From the perspective of the Paeonia lactiflora plant, the approach of winter is not a threat but a necessary, genetically programmed phase in its annual life cycle. As daylight hours shorten and temperatures drop, the plant receives environmental signals that trigger a physiological shift from active growth to dormancy. This process, known as acclimation, is crucial for survival. The plant begins to transport energy—in the form of carbohydrates and other compounds—downwards from the fading foliage into its storage organs: the thick, fleshy roots and the "eyes" or buds at the base of the stems. These eyes are the meristematic tissue that will generate next spring's growth. The plant's goal is to conserve all possible resources underground, where they are insulated from the freezing air above.
After the first hard frost, you will observe the foliage of Paeonia lactiflora turning yellow and then brown. This is a deliberate and beneficial process from the plant's point of view. It is not dying but engaging in nutrient resorption. The green chlorophyll breaks down, and the plant systematically reclaims valuable nutrients like nitrogen and phosphorus from the leaves, pulling them back into the root system for storage. It is critical that you do not remove the foliage while it is still green or yellow, as this would interrupt this vital nutrient recycling system, effectively robbing the plant of the energy it needs to fuel spring blooms. Allow the leaves to remain until they are completely brown and withered.
Once the foliage has fully died back, it is safe and advisable to cut the stems down to within 2-3 inches of the soil level. From the plant's perspective, this serves two key purposes. First, it removes dead material that could harbor fungal spores or pest eggs over the winter, reducing the risk of disease when the plant breaks dormancy. Second, by eliminating the tall stems, you prevent wind from catching them and potentially rocking the plant, which can damage the delicate roots and eyes just below the soil surface. A clean cut also helps the plant seal off the wound, preventing moisture from entering the hollow stems and causing rot in the crown.
While Paeonia lactiflora is exceptionally cold-hardy, its most vulnerable parts are the buds or "eyes" located just at or below the soil surface. In its natural habitat, a layer of fallen leaves would provide a protective blanket. In the garden, we replicate this by applying a loose, airy layer of mulch, such as straw, shredded bark, or pine boughs, after the ground has frozen. The timing is critical. Applying mulch too early can trap warmth and moisture, encouraging rot and confusing the plant's dormancy cycle. Once the soil is frozen, the mulch acts as an insulator, maintaining a consistently cold temperature and preventing the damaging cycle of freeze-thaw-freeze that can heave the plant's crown out of the ground, exposing the eyes to desiccation and cold injury.
The extensive root system of Paeonia lactiflora is its anchor and larder. While the plant requires consistent moisture during the growing season, its winter needs are different. The goal is for the roots to enter winter in a moderately moist, but not waterlogged, state. Saturated soil can freeze solid and damage root tissues, or lead to anaerobic conditions that cause root rot. Therefore, it is important to ensure good drainage. If autumn is particularly dry, providing one deep watering after cutting back the stems and before the ground freezes is beneficial. This gives the roots a final reserve of moisture to sustain them through the winter, as frozen soil makes water uptake impossible.
