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. virginica with Gulf Coast Penstemon in foreground and the hybrid musk rose Ballerina in far background