I was waiting for someone more knowledgeable to answer you. YOu might look around the perennials, shrubs, and aquatic forums - people know a lot! I also know I wasn't sure about what to answer, because I wasn't sure of your site conditions - like what kind of soil, sun, and how long the water stands or how quickly it drains, and so on. I'm sure if you give more details on a forum that's more frequented, you will get a lot of helpful information.

Best of luck!