As some one wrote, Louisiana irises are hardy in zone 5 in Rochester, NY. I've seen pictures of them encased in ice. They were fine the following spring.
LA irises like to have their rhizomes covered or they will sunburn and probably die. Unlike bearded iris, they like to be mulched.
They like water and will grow on the edge of a pond or in the pond. More information can be found at the Society for Louisiana Irises.
http://www.louisianas.org/
"Geisha Eyes"
This iris is growing in the pond.
