At the Brooklyn Botanic Garden.
But if you are in the mood for the aquatic flowers' interesting, edible rhizomes (or for pork buns, for that matter), you need to visit Chinatown. The seeds are edible too - I've seen recipes for their use ranging from soup [the link, Kitchen Tigress is worth a visit] to snacks, where they are puffed, like rice. They sound about as easy to handle as hominy (some of you may recall the epic, multi-day pozole I made, once, with heirloom, artist-grown Indian hominy): much soaking and cleaning.
The seed heads. Good design for shower heads.