I got this iris at a nursery where it was labelled as Iris sibirica. After much waffling I believe it's actually Iris virginica. It has much wider foliage than typical Siberian iris and is much more vigorous and happy in wet conditions than Siberian iris that I have tried here. It's a very strong bloomer -- one mature clump looks like a bouquet of flowers.
Iris virginica is a water iris native to the Southeast. It's very easy to grow from seed: cold stratify the seeds for 3 months then plant in pots in the shade. I've started countless seedlings -- all of which are various shades of lavender -- from the original plant. Seedlings generally bloom the year after germination.
Iris virginica, spiderwort and Gulf Coast Penstemon with big perennial bed in background. I hope this picture doesn't make the garden appear too weedy, because it wasn't, although I was in the process of pulling weeds by the handful in the bed across the driveway from it! ;) The drive needed mowing and there was Panicum, Muhly, wild sedges, and Aster 'Miss Bessie' at the front of the bed.
I. virginica with Gulf Coast Penstemon in foreground and the hybrid musk rose Ballerina in far background