Try to make your search as simple as possible:
Peniocereus will find all items including that sequence of letters.
Search results for "Peniocereus":
"Peniocereus diguetii" - Peniocereus striatus
"Peniocereus diguetii I M" - Peniocereus striatus Isla Magdalena
"Peniocereus serpentinus" - Disocactus flagelliformis