Peonies (Paeonia sp.) have been cultivated for more than 2,000 years. Peonies were first grown in China and are now grown worldwide.

The large, showy and fragrant flowers of peonies bloom in late May or early June along the Front Range. Many colors and flower forms are available. Garden peonies are available in single-flowered, semi-double, Japanese, and anemone-type blossoms. These groups are distinguished by the number of petals and the extent to which the stamens are petal-like. Flower colors include coral, cream, crimson, pink, purple, rose, scarlet, white and yellow. The flowers are excellent for cutting and displaying in the home.

Peonies are long-lived, but slow-growing at first. Garden peonies will usually begin blooming within three years after planting. Most herbaceous peonies grow 2-3’ tall with a 3-4’ spread when mature. Tree peonies, technically shrubs, grow to a height of 4-5’ under normal conditions.

Most peonies have very attractive foliage that makes them a useful addition to the landscape all season. Use peonies as specimens in borders and herbaceous hedges.

Peonies grow best in cool climates because winter chilling is required for dormancy. The plants prefer full sun, but will tolerate light shade. Herbaceous peonies need at least six hours of full sun a day to promote blooms. Flower size will decrease due to root competition from nearby trees and shrubs. Peonies prefer a well-drained soil with a pH of 6.0 to 7.0.

Well-drained, loamy soil is best for peony growth. Well-drained soil is vital to avoid root rot and fungal diseases. If your soil is heavy clay, amend with compost, such as finely ground pine bark or composted manure to improve drainage and organic matter content.

The best time to plant peonies is in September before temperatures become too cool. Purchase peony divisions containing 3 to 4 “eyes,” which are root nodes. Divisions with only one or two eyes normally take longer to flower, up to five years. Make sure the divisions are free from rot or disease when planted. Trim away any soft spots with a sharp knife.

It is suggested to plant peonies approximately four feet apart to accommodate mature plant spread. Dig a hole 12 to 18 inches deep and 12 inches wide. Replace part of the soil in the form of a cone at the base of the hole and then spread the roots from the peony division over the cone. Set the roots so that the tip of the eyes (swollen pink or reddish buds) will be no deeper than 1 inch below the surface of the soil. Failure of blooms is likely a result from being planted too deeply.

Tree peonies should also be planted in fall. The graft union should be an inch below ground level. Mounding soil around the base of the tree peonies the first season will protect the graft union from cold temperatures.

Watering peonies thoroughly and deeply every 10 to 14 days will encourage deep rooting. Once established, peonies are very drought-resistant.

Apply a low nitrogen fertilizer such as 5-10-10 at the rate of 1/2 cup per plant in spring when the stems are 2 or 3 inches high. Over-fertilization, especially with nitrogen, can result in weak stems and reduced flowering.

When working around the plants in the early spring, be careful of the tender emerging shoots, usually dark red in color.

Larger flowers may be obtained by removing all but the large terminal bud. Peonies fail to bloom because they may be planted too deeply, lack nutrients (fertilizer), have low vigor from excessive nitrogen applications, may be competing with other roots, or they may be too shaded. Peonies can also suffer from botrytis blight, a fungal disease resembling gray mold.

Remove flowers as soon as they fade to prevent seed development, which can decrease food reserves. The faded flowers should be removed just below the flower blossom, leaving as much foliage as possible

In the fall, after frost, cut back the dead stems of herbaceous peonies down to 3 inches from the soil surface. This is very important if you have had any disease problems, and discard the stems. Do not add the pruned stems to the compost pile.

Never cut back tree peonies in the fall. Tree peonies are shrubs that will not grow back if they are cut down.

Peonies may be left undisturbed for many years. Peonies do not respond well to transplanting and reestablish slowly. Divide and replant only after they become crowded; usually after 10 to 15 years. If you want to divide or move peonies, do so in the fall. Carefully lift the clump and wash away the soil to expose the eyes. Using a clean, sharp tool, divide the clump into sections, each with three to five eyes and good roots. Replant immediately.

Most peonies need support to prevent the stems from flopping under the weight of their flowers. Commercial hoops are available for this purpose. You can also use a ring of three or four stakes and attach the plants to the stakes for support. Use stakes that are 6 to12 inches shorter than the plants so they will not be visible.

To cut peonies for a flower bouquet, clip the flowers in the soft bud stage. The buds should feel like soft marshmallows. Leave at least 3 leaves per stem on the plant. Re-cut the stems at an angle under warm water and strip off the leaves that will touch any water in the vase. Flowers should open within a day of being placed in a vase.

Cutting flowers for enjoyment in the home can also reduce the flowering in future years. Do not cut more than one-third to one-half of the flowers for cut flowers. Leave as much foliage as possible on the plant.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

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This page updated:  June 28, 2006