I agree with RossC that all of these may spread and will need attention paid to unwanted volunteers. In our pond, Pickerel and N. Odorata are prolific seeders and we see seedlings all around the perimeter. It depends on the look you want. To me, pickerel may look a bit more unkept than the iris but flowers all summer, while Iris looks a bit more kept, blooms in the spring, and provides nice foliage all summer. Also, pickerel is emergent will grow in water 12” deep water while the iris can grow above the waterline down to about 4” deep.
For plants that spread by root or rhizome, planting in pots or planting rings can work to prevent spreading. I have both with pickerel and white lilies dotting the whole perimeter but I think I am aiming for a more wild look.
