Gymnocladus dioicus

Many years ago, a friend of mine tried to create an arboretum on his property.  With enthusiasm he bought 800 whip seedlings from the DNR and set out to plant them around his property.  He selected good trees, but he ran out of steam after planting about 700 and gave me the remainder.  It was late in the year, too late to plant them out, so I heeled them in out by the Dawn Redwoods, in a huge pile of mulch.
By the time spring rolled around again, all of my friends trees had succumbed to the lawn mower. But my trees were still kicking.  Some of those trees never left the site of the mulch pile, and now are competing for space with M. glyptostroboides.  But I planted out half a dozen of the Kentucky Coffee Trees.  Most have grown 2 feet per year to 30-35 feet, only one has flowered (sparsely, last year), and they are grand specimens.

But one little tree insists on doing her own thing.

This tree I'm estimating at 14 feet, less than half the growth rate of the others. The other thing that is special about her is that she has bloomed.  Not just a little, but a lot, and for years.

I have no idea whether we have anything special here or not.  I found one picture on flickr of a dwarf Kentucky Coffee Tree at the Minnesota Arboretum, but the shape of that tree is nothing like mine. I've emailed a horticulturist friend to see if he can help.