Yard and Garden: Growing Garden Peonies

peony flower

The garden peony is a popular, long-lived perennial that provides abundant flowers in spring and attractive foliage throughout the growing season. If given a good site and proper care, an established peony will flower for many years. Plantings as old as 100 years have been recorded. To have additional questions answered, contact horticulturists at the Iowa State University Hortline by calling 515-294-3108 or emailing hortline@iastate.edu.
Are ants necessary for peonies to flower?
Ants aren’t 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.  
My peonies bloom poorly. What could be wrong?  
Several factors may cause peonies to bloom poorly.  
Peonies perform best in areas that receive at least six hours of direct sun each day. Peonies that receive less than four hours of direct sun will bloom poorly. Plants growing in a shady location should be transplanted to a sunny site in mid- to late September.  
Peonies planted too deeply often fail to bloom well. When planting peonies, position the peony buds 1 to 2 inches below the soil surface. Peonies that are planted too deeply produce lush foliage, but don’t bloom well.  
Recently planted or divided peonies may not bloom well for two or three years. The new plants need to grow stronger before they are capable of blooming well.  
Also, premature removal of peony foliage in July or August weakens plants, resulting in few flowers the following spring.  
Some of the flower buds on my peonies don’t open. Why?  
There are several possible explanations as to why peony buds fail to open.  
Peonies bloom best in full sun. In partial shade, plants are weak and may not be able to supply adequate food to the developing buds. As a result, the undernourished buds don’t develop fully. Peonies growing in partial shade should be transplanted to a sunny site in mid- to late September.  
Fungal diseases, such as Botrytis blight, may infect peony buds. Infected buds turn brownish black and wither. Cool, wet weather in spring favors the development of fungal diseases. Sanitation is the most effective means of controlling Botrytis blight and other peony diseases. Cut off peony foliage at ground level in fall. Remove the diseased plant debris from the area and destroy it.  
The flower buds may have been damaged by a late freeze. While the plants themselves can tolerate a light freeze, the buds are more susceptible to cold injury. Unfortunately, little can be done to avoid this problem.  

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