This is a really tough one. I incorrectly ID'd it at first, until I spoke with the former manager of Roger Williams Park, who gave me the correct ID. Good luck.
How the f did you guess that? Wow, nice job!!! I thought it was S. giganteum at first, but fortunately I ran into the man who planted the tree the same night, and he gave me the correct ID. Which is pretty incredibly coincidental, actually.