2. Polygonum arenarium Waldst. et Kit. subsp. pulchellum (Loisel.) D.A. Webb et Chater (syn. P. pulchellum Loisel.) (Medit.) – A very rare and usually ephemeral alien. Recorded in 1943 in Brussel (waste land) and in 1970 at two locations near Turnhout (dump and by canal). The latter two records were possibly associated with cereals. In 2009 discovered in extreme abundance in and near a talc deposit adjoining the Zuid-Willemsvaart in Rekem (initially as P. rurivagum). (see also http://waarnemingen.be/soort/view/120791). Here, Polygonum arenarium is spreading to adjacent road verges, waste land and orchards. It must have been introduced years ago and is now (as for 2020) quite frequent. At the very same location Parapholis incurva is also well-established. Both were probably introduced with talc, possibly from Egypt or Pakistan.
Polygonum arenarium, P. bellardii, P. argyrocoleon and P. patulum are much alike and likely to be confused. All are characterised by much reduced leaves in the upper part of the inflorescence. Out of these, Polygonum arenarium is easily distinguished by its very conspicuous, patent (usually bright pink, more rarely whitish) “petaloid” tepals.
The plants from Rekem slightly deviate from the usual circumscription of Polygonum arenarium, especially in that the leaves are very narrow (nearly acicular). A molecular study by Dr. Olga Yurtseva was recently carried out and proved that this population represents a hybridogenous taxon, apparently Polygonum arenarium (a race from the Black Sea-coast) x P. neglectum (the latter probably being a hybrid of P. patulum and P. aviculare s.l.).
Selected literature:
Lawalrée A. (1953b) Contribution à l’étude de la flore adventice de la Belgique. Bull. Soc. Roy. Bot. Belg. 86: 137-143.