Common peonies (Paeonia hybrids) are a wonderful addition to any garden, known for their large and often fragrant flowers available in a variety of colors. Often referred to as the “King of Flowers,” peonies have been a status symbol since they were domesticated in China for medicinal purposes over 2,000 years ago. If you wish to grow peonies successfully, it’s important to avoid common pruning mistakes while caring for these herbaceous perennials. There are different pruning methods to consider depending on the season.
During the spring and summer growing season, focus on light maintenance pruning. This involves deadheading, or removing older, spent flowers; disbudding, or removing younger buds that detract from the growth of main buds; and thinning, which increases space between dense stems. Thinning helps shape the plant and improves light and air circulation, but avoid removing more than ⅓ of the stems at a time when your peonies reach about a quarter of their mature size. It’s essential for peonies to retain enough foliage to grow and store energy for blooming. As the growing season concludes and plants begin to die back due to freezing temperatures, typically around October or November, more serious pruning is necessary.
Trim plants near ground level to a height of about one or two inches, taking care not to damage the crown, which is located at or below soil level in the center of the plant. Damaging the crown can hinder the plant’s ability to produce flower buds for the next spring. Peonies are tubers, and you can divide a section of the crown with a few premature buds and attached tubers to propagate more plants (though recently divided sections may not bloom immediately). Avoid planting your herbaceous peonies too deep; going more than an inch or two beneath the surface may result in foliage but no blooms.
How to properly prune diseased peonies
Peonies may become infested with pests or contract various diseases requiring you to prune portions or entire plants during the growing season. Issues include bacterial blight, powdery mildew covering foliage, or root rot stunting growth due to lack of oxygen (often from overwatering). Be cautious of diseases that make it unwise to replant peonies in the same area, such as Verticillium wilt, which occurs without visible crown damage, or white mold causing stem discoloration and rot.
When pruning diseased plants, a common mistake is not properly sanitizing your shears with alcohol, bleach, or household disinfectants between cuts, potentially spreading the infection. Mistakes can also occur when disposing of diseased peony debris. While it’s possible to kill diseased material and nuisances like weed seeds in a composter reaching at least 148 degrees Fahrenheit, generally avoid adding diseased material to your backyard compost pile.
Fungi or bacteria that survive might spread, so it’s best to find alternative disposal methods for your peony trimmings. With ample garden space, you can bury the debris far away to naturally decay for a year, then rotate in a different plant type. In most cases, bagging and discarding diseased pieces is the safest approach.
Additional practices for growing and pruning beautiful peonies
To grow strong peonies, provide them with the best start. While there are multiple peony varieties affecting specifics, common herbaceous garden peonies thrive best in mountainous regions within USDA Hardiness Zones 3 to 8. They flourish in partial shade to full sun (requiring at least two hours of direct sunlight daily) and should be planted in acidic soil rich in organic matter with good drainage. September is the optimal month to plant or transplant peonies, ideally using fertilizer with phosphorus-rich materials like bonemeal to correct soil acidity imbalances.
A single peony plant can brighten your garden for decades with proper care, including using the right pruning techniques with tools like bypass pruning shears (such as this Fiskars pair available on Amazon) for cleanly trimming thick stems. Unless you detect disease signs in your garden, don’t hesitate to leave dead plant tops over winter. Perennial flowers like peonies offer food for birds and shelter for insects during cold weather, so maintaining a natural landscape in winter can benefit the local ecosystem.
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