Aren't they pretty?
Yes, they are naturalized. A few days from now there will huge patches of them on that side of the "park". These are just starting. We have this wonderful bike path which runs along the Saddle River through several towns with ponds on either end and one in-between, it is well loved and used, but most people stay on the path and don't venture into the wooded area around it. Last Spring I saw a lot of plants coming up a bit later, super garlicky, I think they are Ramps.
This fellow was painting the waterfall yesterday.