My ponds have several natives that would be hardy in your area, that may be of interest to you.

Iris versicolor (Harlequin Blue Flag)
Iris virginica (Virginia Iris)
Iris fulva (Copper Iris)
Iris pseudacorus (Pale Yellow Iris) Introduced, but a widespread species.
Orontium aquaticum (Golden Club)
Sagittaria sp. (Arrowhead)
Peltandra virginica (Green Arrow Arum)
Nymphaea odorata (American white waterlily)
Rb

Does wild rice work, and anyone know where it is available?

Got room for 100 plants? They are available in quantities of of 100 for $50 and are shipped out in late June. These are young wild rice plants. Do not ask me what that means as I have no idea. But you can contact Wildlife Nurseries in Oshkosh, WI Phone 920 231-3780 Fax 920 231-3554
I recommend getting their catalog as they are specialists in wild area restorations and carry mostly natives in quanitity. Please let them know that I, Jerry Copeland, recommended them to you. Nothing in it for me. Just want to remind them that I am still kicking around though I have not ordered anything from them in years. Definitely want to but too busy working on and in the house first and then ????

Sadly, I don't quite have enough room for 100 plants. :)

Razorback,
That's a great list...and I have most of them as marginals and the water lily. I love them all.

I did find that Hornwort or coontail (Ceratophyllum demersum)is a native floating plant and can usually be purchased. Water buttercup (Ranunculus aquatilis)is another native, but nearly impossible to buy.

I also got some great suggestions from the aquatic plant guy at the IN DNR. Just pasting his email below:

"For floating plants the best options would be spatterdock (Nuphar advena) (actually kind of emergent since the leaves don't float on the water's surface), white water lily (Nymphaea odorata), and watershield (Brasenia schreberi). Spatterdock and water lily can sometimes densely ring a pond although spatterdock has the greater tendency. Watershield is a cute little plant, but you generally only see it in the SE part of the state, I also don't think it is much used in trade. Most of the water lilies for sale are non-native species. Most of the spatterdock for sale is probably Nuphar lutea, a Eurasian species.
Most people do not look to plant submersed species since they are usually already present in most lakes and they usually show up pretty quickly after a pond is built. People typically are more interested in killing the submersed species than they are planting them. It are the water garden types of folks that get told that for their water gardens they need to put in an "oxygenator" plant. They then think that ponds need these same things. Probably the most common native submersed species in trade are coontail or hornwort (Ceratophyllum demersum) and native elodea (Elodea canadensis). Coontail can definitely become a major nuisance and sometimes elodea can as well. My main tip for those thinking they need to add submersed species is to wait. If conditions are suitable for submersed plant growth the plants will show up soon. If conditions are not good (turbid water, little shallow water, poor substrate), no matter how much planting, one will probably not get much growth. Unfortunately, invasive species tend to do well in the conditions that do not favor our natives."

My favorite marginal plant is Cardinal Flower. Unlike a lot of wetland/margin plants, Cardinal Flower (Lobelia cardinalis) grows well in the shade. It also flowers well in the shade and attracts hummingbirds. It is definitely the showiest flower of the whole bunch (OK, you could argue for Pickerelweed or water lilies). You should be able to buy it many places. It will spread by seed if you have some bare ground / mud available for it. It is quite small compared to many of these plants, and is great for a small pond. Cardinal flower grows fine in any moist to average soil, so you could have a clump near the pond that extends onto drier ground.