Our songs today are horticultural in nature.
Carol #8, "Lo, How a Rose E’er Blooming," was written in the late 16th century, and translated into English in 1894. It’s in the green Lutheran hymnal, if anyone still uses those (I love the green book). Here are the lyrics, once in the original German and three times in English (one literal translation and two poetic ones suitable for singing).
The reference to the rose comes from Isaiah 35:
The wilderness and the solitary place shall be glad for them; and the desert shall rejoice, and blossom as the rose. It shall blossom abundantly, and rejoice even with joy and singing: the glory of Lebanon shall be given unto it, the excellency of Carmel and Sharon; they shall see the glory of the LORD, and the excellency of our God.
Carol #9, The Holly and the Ivy, sounds pretty frankly pagan rather than Christian in its chorus, and at one time it probably was a pagan song. However, the version most people sing now has been Christianized, and it’s about the birth of Jesus.
It has a lovely tune. You can find some lyrics and alternate lyrics here. The first place I remember hearing this song was on the stage of the Guthrie during "A Christmas Carol." I believe Scrooge’s little sister Fan was singing it, in a crystal clear, lovely voice.
I found two versions of it I liked.
The other 12 Carols are here.