Try to make your search as simple as possible:
Adenium will find all items including that sequence of letters.
Search results for "Adenium":
"Adenium arabicum" - Adenium obesum
"Adenium coetaneum" - Adenium obesum
"Adenium honghel" - Adenium obesum
"Racosperma acradenium" - Acacia acradenia
"Racosperma macradenium" - Acacia macradenia