Common Disease Problems
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Root Rots: A number of pathogens cause root rots. The symptoms are wilting and dying of the plant and rotted roots when the plant is dug up. Burpee Recommends: Pull up and discard infected plants. Make sure your soil has excellent drainage.
Virus Diseases: These can cause ring spots, leaf curls, general dwarfing of the plant and mottled leaves. The disease can be spread by insects such as aphids and leafhoppers, and hands and tools. Burpee Recommends: Remove and destroy affected plants. Sterilize tools you used when working with affected plants before reusing them.
White Mold: Also called crown rot or Southern blight, this fungus causes deterioration and rotting at the crown causing the leaves to turn yellow, collapse and die. There are water soaked lesions on the stem near the soil line. In high humidity, coarse cottony webbing develops over the stem base and surrounding soil. White to tan fruiting bodies resembling mustard seeds appear at the base of the plant. Burpee Recommends: Remove and discard affected plants. Consult your local Cooperative Extension Service.
Common Pest and Cultural Problems
Ants: These are very common on peonies, but they do not eat the plant or cause any damage. They are attracted to the sugary droplets that form on the outside of the flower buds. They may also be attracted to the honeydew left by scale. Burpee Recommends: The ants are harmless, do not use insecticides. Check for ants before bringing in cut flowers.
Bulb Mites: These pests feed on peony plant roots, particularly on diseased or rotting areas. They are 1/32 inch long and white to brown. They can cause the foliage to emerge twisted as the buds were injured by the mites before emerging. Burpee Recommends: Inspect your roots before planting. Contact your local Cooperative Extension Service.
Japanese Beetles Japanese Beetles: Burpee Recommends: Hand pick early in the morning into a bucket of soapy water.
Scale: Small bugs look like brown, black, gray to white bumps on the stems of plants. Scale may not have any apparent legs and may not move. Scales have a sucking mouth part. Scale may produce honeydew so leaves and stems may be sticky. Scale can weaken the plant causing it to grow very slowly and may wilt at the middle of the day. Burpee Recommends: Completely spray the stems with Insecticidal soap. For a severe infestation contact your local County Extension Service for recommendation for your area.
Thrips: Thrips are tiny needle-thin insects that are black or straw colored. They suck the juices of plants and attack flower petals, leaves and stems. The plant will have a stippling, discolored flecking or silvering of the leaf surface. Thrips can spread many diseases from plant to plant. Burpee Recommends: Many thrips may be repelled by sheets of aluminum foil spread between rows of plants. Remove weeds from the bed and remove debris from the bed after frost. Check with your Cooperative Extension Service for pest controls.
Why did my peony develop a flower bud that never opened? This condition is called “bud blast” and will occur when the plant is stressed at the time of bloom. The stress can come from a variety of causes including too little water, too much shade, poor soil, or too cool temperatures when buds are developing. If it occurs every year you should probably move the plant to more favorable conditions in the fall.
Can I grow peonies in containers? Peonies do not tend to bloom well in containers. They are prone to bud blast because they are more stressed in containers than in the ground. Containers heat up faster and dry out faster than the ground. Also, plants use up nutrients more quickly in containers.
Can I grow peonies in Southern California? Unfortunately peonies require a cold winter in order to grow and bloom, they will not survive in southern California or any place warmer than zone 8. They are ideal for cold northern areas, however!
Why does my peony always attract ants? Is there something wrong? I have heard they are needed to open the flower buds. Ants are attracted to the sticky honeydew left from scale or other sucking insects, and the bud itself exudes a sticky substance that attracts ants. They are not needed for the flowers to open. Do not use pesticides to treat them, they do no harm and the pesticides are more likely to do harm in your garden than good. Just wash them off with a hose, and check before you bring cut flowers inside.
I want to move my peonies, when should I do that? Dig up and divide peonies in fall after the foliage dies back. Do not move them often, they are long lived plants and unlike many other perennials they do not need to be divided every few years in order to bloom well.