Paul, Iris pseudacorus has a strong midrib or will be noticeably thicker thru the center of the leave. Louisiana iris do not have a noticeable midrib. To tell a water iris from a bearded iris cut a leaf and hold it up to a bright light. You will see what are called 'watermarks'. It almost looks like you can see cell divisions, I like to describe it as looking like a DNA fingerprint. Bearded iris never have this 'watermark'. I think all water iris show a 'watermark' to varying degrees.