He helped one in time of trouble, making an enemy of another faction, and was saved from the fate of dying as other mortals, by being turned into a plant. The very same plant Paeon had used to heal the first god. Seems to me that the god who Paeon had healed was a bit short in the thank you department. Legend and superstition have always been close to the Peony. Before Pluto and Mars were healed by Paeon, using the Peony root to cure their wounds during the Trojan wars, legends spoke of the powers of the Peony.
Powerful forces reside in the blossom of a plant that glows in the dark on the night of a full moon.
Seeds from certain Peonies emanate a pale light in the darkness. To contain that magic, the roots could only be dug during the night. If one were to disturb a Peony during daylight hours, Woodpeckers would appear and proceed to peck your eyes out. Somewhere around 77 AD, Pliny's Natural History gives the first known detailed description of both the plant and it's seeds. Twenty known illnesses were cured by part of the plant.