pbs Digest, Vol 61, Issue 15 I. tectorum
Adam Fikso (Sun, 24 Feb 2008 21:35:28 PST)

Iris tectorum DOES grow on roofs, or did. There is at least one old B & W
photograph in an iris book showing it growing on tile roofs in Japan. I
cannot recall the book's author or title. But it is there. If memory
serves--both author and title were British. Last time I saw it was about 50
years ago and was at that time, available in the Chicago area.