Growing Peonies                                                                           OH 58

Leonard Perry, Extension Professor

One of the most outstanding perennial flowers that is grown in the garden is the peony. Even though this plant seems to have been grown forever, it still remains very popular today. Of course, there are reasons for this and even though there are those gardeners who do not use this plant in their gardens, they certainly should. There are few perennials that can offer beautiful flowers in the spring and provide good foliage throughout the summer.

The peony is a hardy perennial that, once it becomes established, will flower for many years with little care. They are extremely hardy and easily withstand the winter conditions in Vermont. Peonies are considered by many gardeners to be the backbone of any perennial border because they do produce good foliage and flowers. The plants have long supplied cut flowers for use in the home or on cemetery plots.

The plants are either planted as single specimens mixed among other plants or in clumps or masses. They may be planted in rows forming a background for smaller plants. There are basically two forms of peonies: Herbaceous (Paeonia officinalis), and Bush or Tree (Paeonia suffruticosa). The herbaceous type grows to a height of 2 to 4 feet and the tree form reaches a height of 4 to 6 feet. Most gardeners seem to have much greater success with growing the herbaceous forms rather than the tree form. There is nothing more spectacular, however, than a mature tree peony in full bloom, and if the plant hasn't been used in the landscape, it should be given a try.

The herbaceous peonies are grouped into five types--based on the shape of the petals: single, semi-double, double, Japanese, and anemone. The single (or Chinese type) is characterized by one row of broad petals that surround a cluster of yellow pollen-bearing stamens. Some of the other flower types have central petals in the place of stamens. The semi-double peonies have broad central petals. The double peonies have central petals that are as wide as the outer ones. Japanese peonies have long, thin, central petals, while the anemone type have broad central petals.

Tree peonies produce many flowers on single, shrub-like plants. The centers of the flowers are yellow, pink, or red with the petals mottled at the base. Contrary to the herbaceous peonies, which die down in the fall when freezing weather arrives, the stems of the tree peony remain alive all winter.

There are many different cultivars (varieties) available within the various types of peonies. By careful selection, the flowering period can be spaced out over a longer period of time. Colors available for herbaceous peonies are white, yellow, cream, pink, rose, and deep red. Tree peonies come in colors such as yellow, pink, white, rose, crimson, scarlet, purple, and deep purple.

Peonies, as previously mentioned, are relatively easy to grow. As with most perennial flowers, the one prime
prerequisite for good growth and flowering is a well-drained soil. This may require adding organic matter--such as coarse sphagnum peat moss, well-rotted manure, or similar material--to the soil before planting. A good soil mixture might be three shovels of soil, one shovel of organic matter, and a source of phosphorus, such as a couple of tablespoons of superphosphate.

Light is another very important factor on which the successful growing of peonies depends. The plants will grow and produce good foliage in shady locations, but the flowering will be sparse or non-existent. Select an area that receives sunlight at least 6 to 8 hours per day. Planting where there is good air movement will also reduce the chances of having disease problems.

Once the planting site has been selected and the soil prepared, the plants can be planted. Peonies are generally planted in the fall, but they may also be available in spring as potted plants. For those herbaceous peonies obtained in the fall, be sure the tuber has three to five buds or "eyes" present. They will be bright red in color. Tree peonies are grown either from seed or grafts, with the more desirable way for the home gardener being grafted plants. Herbaceous peonies with three to five "eyes" will generally flower the second year after planting, while it will take three years for a grafted tree peony.

Set the tuber of the herbaceous peony so that the buds or "eyes" will be between 1 and 2 inches below the surface of the soil. This is most important because if the plants are planted too deep, beautiful foliage will be produced but few, if any, flowers. Tree peony tubers should be planted so that four or five inches of soil covers the graft. The graft can be determined by the ridging on the stem and the different texture of the bark. By planting deep, the grafted section will establish its own roots in the soil.

After planting, the soil around the plants should be thoroughly watered. If the planting is done in the fall, it would be a good idea to mulch the plants with some organic material, such as straw, coarse sphagnum peat moss, shredded bark, wood chips, or something similar. Apply 2 to 3 inches of material.

In the spring when the plants start to grow and the shoots are three to four inches high, apply a complete, dry synthetic fertilizer such as 5-10-5 or 10-10-10, or organic fertilizer such as 5-3-4, at the rate of 3 to 4 pounds per 100 square feet of bed area. Water the fertilizer into the soil immediately afterwards. High-analysis soluble fertilizers may also be used; apply them at the rate given on the container. One application of fertilizer per year is generally adequate to maintain good plant growth and flowering.  Too much fertilizer, especially nitrogen, and plants may have gorgeous leaves but no blooms.

Peonies get few problems.  Contrary to garden myths, ants cause no harm to buds, nor are responsible for them opening.  They are merely seeking nectar in the flowers.  If buds “blast”, turning brown and failing to open when pea-size, this could be from dividing the previous fall if plants are young.  Buds form the previous year in root crowns, so dividing may disrupt this process, or plants may need more developed roots before blooming.  This problem in mature plants can be caused by too much shade, decreased soil fertility, and either dry or cold after a harsh winter.  If stems suddenly wilt and turn brown, this could be caused by botrytis (gray mold) blight from wet and cool springs.  Prune and discard affected stems. Warm and drier weather solves this problem.

Peonies--like many garden perennials--are easy to propagate, so if additional plants are desired or if the clump has become crowded, division of the clump is recommended. Dig the plant and separate the tubers being sure each one has three to five buds or "eyes." Any damaged tubers, or those showing signs of disease, should be removed and the good tubers planted the same way as described earlier for new plants. In general, peonies usually do not need to be divided for 10 to 15 years, if even then.  Only divide if plants are too large for the space, need moving, or have poor vigor and fewer blooms than previously.

(Originally adapted from James L. Caldwell, Extension Horticulturist, The Ohio State University)
 

Prepared 06/09

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