Try contacting George Ayers at Michigan State University, Dept. of
Entomology, East Lansing, Michigan 48824-1115.  He has done a
significant amount of research on bee forage and most likely would be
very interested in a tree that blooms in August and is attractive to
honey bees.  He had an article in the American Bee Journal about two
years ago that discussed late blooming (for North America) trees.  One
was a linden tree of asian origin.  I can't recall the other tree.  I
would be interested in learning more about your tree.