7. Rumex obtusifolius L. (Eur., W-As.) – A very common native species. Very variable, especially with regard to characters of valves. The following subspecies occur in Belgium: subsp. obtusifolius, subsp. sylvestris (Wallr.) Čelak. (syn.: R. sylvestris Wallr.) and subsp. transiens (Simonk.) Rech. f. They are distinguished as follows:
1. Valves distinctly lingulate, almost entire to crenate with some short teeth at base. All valves with a well-developed tubercle === subsp. sylvestris
1. Valves triangular-ovate, with distinct teeth, at least some subulate (native) === 2
2. Only one valve with a well-developed tubercle. Valves up to 6 mm long, with 1-4 prominent subulate teeth === subsp. obtusifolius
2. All valves with a tubercle, tubercles sometimes unequally developed. Valves less than 5 mm long, with 1-3 shorter teeth === subsp. transiens
Subsp. sylvestris – native in eastern Europe – is poorly known and its distribution pattern and degree of naturalization in Belgium are unknown. It was found from time to time between 1953 and 1972 and is probably overlooked. In 2012 is was seen on a worked-up dike of river Schelde near Antwerpen and in 2013 alongside river Maas in Herbricht.
Residence status of subsp. transiens is somewhat doubtful. Its main distribution area lies east of Belgium but according to Duvigneaud (1973) it is native in southeastern Belgium as well, especially in riparian habitats.
Herbarium specimen subsp. sylvestris
Duvigneaud J. (1973) Rumex obtusifolius subsp. transiens indigène en Belgique et dans le département des Ardennes (France). Nat. Mosana 26(3): 70-74.
Raycheva T. (2009) Critical reassessment of the distribution of some taxa of Rumex subgenus Rumex (Polygonaceae) in Bulgaria – 2. Phytol. Balcan. 15(2): 155-169.
Rechinger K.H. (1932) Vorarbeiten zu einer Monographie der Gattung Rumex, 1. Beih. Bot. Centralbl. 49(2): 1-132.