More photos of Prunus americana ..
http://www.cas.vanderbilt.edu/...
http://www.nrem.iastate.edu/cl...
Can you be sure the Prairie Moon nursery has the correct photo? Many don't, educational sites are the best to look for accuracy, but the photo shows leaves with flowers as you state Chelle, Ginger's tree has flowers without leaves.
Missouri Botanical Garden shows it with a few leaves .. and the leaves look broad.
http://www.missouribotanicalga...
Leaves also look broad on this drawing ..
http://www.holoweb.com/cannon/...
It's not easy to say which it is, fruits would help. Leaves need to fully develop also, but they can often vary a little.
