Charles Wolfe (in the book about the C.F. that accompanies the Bear Family set) says that "Sweet Fern was a song AP found in his collecting trips into the east Tennessee hills; more commonly known as Sweet Bird, it was written and copyrighted in 1876 by Thomas Westendorf and George Persley. It shows up in a number of southern folksonhg collections and had even been recorded the year before (1928) by WV singers Orville Reed and Richard Harold." Good guess, Ranger Steve!