I'm willing to hazard an opinion that is is one of the variants of Amaranthus hybridus
. Unless those folks use abnormal cement blocks, it appears more like 6 - 7 feet tall rather than 9, which would fit this species.
here is the link to the FNA treatment: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200006982
Not surprisingly, FNA describes this as a complex species in need of further work.