Epimedium L.
Epimedium is a genus of about 25 species. Most representatives are native in the Mediterranean area (southern Europe, NW-Africa and SW-Asia) and temperate Asia, eastwards to China and Japan. Many of the species are cultivated as ornamentals. Stearn (1989) enumerates no less than 18 species and hybrids but only few are widespread in cultivation. Up to present two species have been recorded as escapes in Belgium.
1. Stem leafless (all leaves basal). Leaflets 3-5. Inflorescence a glabrous or sparsely glandular raceme. Flowers ca. 16-20 mm across. Inner sepals (petal-like) yellow === Epimedium pinnatum subsp. colchicum
1. Leaves basal and cauline (at least 1 cauline leaf). Leaflets usually 9. Inflorescence compound and densely glandular. Flowers 9-13 mm across. Inner sepals reddish === E. alpinum
Literature
Desmet Y. (2010) Soort zkt. grens: Epimedium (Berberidaceae): Soorten zonder grenzen? Thesis, University of Ghent, Belgium.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Stearn W.T. (1938) Epimedium and Vancouveria (Berberidaceae), a monograph. J. Linn. Bot. Soc. 51: 409-535.
Stearn W.T. (1989) Epimedium. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 3. Cambridge University Press, Cambridge: 389-393.