12. Rumex stenophyllus Ledeb. (syn.: R. odontocarpus Sándor ex Borb.) (E-Eur., temp. As.) – A regular alien, known at least since 1904 but long overlooked due to confusion with R. xpratensis (Verloove 2008). Formerly recorded as an ephemeral wool alien in the Vesdre valley. In the past decades increasingly found, especially near grain storages in port areas. Locally obviously naturalised, for instance in the ports of Gent (numerous places) and Antwerpen (Amerikadok, Kattendijkdok). Usually found in road verges, near unloading quays or on dumps, often in abundance. Occasionally also recorded without obvious link with cereals, for instance in a clay pit in Marke (2009), in a worked-up road verge in Lauwe (2009), sandraised site in Zeebrugge (2012), etc. In 2011 also repeatedly seen on the gravelly banks of river Maas in Dilsen-Stokkem. Also known in relative abundance by a roadside in Drongen (Drongensesteenweg) since several years. Rumex stenophyllus is still poorly known and doubtlessly overlooked elsewhere in Belgium (Verloove 2013).
An enumeration of all Belgian records and distinguishing features for Rumex stenophyllus and R. xpratensis are provided by Verloove (2008, 2013).
Jansen P. & Wachter W.H. (1913) Floristische aanteekeningen VII. Rumex. Nederl. Kruidk. Arch. 1913: 91-140.
Ludwig W. (1988) Der Schmalblättrige Ampfer (Rumex stenophyllus Ledeb.) adventiv in Hessen. Hess. Flor. Briefe 37(1): 12-13.
Müller R. & Kallen H.W. (1988) Rumex stenophyllus Ledeb. an der Elbe in Niedersachsen. Flor. Rundbr. 21(2): 80-85.
Verloove F. (2008) Twee miskende Rumex-taxa in België. Dumortiera 95: 4-8.
Verloove F. (2013) Verder onderzoek binnen het genus Rumex (Polygonaceae) in België. Dumortiera 102: 3-9. [available online at: http://www.br.fgov.be/DUMORTIERA/DUM_102/Dum_102_3-9_Rumex_Verloove.pdf]