3. Eragrostis mexicana (Hornem.) Link (Am.) – A very rare and ephemeral alien. Recorded between 1822 and 1824 on the sandy banks of river Meuse in Herstal and even claimed to be naturalised at that time (as Eragrostis pilosa). In the 1940’s and 1950’s rarely observed as a wool alien in the Vesdre valley near Verviers. Exceptionally seen elsewhere, apparently for the last time in 1955 near Leuven (Wilsele).
Eragrostis mexicana has long been confused with E. pilosa in Belgium although both are not related. The former has caryopses with a distinct ventral groove and is furthermore distinguished by a more open, few-flowered panicle. With Eragrostis neomexicana and E. virescens it forms the E. mexicana-complex. Several recent authors tend to adopt a rather broad species concept and only recognise one variable species (Peterson 2003). However, in Europe the distinction of the micro-species usually appears to be without difficulty (see Portal 2002a). Eragrostis mexicana is readily distinguished from both E. neomexicana and E. virescens by the absence of glandular tissue below the nodes and the open, few-flowered inflorescence.
Koch S.D. & Sánchez Vega I. (1985) Eragrostis mexicana, E. neomexicana, E. orcuttiana, and E. virescens: the resolution of a taxonomic problem. Phytologia 58(6): 377-381.
Peterson P.M. (2003) Eragrostis. In: Barkworth M.E. & al. (eds.), Flora of North America north of Mexico, vol. 25: 65-105. Oxford University Press, New York-Oxford.
Portal R. (2002a) Eragrostis de France et de l’Europe occidentale. Vals près Le Puy: 431 p.
Sánchez Vega I. & Koch S.D. (1988) Estudio biosystemático de Eragrostis mexicana, E. neomexicana, E. orcuttiana, y E. virescens (Gramineae: Chloridoideae). Bol. Soc. Brot. 48: 95-112.