Setaria Beauv.
Setaria is a relatively large genus of ca. 130 species (Mabberley 2008). Most are confined to warm-temperate to tropical regions, especially in Africa, Asia and South America. The residence status of some of the taxa in Belgium (native / archaeophyte / neophyte) is still unclear and requires additional studies; this surely holds true for Setaria pumila, S. verticillata, S. verticilliformis and S. viridis. As they have always been found exclusively in artificial, man-made habitats they are treated here, at least for the time being, as non-native.
The specific boundaries between some of the taxa treated here are sometimes blurred and some are perhaps better considered at subspecific or even varietal rank. This applies to the Setaria verticillata-group (here represented by S. adhaerens, S. verticillata and S. verticilliformis) and the Setaria viridis-group (represented by S. italica and S. viridis) (see below).
1 Bristles below spikelets retrorsely scabrous, strongly adherent (especially at maturity). Inflorescence axis scabrous with minute spinules. Annual grasses === 2
1 Bristles below spikelets antrorsely scabrous, not adherent. Inflorescence axis hairy or scabrous. Annual or perennial grasses === 3
2 Margin of leaf sheaths glabrous === 1. Setaria adhaerens
2 Margin of leaf sheaths with long hairs === 7. S. verticillata
3 Upper lemma strongly transversely rugose. Bristles usually yellowish, always at least 4 below each spikelet === 4
3 Upper lemma smooth to rugose (never strongly so). Bristles very rarely yellowish (green, more rarely purplish), usually 3 below each spikelet === 6
4 Annual grasses. Spikelets 3-3,4 mm long (common) === 5. S. pumila
4 Perennial grasses. Spikelets 2-3 mm long (rare) === 5
5 Inflorescence very long and slender, up to 25 cm long === 6. S. sphacelata
5 Inflorescence shorter, usually ca. 5-8 cm long === 4. S. parviflora
6 Inflorescence axis scabrous with minute spinules === 8. S. verticilliformis
6 Inflorescence axis hairy === 7
7 Leaf blades softly long hairy adaxially. Upper glume ca. ¾ as long as upper lemma. Upper lemma rugose. Panicle nodding from near the base at maturity === 2. S. faberi
7 Leaf blades glabrous. Upper glume ¾ to as long as the upper lemma. Upper lemma smooth or rugose. Panicle erect or nodding from near the base at maturity === 8
8 Upper lemma smooth and shining, exposed at maturity (upper glume slightly shorter than upper lemma), not falling off at maturity. Spikelets up to 3 mm. Panicle often nodding from near the base at maturity, often very large and thick, sometimes branched === 3. S. italica
8 Upper lemma rugose and dull, not exposed at maturity (upper glume equaling upper lemma), falling off at maturity. Spikelets smaller, up to 2,2 mm. Panicle erect, rarely slightly nodding (var. major), small to moderately large === 9. S. viridis
Additional alien: Setaria dielsii R.A.W. Herrmann (Aus., wool alien).
Literature:
Amigo J., Bujan M. & Romero I. (1991) Révision taxonomique du genre Setaria (Gramineae) dans la Péninsule Ibérique. Bull. Soc. Bot. Fr., Lettres Bot. 138(2): 155-165.
Auquier P. (1979a) Le genre Setaria Beauv. (Poaceae) en Belgique et au Grand-Duché de Luxembourg. Lejeunia N.S. 97: 1-13.
Auquier P. (1979b) Les concepts de Dumortier dans le genre Setaria Beauv. (Poaceae). Bull. Jard. Bot. Nat. Belg. 49: 427-433.
Banfi E. (1989) Osservazioni sulle specie italiane del genere Setaria P. Beauv. (Poaceae). Atti Soc. Ital. Sci. Nat. Museo Civ. Storia Nat. Milano 130(13): 189-196.
Conert H.J. (ed.) (1998) Gustav Hegi Illustrierte Flora von Mitteleuropa. Band I, Teil 3 Poaceae (3.Auflage). Parey Buchverlag, Berlin: XXVII + 898 p.
Dekker J. (2003) The foxtail (Setaria) species-group. Weed Science 51: 641-656. [available online at: http://agron-www.agron.iastate.edu/~weeds/PDF_Library/Jax_Pubs/FoxWSciRe...
Jauzein P. (1988) Remarques sur le genre Setaria P. Beauv. en France. Monde Pl. 431: 9-12.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Morrone O., Aliscioni S.S., Veldkamp J.F., Pensiero J.F., Zuloaga F.O. & Kellogg E.A. (2014) Revision of the Old World Species of Setaria (Poaceae: Panicoideae: Paniceae). Syst. Bot. Monogr. 96: 161 p.
Pensiero J.F. (1999) Las especies sudamericanas del género Setaria (Poaceae, Paniceae). Darwiniana 37(1-2): 37-151. [available online at: http://www.ojs.darwin.edu.ar/index.php/darwiniana/article/view/345]
Rominger J.M. (1962) Taxonomy of Setaria (Gramineae) in North America. Illinois Biol. Monogr. 29: 1-132. [available online at: http://archive.org/details/taxonomyofsetari29romi]
Rominger J.M. (2003) Setaria. In: Barkworth M.E. & al. (eds.), Flora of North America north of Mexico, vol. 25: 539-558. Oxford University Press, New York-Oxford.
Rostański K. (1996) Bristle-grasses (Setaria, Poaceae) in Poland. Fragm. Flor. Geobot. 41(2): 507-512.
Shouliang C. & Phillips S.M. (2006) Setaria. In: Zhengyi W. & Raven, P.H. (eds.), Flora of China, vol. 22: 531-537. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis.
Webster R.D. (1993) Nomenclature of Setaria (Poaceae: Paniceae). Sida 15: 447-489.