Try to make your search as simple as possible:
Aira will find all items including that sequence of letters.
Search results for "Aira":
"Aira caerulea" - Molinia caerulea
"Aira cespitosa" - Deschampsia cespitosa
"Aira cristata" - Koeleria macrantha comm
"Aira flexuosa" - Deschampsia flexuosa
"Aira macrantha" - Koeleria macrantha comm