There are two types of spring Crocuses: the species and the hybrids, whch are generally listed as selections of C.vernus. The former are notable for their unusual coloration, the latter for their large flowers. Species Crocuses generally bloom earlier than the hybrids, so by using both kinds, you pro-long the season. The bulbs (properly, corms) multiply rapidly and can be planted anywhere a dash of color is wanted.