My researches seem to indicate that Buttercup Joe was written by Daniel Moore: The Era (May 12, 1872) carried an Advert for "Daniel Moore, renowned coloured humorist, legitimate instrumentalist and star dancer in conjunction with GREAT LITTLE FRENCH.… [Moore is ] author and composer of "Hot Peas" "The Brave Militia Boy" [and] "Buttercup Joe"…
more at http://folksongandmusichall.com/index.php/buttercup-joe/