I'm not sure, but in your whole-plant photo, it looks like there's a stem on the left with somewhat 'shreddy' bark? Have a look at the last photo at this link, and see if you recall seeing bark that looked like that?
http://www.namethatplant.net/p...
It's a handsome plant for a handsome banner, and BONAP says
P. opulifolius might be found growing wild in Ann Arbor area.
http://bonap.net/MapGallery/Co...
PS Thanks for the acorn!
