PlantLife Online

Answer

There are a few common reasons peonies don't bloom; they lack of sun, competition, warm winters and being planted too deep. Peonies need a good 8 hours of full-sun for their best bloom, it could be possible a tree or shrub has grown to block the sun your peony once had. Peonies like their space, over crowding can cause competition for water, nutrients and light. Competition from other garden plants maybe obvious on the surface but root competition from neighboring trees and shrubs is common and hard to determine. Since your peony has bloomed in the past, planting depth and cold requirements are most likely the cause of your lack of flowers, however peonies require winter temperates to dip for a few months each year to produce flowers, planting too deep can also cause them not to flower.

If the environmental facts we just discussed do not seem fit there are a few pathogens that are known to cause stunted growth in peonies. Meloidogyne, Rotylenchus and Fusarium just to name a few, all of which the recommended course of action is removal. It is recommended that infected peonies be removed from the garden and not replanted in the same area for one year. Some symptoms to look for in addition to the stunted growth are yellowing, wilting, ring spot on the leaves and galls developing on the roots.

Hope this helps!

Happy Gardening,
Plant Life Online