Why is iris tectorum called "roof iris"? This Chinese native was was first observed in the late 1800's in Japan, where a Russian scientist found it growing in the thatched roofs of farmers.  The Japanese farmers weren't growing it for the flowers but for the roots, which were ground to a white powder that geisha girls used for their traditional make-up.

Unlike most iris, this variety does almost as as well in sun as in shade.