To give the full (2 verse) version that I quoted partially above.

LO, HOW A ROSE UPSPRINGING
Melody C15th Tr. by Theodore Baker

Lo, how a Rose upspringing on tender root has grown;
Known from the prophets' singing of Jesse's line the crown.
While shone the Star so bright,
It came a flow'r of winter in stillness of midnight.

Fair Rose in manger lowly Isaiah told of yore.
Our dear Redeemer holy the Blessed Mary bore;
This gift from God above
To bring us men salvation, lay shelter'd in her love.

Taken from "O Come Emmanuel" An Advent devotion for Choir and Congregation. Published by the Royal School of Church Music 1963
NP