Beautiful pictures! I grew up in the back country roads of WI and these trees are abundant. We used to call them Sumac trees and growing up we would make forts out of them. Similar to the way they make their shelters on 'Survivor'. Your pictures bring back memories.
I wouldn't call them weeds. Lots of wildlife, especially the birds, use them as shelter. We would find deer beds below the trees. These can grow 15-18 ft tall.