Mu Dan Pi (Mountain Peony Bark, Tree Peony Root Bark); Paeonia suffruticosa; Moutan Cortex Composed of the cortex, or root bark of the tree, the Mountain Peony is spicy and bitter, with cool energetic properties. As such, it is classified as an herb that cools the Blood. While the cooling energy of Mountain Peony clears heat, cools blood, and reduces swelling, it also has a mild ability to invigorate blood circulation. Properties Bitter, acrid, cool Channels Entered Heart, Liver, Kidney