Try to make your search as simple as possible:
Krebsia will find all items including that sequence of letters.
Search results for "Krebsia":
"Gazania krebsiana O P" - Gazania Orange Peacock rs
"Krebsia divaricata" - Lotononis divaricata
"Krebsia stricta" - Lotononis stricta
"Rhus krebsiana" - Searsia krebsiana