I started this tree from seed i collected last fall. The tree was growing at waters edge in zone 7 in Maryland. About 20' tall. Rough bark. I remember seeing white flowers but have no pic. Here is the tree i started and seed pods.
Cephalanthus occidentalis? http://www.google.co.uk/search?q=ce...w&biw=1280&bih=647&sei=Z1CAT4XBDKGu0QWur-SWBw