Cutting back peonies completely in August is generally not recommended. Peonies are perennial favorites, admired for their dramatic, lush blooms that appear in late spring and early summer. Although the flowers fade by mid-summer, the remaining green foliage is essential for preparing the plant for the following year. Removing the leaves prematurely in August is detrimental to the plant’s long-term health and next season’s flower production.
The Critical Role of Summer Foliage
The vibrant green leaves of your peony plant remain functional long after the petals drop, serving as the energy factory for the entire perennial. Throughout August, the foliage is actively engaged in photosynthesis, converting sunlight into carbohydrates, or sugars. These carbohydrates are transported and stored in the plant’s underground root system. This stored energy is the fuel source the peony relies on to survive winter dormancy and initiate the flowering process the following spring. Removing the foliage prematurely in August starves the plant, significantly depleting its energy reserves. Insufficient energy storage directly correlates with a reduced number of flowers and weaker stems in the next growing season. Furthermore, the plant is simultaneously setting the microscopic, over-wintering flower buds during this late summer period, a process that requires substantial resources from the foliage.
Corrective Trimming Versus Full Cutback
The timing and method for pruning peonies depend on the type of plant, usually either herbaceous or tree peony varieties. Herbaceous peonies, the most common type, die back completely to the ground each winter. They require a full cutback only once the foliage has naturally senesced and the energy transfer is complete. The proper timing for this complete cutback is in the late fall, typically after the first hard frost, when the leaves have turned yellow or brown, often around October or November.
Herbaceous Peony Trimming in August
In August, the only acceptable trimming for herbaceous peonies is deadheading. This means removing the spent flower heads just above the first set of true leaves. You may also selectively remove leaves that show clear signs of disease, such as powdery mildew or botrytis blight, to prevent the spread of fungal spores. When doing this, use clean tools and remove the affected material from the garden entirely, but do not remove more than a third of the overall foliage.
Tree Peony Care
Tree peonies develop permanent woody stems and should never be cut to the ground. They are treated differently and only require light shaping or the removal of dead wood, typically in early spring.
Essential Late Summer Peony Maintenance
Since a full cutback is off-limits in August, gardeners should focus on beneficial maintenance tasks that support the plant’s health and energy accumulation. Peonies are notably drought-tolerant once established, but deep watering is beneficial if your region experiences prolonged dry conditions. As a guideline, if the plant has not received about an inch of rain over a two-week period, a thorough soaking will support the energy storage process.
Sanitation is an important late-summer activity, especially given the plant’s susceptibility to fungal issues like botrytis blight. Clear any fallen debris or weeds from around the base of the plant to improve air circulation and reduce the humidity that allows spores to thrive. If your soil is poor, a light application of a low-nitrogen fertilizer after the blooming period can help replenish nutrients, but this is usually only necessary every few years for mature plants. Dividing or transplanting established peonies should be delayed until the early fall, around late September or October, when the plant has entered its dormant phase.