Rumex hydrolapathum, Hudson

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1964, Flora Europaea - Volume 1. Lycopodiaceae to Platanaceae, Cambridge University Press : 86

32. R. hydrolapathum Hudson , Fl. Angl. ed. 2, 154 (1778).

Perennial up to 200 cm. Leaves flat, rigid, broadly lanceolate, tapering equally at both ends, lateral veins at a right angle with the midrib; basal leaves 4-5 times as long as wide. Pedicels stiff, c. 1 i times as long as the valves. Valves triangular, each with a distinct fusiform tubercle. Nut 4-5-5 mm. 2« = 200. Marshes. Europe, except the south and extreme north; Makedonija. Au Be Br Bu Cz Da Fe Ga Ge Hb He Ho Hs Hu It Ju No Po Rm Rs (B, C, W, K, E) Su.

The hybrid with R. aquaticus ( R. heterophyllus C. F. Schultz , R. maximus Schreber , non C. C. Gmelin) is frequent in N.C. Europe and S. Scandinavia. It is similar in habit to R. hydrolapathum but has wider and shorter leaves, rounded or slightly cordate at the base, and valves of somewhat irregular development, in part larger and wider than in pure R. hydrolapathum . The hybrid with R. obtusifolius is rarer, but not infrequent in England and the Netherlands; it is easily distinguished by the distinct teeth near the base of the valves and by their rather long apex. All R. hydrolapathum hybrids are similar in habit to R. hydrolapathum .