Butterfly flag is native to southeastern Australia and Tasmania (where it is also known as white iris). If you're browsing online for more information on this species, please note that the name Diplarrena has a variant spelling, Diplarrhena. I've opted to use the first as it is in use by both the Australian National Botanic Garden's entry on Diplarrena moraea and the New South Wales Flora Online.

This photograph was taken at the end of May last year in the Australasian section of the Alpine Garden.