Saint Ambrose (339-397), Bishop of Milan, concurs with this image, writing: “The root is the household of the Jews, the rod is Mary, the Flower of Mary is Christ. She is rightly called a rod, for she is of royal lineage, of the house and family of David. Her flower is Christ, Who destroyed the stench of worldly pollution and poured out the fragrance of eternal life. As He Himself said. ‘l am a flower of the plain, a lily of the valleys'” (Song 2:1).
The Life of the Virgin Mary, the Theotokos, Holy Apostles Convent, Colorado, USA, 1989, pp. 157-158