1. Setaria adhaerens (Forssk.) Chiov. [syn.: S. verticillata var. aparine (Steud.) Aschers. et Schweinfurth, S. aparine (Steud.) Chiov.] (trop.) – A very rare and probably always ephemeral alien. Formerly occasionally recorded as a wool alien in the valley of river Vesdre, at least between 1929 and 1948 (as Setaria verticillata). Most recent records seem to be associated with cereals. However, Setaria adhaerens is by far best known today from plant nurseries. It is one of the more typical introductions in containers with olive trees and palms from southern Europe (Hoste & al. 2009). It is possibly more or less naturalised locally. Records from port-areas, near grain elevators and granaries, unloading quays, along highways,… are often much less typical and possibly rather belong with Setaria verticillata. Perhaps under-recorded and still widely confused with Setaria verticillata s.str.
Typical plants of Setaria adhaerens are readily distinguished from S. verticillata by the total absence of hairs on the margins of the leaf sheaths. Some specimens however are more or less intermediate (presence of some scattered hairs, even on plants with all other leaf sheaths completely glabrous!). According to some authors (see for instance Rominger 2003) Setaria adhaerens should have strigose leaf surfaces (vs. scabrous leaf surfaces in S. verticillata). Indeed, some collections are characterised by scattered hairy leaf surfaces but others, with leaf sheath margins completely glabrous, have scabrous leaf surfaces. In addition to leaf sheath characters, Setaria adhaerens typically has a much shorter and more or less conical inflorescence (obviously widest at base) and its bristles are remarkably longer than in S. verticillata.
The distinction of Setaria adhaerens and S. verticillata appears to be problematic, at least in Belgium, and the former is perhaps a mere tropical variety of the latter. A revision of Old World Setaria considers S. adhaerens and S. verticillata as conspecific (Morrone & al. 2014).
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Selected literature:
Belo-Correia A.L. & Costa M.F. (1989) Setaria verticillata (L.) P. Beauv. e Setaria adhaerens (Forsskaol) Chiov.-1. Bol. Soc. Brot., Sér. 2 62: 289-290.
Danin A. & Scholz H. (1997) On the occurrence of two taxa of the Setaria verticillata complex in Israel and the Sinai. Willdenowia 27(1-2): 177-179.
Hoste I., Verloove F., Nagels C., Andriessen L. & Lambinon J. (2009) De adventievenflora van in België ingevoerde mediterrane containerplanten. Dumortiera 97: 1-16.
Ludwig W. (1996) Zu Setaria adhaerens (Forssk.) Chiov.: Literaturhinweise anlässlich eines Fundes in Frankfurt a.M. Hessische Floristische Briefe 45(2): 26-27.
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.
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.