Try to make your search as simple as possible:
Epimedium will find all items including that sequence of letters.
Search results for "Epimedium":
"Epimedium alpinum var. pubiger" - Epimedium pubigerum
"Epimedium Frohnleiten" - Epimedium perralchicum x
"Epimedium hexandrum" - Vancouveria hexandra