greene said:Plantrob, is there any way you can hold off digging up the tree to help get a more positive identification? There should be no danger of the plant spreading if you stop the growth before the tree fruits. 
I'm not concerned about the tree spreading - the birds do a good enough job spreading mulberries all around, one more source of fruit isn't going to make that big of a difference. But I've had a hard time digging up mulberry volunteers once they've gotten themselves established, so I don't want to let it go too long. I can usually identify mulberries easily, even at a young stage - this one is really quite different looking. I can hold off a little while to see how it develops later into the year.
