Myths, Symbols & Folklore
peony: "In China it is a symbol of wealth and honor. It was regarded in antiquity as protection against the wiles of satyrs and fauns. In the Middle Ages it was often used as a medicinal and magical plant; the seed of the peony served as an amulet. As the 'rose without thorns,' it is a common symbol of Mary in medieval paintings." (Herder)

But really. Isn't *everything* a symbol of Mary in medieval paintings? :)