Pat:
Pickerelweed is a marginal, growing both in and out of the pond at the waters edge. I like American Pondweed. It provides some shade for the fish, it's easy to fish in with weedless topwater lures and it's easy to control if it gets out of hand.
The downside is that it doesn't provide cover for YOY fish. That's not a problem if you have artificial cover in the pond for them. Look at Eel grass too.