5. Polygonum bellardii All. (syn.: P. kitaibelianum Sadler) (Medit.) – A very rare and ephemeral alien. Formerly recorded as a wool alien in the Vesdre valley and at various other locations but much decreasing lately. By far the least rare of the Polygonum-species with an upright habit and still occasionally found, for instance in 2004 on a disused railway yard in Gent, in 2009 on disturbed soil (former dump) in a nature reserve in Knokke and on unloading quays for cereals in Moen in 2011 (canal Kortrijk-Bossuit) and in the Antwerp port area in 2015.
Polygonum bellardii is here treated in a narrow sense, excluding P. patulum. The latter is a SE-European species with much smaller flowers and fruits (fruit ca. 2-2,3 mm vs. 2,4-3 mm in Polygonum bellardii) and has only been found once in Belgium in 1915.
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Selected literature:
Raffaelli M.(1979) Contributi alla conoscenza del genere Polygonum L. 2. Polygonum bellardii All. Webbia 33: 327-342.