Try to make your search as simple as possible:
Tripsacum will find all items including that sequence of letters.
Search results for "Tripsacum":
"Tripsacum cylindricum" - Mnesithea cylindrica
"Tripsacum fasciculatum" - Tripsacum laxum
"Tripsacum floridanum" - Tripsacum dactyloides dwarf form
"Tripsacum hermaphroditum" - Anthephora hermaphrodita