I recently checked out the "Wild Medicine" exhibit going on at the Bronx Botanical Garden. It was truly gorgeous and fascinating. Plants that have medicinal uses were arranged in separate habitats, with winding paths and placards to accommodate and educate visitors. There was a tropical rainforest habitat, a replica of a Renaissance era "botanical garden", and, of course, a desert area which features fabulous succulents.
I highly recommend checking it out if you are in the New York area, I spent the entire day exploring the grounds and the library, and still didn't see everything.