Try to make your search as simple as possible:
Thevetia will find all items including that sequence of letters.
Search results for "Thevetia":
"Thevetia ahouai" - Thevetia nitida
"Thevetia cuneifolia" - Thevetia ovata
"Thevetia neriifolia" - Thevetia peruviana
"Thevetia nitida" - Thevetia ahouai