I have posted about my 'Sweet Flag' a couple of times. It grows in my stream and the sides of my pond. It may be divided into tons of plants. I got a pot of it at a pond store originally. The pot was sitting in several inches of water at the time but it does fine in just damp conditions. I am not sure how well it would handle CT conditions. I am in North Carolina. We got down to 7 degree F a couple days this year (unusually low for us) and certainly the pond/stream plants are doing well and the land plantings are not dead; and not always being damp, don't do that well anyway.

Sweet Flag is a clumping long narrow leaved plant about a foot high.

Thank you! I looked up images of it on Google and I think I have some of that back there. I had a few plants like that shoot up from around the pool and they did last even after the pool dried up. I guess it might look nice if I planted a whole bunch back there... that's a lot of work. Are there any other plants you'd suggest, like anything that would spread out on its own?

I don't have any experience with spreading aquatic plants but I suspect others will have a few ideas. But back to sweet flag for a moment. The hardest problem with it is digging a big clump up. It becomes large and well dug in. However, in a muddy environment I would think it would come up without too much trouble. From that point, it is easy to soak it in a puddle and then yank perhaps a hundred plants apart in a few minutes. At that point, you could take another minute to sling hand-fulls of plants into all shallow directions and you are done. No rooting necessary; in shallow water, the plants will take care of that.