I've got this plant all over my front slope. It's new this season, and hasn't bloomed (yet). I can't find a good match in any of my usual weed ID resources, or my native plant guides. But I'm starting to wonder whether it's first-year Joe Pye seedlings. I do have a fair amount of Joe Pye weed on the slope, which could certainly have reseeded. The stem is pretty sturdy, but not like a tree seedling. What do you think?