Iris tridentata

If you are interested in extending your iris bloom season, Iris tridentata may be what you are looking for.  It is a beardless species iris native to wetlands from Florida to North Carolina.  According to Marty Schafer and Jan Sacks at Joe Pye Weed's Gardens, it grows in a wide variety of soil conditions.  My plant is growing in pine bark mulch at the edge of a bog garden.  If you observe the flower closely, you will notice that it lacks standards.  Unlike the iris you grow, this one spreads in all directions with long rhizomes and does not form a clump.  It is just starting to bloom.