 1.5 mm long. Panicle contracted, spike-like, cylindrical, 3-6 cm long; axils pubescent; sterile branches forming bristles subtending spikelet. Spikelets 2-2.5 mm long, 0.8-1 mm wide; elliptic, usually obtuse; lower glume 3-veined, ovate, ca. 1/3 as long as spikelet; upper glume 5-veined, equaling spikelet or shorter; lower lemma 5-veined, enclosing a small, narrow, lower palea; upper lemma oblong, obtuse, obscurely rugose, finely punctate. Anthers ca.0.7 mm long.

Annual. Culms tufted, erect or geniculate, up to 70(–150) cm tall, 3–7 mm in diam. Leaf sheaths glabrous to papillose-pilose, margins densely ciliate; leaf blades linear to linear-lanceolate, flat, glabrous or papillose-pilose on both surfaces, base subrounded or subtruncate, margins scabrous, apex acuminate; ligule 1–2 mm. Panicle dense, usually cylindrical, usually tapering upward, 1–24 cm, erect or slightly nodding, branchlets bearing several spikelets each subtended by 3–7(–25) bristles; axis pilose or pubescent; bristles green, brown or purple, 4–12 mm. Spikelets elliptic-oblong, 2–2.5(–3) mm, obtuse; lower glume 1/4–1/3 as long as spikelet, obtuse or rarely acute; upper glume elliptic, as long as spikelet, lower lemma equal to spikelet; lower palea about 1/3 as long as lemma; upper lemma pale green, oblong, finely punctate-rugose, obtuse. Fl. and fr. May–Oct. 2n = 18.

Loosely tufted annual; culms 10-50 cm high, erect or geniculately ascending. Leaf-blades broadly linear to narrowly lanceolate, 5-20 cm long, 4-12(18) mm wide, rounded at the base, flaccid, smooth or scaberulous; sheaths glabrous to pubescent, sometimes with tubercle-based hairs. Panicle spiciform, linear or sometimes ± lobed below, 2-12 cm long, the rhachis puberulous to hispidulous; bristles 3-12 mm long, antrorsely scabrid. Spikelets ellipsoid, 2-2.5(3) mm long; lower glume a quarter to a third the length of the spikelet; upper glume as long as the spikelet; lower floret barren, its plea about half as long as the lemma; upper lemma finely rugose.

Cooler parts of Old World, introduced in New World.

Widely distributed in the Old World. Taiwan, in sandy seahsores.

Distribution: Pakistan (Baluchistan, Punjab, N.W.F.P., Gilgit & Kashmir); in the cooler regions of the Old World; introduced to the New World where it has escaped and is considered a weed.

2300-3800 m

Fl & Fr. Per.: June-September.

Hill slopes, roadsides, grassy waste places. Anhui, Fujian, Gansu, Guangdong, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [temperate and subtropical regions of the Old World; introduced elsewhere].

Panicum viride L., Syst. Nat. ed. 10. 2: 870. 1759. Panicum pachystachys Franch & Sav., Enum. Pl. Jap. 2: 161. 1876. Setaria viridis (L.) P. Beauv. var. pachystachys (Franch. & Sav.) Makino & Nemoto, Fl. Jap. 1499. 1925; Hsu, Fl. Taiwan 5: 608. 1978.

Annuals, Terrestrial, not aquatic, Stems trailing, spreading or prostrate, Stems nodes swollen or brittle, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes solid or spongy, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems with inflorescence 1-2 m tall, Stems with inflorescence 2-6 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Leaf blades more or less hairy, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule a fringe of hairs, Inflorescence terminal, Inflorescence a dense slender spike-like panicle or raceme, branches contracted, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence curved, twisted or nodding, Inflorescence spike linear or cylindric, several times longer than wide, Flowers bisexual, Spikelets pedicellate, Spikelets dorsally compressed or terete, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets with 2 florets, Spikelet with 1 fertile floret and 1-2 sterile florets, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating below the glumes, Spikelets all subtended by bristles, Spikelet bristles 1-3 , Spikelet bracts bristles not disarticulating with spikelets, Glumes present, empty bracts, Glumes 2 clearly present, Glumes distinctly unequal, Glumes shorter than adjacent lemma, Glume equal to or longer than spikelet, Glumes 3 nerved, Glumes 4-7 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma similar in texture to glumes, Lemma becoming indurate, enclosing palea and caryopsis, Lemma 5-7 nerved, Lemma glabrous, Lemma rugose, with cross wrinkles, or roughened, Lemma apex acute or acuminate, Lemma awnless, Lemma margins thin, lying flat, Lemma straight, Palea present, well developed, Palea shorter than lemma, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis.

Setaria viridis is a species of grass known by many common names, including green foxtail, green bristlegrass, and wild foxtail millet. It is sometimes considered a subspecies of Setaria italica. It is native to Eurasia, but it is known on most continents as an introduced species and is closely related to Setaria faberi, a noxious weed. It is a hardy grass which grows in many types of urban, cultivated, and disturbed habitat, including vacant lots, sidewalks, railroads, lawns, and at the margins of fields. It is the wild antecedent of the crop foxtail millet.

This is an annual grass with decumbent or erect stems growing up to a meter long, and known to reach two meters or more at times. The leaf blades are up to 40 centimeters long and 2.5 wide and glabrous. The inflorescence is a dense, compact, spikelike panicle up to 20 centimeters long, growing erect or sometimes nodding at the tip only. Spikelets are 1.8–2.2 mm long. Each is subtended by up to three stiff bristles. Its fertile lemmas are finely cross-wrinkled.

Setaria viridis is often confused with S. faberi, (Chinese or Giant Foxtail), which has sparse, soft hairs on the leaves and a nodding inflorescence. Setaria viridis is closely related to S. italica (Foxtail Millet), which has larger spikelets about 3 mm long and usually smooth, shiny upper lemmas. Foxtail Millet was cultivated in China by 2700 BC and during the Stone Age in Europe.

Setaria viridis has been proposed as a model to study C4 photosynthesis and related bioenergy grasses. It has a short life cycle (6–8 weeks), is transformable and is currently being sequenced. Genetic resources are currently being developed by a number of groups. A method to break the prolonged seed dormancy has been discovered recently and all these could contribute towards making S. viridis a choice monocot genetic model system.