This pretty plant grows in our Amphibian Pond. It is known by the common name of water willow, for very obvious reasons. It is a native plant that can become densely abundant in some situations. We have no idea how it arrived at the pond, as we didn't plant it. But it has been around for about 8 years now. It is certainly spreading, but not as fast as I thought it was going to. Nonetheless, we have a good stand of it right now.