Plant CSI Needed!

     These pictures show a half dozen very tall plants weeds that have grown in a large pot on my deck this year.
     I have no idea what they are.
     The plants weeds may have been volunteered by passing birds, or by passing black bears, for all I know.
     The same container had a variety of flowering plants in it the last two years, as shown in the other photo, so I figured that's what the plants weeds were. But so far no flowers, and now they're developing seedheads.
     Any ideas what they are? Anyone? Do i grab the roundup?