Try to make your search as simple as possible:
Heracleum will find all items including that sequence of letters.
Search results for "Heracleum":
"Heracleum cyclocarpum var. pon" - Heracleum ponticum
"Heracleum laciniatum" - Heracleum stevenii
"Heracleum villosum" - Heracleum stevenii