Peonies are easy-to-grow, long-lived, and reliable performers in the garden. But they occasionally have issues. The most common issues with peonies are listed below.
Peonies are prized for their flowers so when they are not blooming, it can be disappointing. There are several possible causes for failure to bloom.
Learn about the reasons peonies fail to bloom in this article: Reasons Why Peonies Fail to Bloom.
Powdery mildew is a common problem later in the growing season, especially on plants growing in too much shade with poor air circulation. The powdery mildew fungus (Erysiphe) covers the leaves in what looks like a dusting of white powder. Once this disease appears on the leaves, there is little that a gardener can do. Fortunately, this foliar disease does not typically kill peony plants. In the fall, remove the diseased leaves and discard them to prevent re-infection next year. Diseased leaves should not be composted.
Peony leaf blotch (Cladosporium) causes irregular brownish-purple spots that appear on peony leaves in summer. The disease is favored by warm, humid weather. Providing good air circulation and avoiding wetting the leaves when watering can help reduce disease severity. Fortunately, this foliar disease does not typically kill peony plants. In the fall, remove the diseased leaves and discard them to prevent re-infection next year. Diseased leaves should not be composted.
Botrytis blight is a common fungal disease of peonies. The fungus Botrytis paeoniae attacks stems, leaves, and flower buds. It is most common in cool, rainy weather.
Young shoots attacked by botrytis blight discolor at the base, wilt, and fall over. Affected flower buds turn brown and fail to open. The withered buds are later covered with a mass of gray, fuzzy fungal spores. Infected leaves develop large, irregularly shaped dark brown spots.
Botrytis fungi survive in debris left in the garden over winter. In spring, remove withered flower buds and spent flowers. In fall, cut off the peony stalks at ground level. Remove the plant debris from the garden and destroy it. If the peonies are growing in partial shade, move the plants to a sunnier location.
Cool, wet conditions during the spring favor the development of Phytophthora blight on peony. The fungus Phytophthora, common in most soils, initially attacks either the roots or the developing shoots at the soil level, causing a blackening and decay of stem tissue. These black, often sunken areas, usually several inches long, may also appear on upper stem tissue. Stems tend to fall over at the stem lesions. Flowers, buds, and leaves may also turn a dark brown or black color. The tissue will appear somewhat leathery.
The disease is most serious in soils that are poorly drained. The disease can be spread by splashing rain or contaminated tools, soil, or plant material.
To prevent Phytophthora blight, plant peony in well-drained soils and thin crowded plantings. If disease symptoms appear, destroy infected plant parts. Peony plants with rotted roots need to be removed together with the adjacent soil. Fungicides may help control the disease when the roots are not rotted. Spray the foliage, bases of shoots, and nearby soil at intervals of 7 to 10 days during rainy periods with a fungicide containing mancozeb or maneb.
Ants on blooms are not a problem. They are also not necessary for peonies to flower. The ants are attracted to the sugary nectar produced by the peony buds. The nectar is a good food source for the ants. Peony buds will open without the presence of ants.
Many peony flowers have double or triple the number of petals – making them too heavy for their stems to support. Therefore, staking the peony stems as they emerge in the spring or as the flower buds form will provide the extra support needed to keep the blooms upright.
- Growing Peonies in Iowa
- Growing Garden Peonies (pdf)
- Transplanting and Dividing Peonies
- Getting Peonies to Bloom (video)
- Gardening in the Zone: Peonies (video)
- Peony Types and Cultivars for Iowa
- Reasons Why Peonies Fail to Bloom