Winter Heaving of Peony Roots

Winter can be trying on peonies, particularly for the newly planted, less-than-ideally sited or poorly mulched. Flower buds can withstand sub-zero temperatures, but the continued freezing and thawing of more mild winters can result in what is known as heaving. This term refers to the resulting force of a layer of ice forming beneath the surface of the soil. The expansion of this ice pushes a layer of soil upwards. The cumulative effects of this process can be quite pronounced, particularly after a winter like the one we experienced this year with many periods of freezing and thawing. Its frost heaving which is responsible for delivering us a fresh crop of ‘Connecticut potatoes’ each spring, as rocks come up to the surface. So as you begin your spring clean up, inspect your peonies for signs of heaving.

Peony roots that are not firmly set in the ground or which are in wetter soils are particularly susceptible. This poor plant is in both wet soil and did not have its roots insulated by a layer of mulch. Mulch insulates the soil and can help to prevent heaving. Roots like these, exposed by frost heaving will not survive and will severally weaken a plant.

Exposed roots can desiccate, which can be deadly for young tree and herbaceous peonies, and all plants.

The best solution is to generously mound soil around the exposed roots and tamp it down firmly, but gently with your foot. Do this now in the early spring before any exposed roots wither.