Urochloa ramosa (L.) T.Q. Nguyen (syn.: Brachiaria ramosa (L.) Stapf, Panicum ramosum L.) (trop. Afr., trop. As.) – An exceptional and ephemeral alien. A single individual was recorded as a pavement weed in Antwerpen in 2018.
Urochloa ramosa is widely cultivated as a short-duration crop (Veldkamp 1996), sometimes also as birdseed (Wipff & Thompson 2003). This can explain its occurrence in an urban habitat in Belgium. Although weedy and commonly grown, it has probably not been recorded before from Europe. It is a frequent weed elsewhere in the tropics and subtropics outside its native range, for instance in the southeastern United States (Wipff & Thompson 2003) and in parts of Australia (Webster 1987).
Urochloa ramosa is a very variable species. In Africa it is known to intergrade with related species such as U. deflexa (Schumach.) H. Scholz (Clayton & Renvoize 1982). The plants found in Antwerpen are characterized by glabrous spikelets, ca. 3.3 mm long, the upper of each pair on a pedicel about as long as the spikelet. Spikelets are more often slightly or distinctly puberulent and pedicels are often shorter. Plants found in Malesia and Australia always have shorter spikelets (up to 3 mm long) (Veldkamp 1996, AusGrass2 2018).
Selected references
Ashalatha V.N. & Nair V.J. (1993) Brachiaria Griseb. and Urochloa P. Beauv. (Poaceae) in India — a conspectus. Bull. Bot. Surv. India 35: 27–31.
AusGrass2 (2018) AusGrass2. Grasses of Australia. [available online at: http://ausgrass2.myspecies.info/content/urochloa]
Clayton W.D. & Renvoize S.A. (1982) Gramineae (part 3). In: Polhill R.M. (ed.), Flora of Tropical East Africa. A.A. Balkema, Rotterdam: 451-898.
Veldkamp J.F. (1996) Brachiaria, Urochloa (Gramineae-Paniceae) in Malesia. Blumea 41: 413-437. [available online at: http://www.repository.naturalis.nl/document/565314]
Webster R.D. (1987) The Australian Paniceae (Poaceae): 322 p. J. Cramer, Berlin and Stuttgart.
Wipff J.K. & Thompson R.A. (2003) Urochloa. In: Barkworth M.E. & al. (eds.), Flora of North America north of Mexico, vol. 25. Oxford University Press, New York-Oxford: 492-507.