Boxelder Tree, Acer negundo HTH Chris

extremely poisonous.. in every aspect ..... the leaves.. the roots.. the berries... etc.. if you have kids that stick things in there mouths.. get rid of it ASAP ... spanish women used to rub some version of it in their eyes.. bella donna ... ken ps: and even if you dont have kids.. the birds will plant a million of them for you ... if you do let it go to seed.... pps: part of the potato family.. and it always amazes me.. that all of the potato is also poisonous .. but for the spud.. whats that all about ... who was the first guy.. to work his way down all that poison parts ..... to get to the edible part.. 8 inches underground.. i suspect.. it was a number of dudes in the same family ... and son #4 ended up inheriting..l ol...

Thank you, both! So, is this something I want to keep, or yank out ASAP?

If you'll look closely, there is a stem that rises above the leaves that has been bitten or cut off. It's a vine. Possibly sweet autumn clematis, Clematis paniculata.