According to different taxonomic treatments, this genus includes 55 or 17 species, mainly in countries around the Mediterranean, Black and Caspian seas. Russian taxonomists consider there are 8 species in the FSU, all in the Caucasus. Only two species, C. coum Mill. and C. purpurascens Mill., also occur outside the Caucasus and they are known in cultivation. The others also are of interest for gardening.