9. Eragrostis virescens J. Presl (syn.: E. mexicana (Hornem.) Link subsp. virescens (J. Presl) S.D. Koch et Sánchez Vega) (S-Am.) – A rare alien, usually ephemeral but sometimes very persistent and possibly becoming more or less naturalised locally. Probably collected for the first time in 1947 as a wool alien in the Vesdre valley. Soon afterwards (1954) also in the port of Antwerpen. Both collections were only recently recognised as Eragrostis virescens. More recently recorded several times: first on the unloading quay for cereals at the Kattendijkdok in the port of Antwerpen in 1997 (Verloove & Vandenberghe 1998). Since 1999 furthermore known in relative abundance from the Groothandelsmarkt (cracks in pavement), also in Antwerpen; here more or less established (although often destroyed by weed killer). In 2013 also seen near a plant nursery in Oostham. All these records pertain to the typical subspecies (subsp. virescens), the usual alien in Europe.
However, the Belgian populations belong to two distinct entities. An aberrant population, discovered in 1999 as a weed in plantations near a warehouse in Gent, turned out to belong to an undescribed subspecies, subsp. verloovei Portal (Portal 2002b). Both subspecies are distinguished as follows:
- Pulvini (axes) of the primary inflorescence branches pilose. Lateral pedicels often longer than their spikelets. Spikelets dark greyish, opaque. Inflorescence a diffuse panicle === subsp. verloovei
- Pulvini of the primary inflorescence branches glabrous. Lateral pedicels shorter than their spikelets. Spikelets pale greenish to yellowish, hyaline. Inflorescence a more contracted panicle === subsp. virescens
Subspecies verloovei persisted in Gent at least till 2004 but apparently disappeared after infrastructural works. It was furthermore discovered in small number on waste land in Gierle in 2009.
This subspecies is rather distinct and only shares the caryopsis with a deep ventral groove and the narrow spikelets with Eragrostis virescens s.str. If the several different taxa within the Eragrostis mexicana-complex are maintained at specific rank, it might as well be given species rank.
Eragrostis virescens is usually said to be totally non-glandular. However, glandular tissue is sometimes present beneath the nodes.
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Selected literature:
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.
Martini F. & Scholz H. (1998) Eragrostis virescens J. Presl (Poaceae), a new alien species for the Italian flora. Willdenowia 28: 59-63.
Portal R. (2002b) Eragrostis pilosa subsp. felzinesii et Eragrostis virescens subsp. verloovei (Poaceae: Chloridoideae, Eragrostideae) deux nouvelles sous-espèces pour l’Europe. Bull. Soc. Bot. Centre-Ouest N.S. 33: 3-8.
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.
Verloove F. & Vandenberghe C. (1998) Nieuwe en interessante voederadventieven voor de Belgische flora, hoofdzakelijk in 1997. Dumortiera 72: 18-36.