2. Paspalum distichum L. [syn.: P. paspalodes (Michaux) Scribner, P. distichum subsp. paspalodes (Michaux) Thell.] (subtrop.) – A very rare and ephemeral alien. Recorded between 1950 and 1954 on a dump in Mechelen (Galgenberg), possibly as a birdseed alien. In 2016 and 2017 scattered individuals were observed near a grain mill at the Amerikadok in the Antwerp port area. In this locality it grew along with rice field weeds like Ammannia coccinea, Diplachne fusca subsp. fascicularis, Echinochloa oryzicola, Leersia oryzoides and others. It was most likely introduced as a contaminant in rice.
Interestingly, according to Des Moulins (1847) this species would have been recorded already in Belgium (Ostend port area) at the beginning of the 19th century.
Paspalum distichum is rather widely naturalised in parts of France and obviously expands to the north (for an up-to-date distribution map, see: http://www.tela-botanica.org/eflore/BDNFF/4.02/nn/48018/export/pdf). A future naturalisation in suitable habitats (damp meadows, by streams, pond margins, etc.) in Belgium is not unlikely. Additional information on its potential in western Europe is available at: http://www.q-bank.eu/Plants/Factsheets/Paspalum%20distichum%20NL.pdf.
The closely related Paspalum vaginatum Swartz has been claimed for Belgium (see Lambinon & al. 2004), perhaps as a result of confusion with P. distichum. Both are easily distinguished on upper glume characters: these are glabrous in Paspalum vaginatum and pubescent in P. distichum. Moreover, Paspalum vaginatum is often confined to saline habitats and less likely to occur as an alien.
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Selected literature:
Des Moulins Ch. (1847) Sur une graminée de l'Amérique septentrionale, naturalisée depuis 1820 dans les environs de Bordeaux. Actes de la Société Linnéenne de Bordeaux 15: 155-172. [available online at: https://www.biodiversitylibrary.org/item/102891#page/153/mode/1up]
Hare A.D.R. (1985) Paspalum paspaloides (Michaux) Scribner in East London. BSBI News 39: 10-11.
Lambinon J. (1957) Contribution à l’étude de la flore adventice de la Belgique. I. Adventices rares ou nouvelles pour la Belgique. Bull. Soc. Roy. Bot. Belg. 89: 85-100.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H. (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.