One very well-known 19th century song on the theme was "Won't You Buy My Pretty Flowers?" - look on the EFDSS's Folkopedia for the details.

A few years after Ochs's song, the Moonies moved in on the flower-selling business. They were plaguing restaurants in Pittsburgh when I was there in the mid-1970s and the Pittsburgh photo collection Azizi linked to recently shows a guy selling what looks very like the same sort of flowers as they did, presumably very recently. They must have driven local poor people who were doing it even deeper into destitution.