Conversation so far:
what is temps adept floridum?
The tune is that of "Tempus adest floridum" ("It is time for flowering").
what is special about the tune?
a 13th-century spring carol in 76 76 Doubled Trochaic metre first published in the Finnish song book Piae Cantiones in 1582.
was this song popular?
The tune has also been used for the Christmas hymn Mary Gently Laid Her Child, by Joseph S.
Cook (1859-1933.
Was it used for anything else?
in 1853, he and Helmore published twelve carols in Carols for Christmas-tide (with music from Piae Cantiones).

Question: did he work with anyone else?
Self-contained rewrite: did Joseph S. Cook work with anyone else other than Helmore?