Bromus madritensis L. (syn.: Anisantha madritensis (L.) Nevski) (Medit.) – A rare but probably increasing alien. Probably first collected in 1848 (without further details). Formerly primarily introduced with wool waste in the Vesdre valley. In more recent times usually associated with grain importation. Up to present always ephemeral but possibly becoming naturalised in urban areas. Discovered as a pavement weed in 2006 in the city of La Louvière (Verloove 2006b) and known, in quantity and at least since 1998, from a railway track in the port of Gent. A large, apparently naturalized population was also discovered in a railway yard in Borgerhout (Antwerpen) in 2014. Analogous records are available for the Netherlands as well (Denters 2004).
Many distinguishing features provided in literature are variable and hence unreliable. Lemmas can be either densely pubescent (var. ciliatus Guss.) as well as glabrous. Stems are usually told to be glabrous beneath the inflorescence but can be short-hairy as well. Plants with such features have been segregated as subsp. kunkelii Scholz (Scholz 1981a) but are now generally considered as conspecific with B. rubens (see Sales 1994). Esnault (1984) already showed that much of the variability of this species is related with environmental conditions and of no taxonomical value.
Confusion is most likely with Bromus diandrus. With this species it shares the fairly large, shortly pedicellate spikelets.
Many of the Belgian and Dutch naturalised populations belong to var. ciliatus (see also van der Meijden 2005), but at least the plants from the port of Gent have glabrous spikelets.
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Selected literature:
Denters T. (2004) Stadsplanten. Veldgids voor de stad. Fontaine Uitgevers, ‘s-Graveland: 432 p.
Esnault M.-A. (1984) Etudes sur la variabilité morphologique de Bromus madritensis. Phytomorphology 34: 91-99.
Oja T. (2002) Genetic divergence and interspecific differentiation in the Bromus madritensis complex (Poaceae) based on isozyme data. Biochem. Syst. Ecol. 30(5): 433-449.
Rivas Ponce M.A. (1988) Nuevos datos para la diagnosis de Bromus rubens L. y B. madritensis L. (Poaceae). Lagascalia 15(1): 89-93.
Sales F. (1994) A reassessment of the Bromus madritensis complex (Poaceae): a multivariate approach. Isr. J. Pl. Sc. 42: 245-255.
Scholz H. (1981a) Bemerkungen über Bromus madritensis und B. rubens (Gramineae). Willdenowia 11: 249-258.
Van der Meijden R. (2005) Heukels’ Flora van Nederland (23e druk). Wolters-Noordhoff, Groningen: 685 p.
Verloove F. (2006b) Twee nieuwe stadsgrassen in België: Bromus madritensis en Polypogon viridis. Dumortiera 90: 24-26.