3. Polypogon viridis (Gouan) Breistr. [syn.: P. semiverticillata (Forssk.) Hyl., Agrostis semiverticillata (Forssk.) C. Christens., A. verticillata Vill., A. viridis Gouan] (Medit.) – Formerly an exceptional and casual wool alien in the Vesdre valley, last seen in 1939. Between 1958 and 1967 occasionally seen on a dump near Mechelen, perhaps as a birdseed alien. Recently much increasing and becoming naturalised in urban areas in many cities in Flanders, for instance in Aalst, Antwerpen, Blankenberge, Brugge, Gent, Oostende,… (surely still widely overlooked elsewhere). Commonly found as a pavement weed, against foot of walls, temporarily damp ruderal areas,… (see Verloove 2006 for a recent account for Flanders). Also much increasing as a troublesome weed in plant nurseries, for instance in an abandoned nursery in Boechout in 2007. Also regularly recorded in containers (Hoste & al. 2009). More rarely seen in rather remote localities without obvious vector of introduction (possibly as a result of roadworks or introduced by waterfowl) (see for instance: Duvigneaud & Saintenoy-Simon 1999 for a record in northern France, close to the Belgian frontiers).
In general habit, Polypogon viridis much more resembles Agrostis than Polypogon and it might often pass unrecorded. It is easily distinguished from Agrostis by spikelets that disarticulate below the glumes (glumes persistent in Agrostis).
Polypogon viridis is one of the most striking examples of Mediterranean species that recently increasingly occur in urban, climatologically favourable habitats in western Europe (see also Savelsbergh 2004, van der Meijden 2005, Stace 2010, etc.). According to Burton (2005) in London it now is “all over the place” and “an urban weed in many other southern English towns as well”.
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Selected literature:
Burton R. (2005) Foreign grasses in London streets. BSBI News 100: 48-49.
Duvigneaud J. & Saintenoy-Simon J. (1999) Polypogon viridis à la mare à Goriaux. Adoxa 24-25: 47-48.
Hoffer-Massard F. (2012) Polypogon viridis (Gouan) Breitsr. : encore une nouveauté en Suisse romande. Bulletin du Cercle vaudois de botanique 41: 99-100. [available online at: http://doc.rero.ch/record/203205?ln=fr]
Hoste I., Verloove F., Nagels C., Andriessen L. & Lambinon J. (2009) De adventievenflora van in België ingevoerde mediterrane containerplanten. Dumortiera 97: 1-16.
MacRoberts M.H., MacRoberts B.R. & Allen C.R. (2020) Polypogon viridis (Poaceae): New to Louisiana. Phytoneuron 2020-73: 1-4. [available online at: http://www.phytoneuron.net/2020Phytoneuron/73PhytoN-Polypogonviridis.pdf]
2020-73: 1–4.
Savelsbergh E. (2004) Agrostis semiverticillata (Forsk.) Hyl. (= Polypogon viridis (Gouan) Breistr.) seit mehr als fünf Jahren in Aachen-Burtscheid (TK 25 5202/233). Flor. Rundbr. 38(1-2): 15-17.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Van der Meijden R. (2005) Heukels’ Flora van Nederland (23e druk). Wolters-Noordhoff, Groningen: 685 p.
Verloove F. (2006) Catalogue of neophytes in Belgium. Scripta Botanica Belgica 39: 89 p.