Panicum coloratum L. (Afr.) – A very rare and ephemeral alien. Recorded in 1901 and 1916 as a wool alien in the valley of river Vesdre near Verviers (Verloove 2001). In 1986 a single individual was recorded on the gravelly banks of river Maas in Meeswijk. This record was possibly also related with the former wool processing activities upstream.
In Belgium this species has been confused with Panicum repens L., another perennial with staminate lower florets. The latter, however, has long creeping rhizomes, distichously arranged leaves and its lower glume is rounded to truncate at apex. Confusion is also possible with Panicum virgatum L. but all floral parts of the latter are usually larger, lower glume vs. upper glume ratio is different, lower paleas are markedly hastate and spikelets are strongly gaping at maturity. In western Europe Panicum virgatum probably always is an escaped ornamental while P. coloratum is a weedy species.
Panicum coloratum itself is an exceedingly variable species and its taxonomy is not resolved yet (see for instance Gibbs Russell & al. 1991). The South African Panicum stapfianum Fourc., another member of this aggregate, was formerly recorded as a wool alien in the British Isles (Ryves & al. 1996).
Panicum coloratum is a valuable forage grass and widely cultivated in the (sub-) tropics. A future naturalization in parts of southern Europe is not unlikely (e.g. Acedo & al. 2011).
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Selected literature:
Acedo C., Molina A., Alonso A. & Llamas F. (2011) Notas taxonómicas y corológicas para la flora de la Península Ibérica: 179. Novedades corológicas para la flora ibérica. Lagascalia 31: 233-239. [available online at: http://institucional.us.es/revistas/lagascalia/31/notas.pdf]
Gibbs Russell G.E., Watson L., Koekemoer M., Smook L., Barker N.P., Anderson H.M. & Dallwitz M.J. (1991) Grasses of southern Africa. Memoirs of the Botanical Survey of South Africa n° 58: IX + 437 p.
Lloyd D.L. & Thompson J.P. (1978) Numerical analysis of taxonomic and parent-progeny relationships among Australian selections of Panicum coloratum. Queensl. J. Agric. Anim. Sci. 35(1): 35-46.
Pritchard A.J. & De Lacy I.H. (1974) The cytology, breeding system and flowering behaviour of Panicum coloratum. Austral. J. Bot. 22(1): 57-66.
Ryves T.B., Clement E.J. & Foster M.C. (1996) Alien grasses of the British Isles. BSBI, London: XX + 181 p.
Verloove F. (2001) A revision of the genus Panicum (Poaceae, Paniceae) in Belgium. Syst. Geogr. Pl. 71: 53-72.