Peonies, admired for their abundant blooms and rich foliage, are a cherished addition to many gardens. Proper winterization protects these plants from harsh conditions, helping them store energy for robust growth and prolific flowering. This preparation varies by peony type, but the goal remains consistent: to safeguard the plant and encourage future blossoms.
Why and When to Winterize Peonies
Winterizing peonies offers several benefits, primarily shielding them from severe weather conditions like extreme cold, drying winds, and heavy snow. This practice helps prevent damage to the plant’s structure and root system. It also plays a role in disease prevention by removing potential overwintering sites for pathogens, which can otherwise re-emerge in spring and affect new growth. By preparing peonies for dormancy, gardeners promote stronger plants and more abundant blooms.
The optimal time for winterization is typically in the fall, after the first hard frost has occurred. At this point, the peony foliage naturally begins to die back, turning yellow or brown. Waiting until this natural dieback ensures the plant has absorbed all possible energy from its leaves, which is then stored in its roots for the winter.
Winterizing Herbaceous Peonies
Winterizing herbaceous peonies involves cutting back the foliage. Once the leaves have turned yellow or brown, typically after the first hard frost, use sterilized pruning shears to cut the stems back to about 1 to 3 inches above the soil line. This action is important for disease prevention, as fungal spores like botrytis blight or powdery mildew can overwinter on dead foliage and infect new growth in the spring.
After cutting, it is important to promptly remove and dispose of all cut foliage and debris from around the plant. This material should not be composted in a home compost pile, as the temperatures are usually not high enough to kill lingering disease spores, which could then spread back into the garden. Proper disposal helps maintain a clean growing environment and reduces the risk of future infections.
While established herbaceous peonies generally do not require mulching for insulation, newly planted or young plants can benefit from a light layer. Apply about 2 to 4 inches of organic mulch, such as straw, pine needles, or shredded bark, over the plant crown after the ground has frozen. This layer helps prevent soil heaving caused by freeze-thaw cycles, which can expose roots. It is important to remove this mulch in early spring before new growth emerges, as leaving it can interfere with proper growth and potentially lead to rot or reduced flowering.
Winterizing Tree Peonies
Winterizing tree peonies differs from herbaceous varieties due to their woody structure. Unlike herbaceous peonies, tree peonies should not be cut back to the ground, as they flower on old wood and their stems remain above ground throughout winter. Pruning should generally be limited to removing dead or damaged wood, or for shaping, typically done in spring after blooming.
A key consideration for tree peonies, especially those grafted onto herbaceous rootstock, is protecting the graft union from extreme cold. This union, often visible as a swollen area at the base of the stem, should ideally be planted several inches below the soil surface to encourage the tree peony to develop its own roots and offer natural protection. In colder climates, or for newly planted specimens, additional protection can be beneficial. Mulching around the base with a 3 to 4-inch layer of organic material like pine needles, straw, or shredded bark helps insulate the roots and maintain soil temperature. Ensure the mulch is kept a few inches away from the woody stems to prevent moisture buildup and potential rot.
For regions with very harsh winters or significant drying winds, wrapping the woody stems with burlap can offer further protection. Create a cage around the plant using stakes and then drape burlap loosely over the framework, ensuring good air circulation. This barrier shields the stems from sunscald and desiccation, which can occur when winter sun warms the bark during the day and temperatures drop sharply at night. Remove the burlap in early spring once the threat of severe cold has passed.
Common Mistakes and Tips for Success
Avoid common pitfalls during winterization. One frequent mistake is cutting back herbaceous peonies too early in the fall; the foliage needs to remain on the plant until it naturally dies back to store energy for the following year’s blooms. Another error is improper disposal of diseased foliage; always discard it in the trash rather than composting to prevent the spread of fungal spores.
Good drainage is important for peonies year-round, as they are susceptible to root rot in waterlogged soil. If your garden has heavy clay soil, amending it with organic matter can improve drainage. Peonies generally do not require heavy feeding, particularly with high-nitrogen fertilizers, which can promote lush foliage at the expense of flowers and increase susceptibility to disease. If fertilization is needed, a balanced or bulb-specific fertilizer applied after blooming or in late summer is often sufficient, ensuring it is applied around the drip line and not directly on the crown.
Throughout winter, monitor plants, especially those in containers, to ensure the soil does not become completely dry, though watering needs are minimal. As spring approaches, gradually remove any protective coverings or heavy mulch layers to allow the soil to warm and new growth to emerge unhindered. A clean garden bed, free of old debris, prepares the ground for the emergence of new shoots and a vibrant blooming season.