I grow Japanese Iris in pots which can be partially submerged up to soil level. They come in many colors. When dormant you may want to remove them from your pond if it freezes solid. The iris themselves are perfectly hardy.

I have grown Louisiana Iris Black Gamecock for 20 yrs in my little pond, I did not have to remove it for the winter, So I assume Louisiana Iris would be hardy in a freeze zone pond.

Will keep my eye out for one!!! Nice flower