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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Peonies

This article was published originally on 5/10/2002

If you're looking for a long-lived perennial for the garden, the peony is just the plant. Peonies, once established, will flower for years if not disturbed. Peonies are sometimes called the Memorial Day flower because they are often in bloom during the late May holiday. Peonies general prefer full sun, adequate water, and a well-drained soil. After flowering, remove the spent blooms from the plant. This focuses more energy into other areas of the plant.

Garden peonies are classified into five different flower forms: single, semi-double, Japanese, and anemone. Single flowered peonies have one row of petals surrounding a cluster of yellow stamens. The stamens are the "male" reproductive organs of the flower and are composed of the filament and pollen-bearing anthers. Semi-doubles have multiple rows of petals surrounding a cluster of yellow stamens. The stamens of the double-flowered peonies do not bear pollen and have been transformed into petal-like structures. Japanese peonies have five or more large petals surrounding stamens that bear no pollen. The absence of pollen distinguishes the Japanese from the single flower form. Anemones are similar to the Japanese type except the stamens are wider and more petal-like. In addition to the five flower forms, the garden peony has two close relatives. They are the tree peony (Paeonia suffruticosa) and the fern leaf peony (Paeonia tenuifolia).

There are several reasons why the peony may fail to bloom. Some of the most common reasons are listed below.

  • The plants are too young or small. Newly planted peonies may not flower for 2 or 3 years. They need to grow and establish before they can flower.
  • The plants may be planted too deep. The eyes of the peony should not be more than 1 to 3 inches below the soil surface. If the eyes are deeper, dig up the peony plants and replant.
  • Plants may have too much competition from surrounding trees, shrubs, or even other peonies. Peonies should be spaced about 3 to 4 feet apart.
  • The plant received too much shade. Peonies bloom best in full sun. Move the peonies to a sunny location in September.
  • Too much nitrogen fertilizer was applied. Excessive amounts of nitrogen promote excessive vegetative growth and inhibit flower formation. Peonies can be fertilized in early spring when new growth is 12 inches tall and again immediately after flowering. One-fourth cup of a complete fertilizer (5-10-5) fertilizer can be worked into the soil around the crown of the plants and watered in. Be careful to avoid getting the fertilizer within 6 to 12 inches of the crown as young shoots and crowns are very susceptible to fertilizer burn.
  • Plants are undernourished so they are weak and small. Apply proper type and amount of fertilizer at appropriate times.
  • Buds appear, but do not fully develop. A late frost or freeze damages or destroys the developing flower buds. Very dry conditions during bud development may cause buds to abort. Water thoroughly by soaking the soil to a depth of 12 to 18 inches. This will require about 2 inches of slow, gradual irrigation.
  • Botrytis blight and Phytophthora blight are 2 common and important problems of the peony. Good sanitation practices like removing foliage in late fall or winter will help this situation. Do not compost any shoots or leaves suspected of a blight problem. Fungicides can be used to control the botrytis blight.



This article originally appeared in the May 10, 2002 issue, pp. 58-59.

Year of Publication: 
2002
Issue: 
IC-487(10) -- May 10, 2002