Try to make your search as simple as possible:
Spinifex will find all items including that sequence of letters.
Search results for "Spinifex":
"Cenchrus spinifex" - Cenchrus incertus
"Hibiscus spinifex" - Pavonia spinifex
"Spinifex hirsutus" - Spinifex sericeus cs (S.hirsutus)
"Spinifex hirsutus" - Spinifex sericeus bs