dirca palustris, eastern leatherwood.

For sure. Have you tried propagating Dirca?

Reportedly a difficult plant to propagate. I thought for sure Sam would've tried his/her hand at it, but apparently not.

In spring along the Potomac River C&O canal I found these interesting understory flowering shrubs -- I know what they are:

hi beng12, looks like bladdernut aka Staphylea trifolia

about Leatherwood Bill Cullina writes ...a refined plant for the woodland garden but lacks the "container appeal" so important in our modern day cash-and-carry nursery business, and I imagine this partially explains its scarcity in the trade.

Here it is today in Maryland.