Vincetoxicum Wolf
The generic limits of Vincetoxicum and its taxonomy are unclear. According to Knees (2000b) it counts 15 species in Eurasia whereas Mabberley (2008) accepts 70 species for the same area. One species, Vincetoxicum hirundinaria Med., is a rare and local native in Belgium.
All Belgian collections of Vincetoxicum were revised by Markgraf in 1968.
1. Corolla greenish-white, the lobes with curved hairs or glabrous on the upper surface. Calyx lobes linear (native) === V. hirundinaria
1. Corolla dark purple, the lobes glabrous or with straight hairs on the upper surface. Calyx lobes ovate-lanceolate === 2
2. Corolla lobes with straight hairs on the upper surface === 1. Vincetoxicum nigrum
2. Corolla lobes glabrous on the upper surface === 2. V. rossicum
Literature
Knees S.G. (2000b) Vincetoxicum. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 53-54.
Lauvanger E.G. & Borgen L. (1998) The identity of Vincetoxicum in Norway. Nordic J. Bot. 18(3): 353-364.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Markgraf F. (1971) Beobachtungen an den europäischen Arten der Gattung Vincetoxicum. Bot. J. Linn. Soc. 64: 370-376.
Markgraf F. (1972) Vincetoxicum. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 3. Cambridge University Press, Cambridge: 71-73.