Peony
Peonies were first cultivated in China several thousand years ago, preserved and protected in imperial gardens grown only for the delight of emperors. The Chinese word for them, “ShoYo” meant “most beautiful”. Today Minnesota gardeners can count on these royal perennials for an amazing show of magnificent spring flowers.
Peonies blossom in a variety of fabulous flower forms displaying lush attractive foliage in a wide range of growth habits. Peonies are long-lived, adaptable plants hardy to zone 3; they require a number of chilling hours below 40 degrees to break dormancy and bloom, making them ideal for cold climate gardens. They are highly pest and disease-resistant, and unappealing to deer as well. Once established they can withstand moderate periods of drought.
The two main types of peony are the herbaceous peony and the tree peony. Within the herbaceous peonies there is the common peony Paeonia officinalis, and Paeonia lactiflora and the named varieties, referred to as hybridized peonies. Varieties measuring less than 18” bred for today’s smaller gardens are sometimes called rock garden peonies. The tree peony Paeonia suffruiticosa is often called a mouton peony. Less common is the Chinese Paeonia lutea. Tree peonies crossed with herbaceous peonies are called intersectional hybrids or Itoh (after the Japanese breeder who accomplished this feat), exhibiting preferred traits of both plants.
Herbaceous Peonies
Herbaceous peonies behave as a perennial with their foliage dying back in the fall, while tree peonies are shrub-like with a woody stem that persists over winter. Herbaceous peonies start from a brown, tuberous root or crown, with eyes or buds pointing upward. Leaf shoots emerge from these eyes until the foliage is developed. Peonies have compound leaves arranged alternately on the stem. The leaflets are oval or lance shaped; early growth including the stem is tinged in pink to red. Mature leaves are dark green and glossy, giving the plant a bold and striking appearance even before flowering. The plant grows 2-3 feet in height.
Flower colors include many shades of white, cream, yellow, pink, coral and red. The silky flower petals can be cupped, rounded, ruffled or picotee. Many have prominent yellow centers and color-tipped stigmas. Five flower forms describing the arrangement of petals are recognized as single, semi-double, double, Japanese and bomb. The Japanese form is sometimes known as anemone, similar in shape to the actual anemone flower. While the bomb form seems to explode with numerous petals, the name is from the rounded form of bombe desserts popular in the 1920’s. Many peony varieties emit a sweetly scented fragrance.
Best Location for Herbaceous Peonies
Peonies should be grown in well-drained loamy soil high in organic matter. The site should receive 6-8 hours of full sun. Allot a permanent location to avoid disturbing the tuberous roots, while keeping in mind potential competition for water, nutrients and light from other plants and trees. A sheltered position will protect flower quality from rain and wind.
Best Care for Herbaceous Peonies
Plant Selection
Order bare root peonies in spring to plant in fall. Early ordering will assure a wide selection among varieties. Fall planting provides more time for root establishment to insure better bloom the following spring. However bare root peonies from local nurseries can be planted in the spring as well. Look for firm, healthy looking crowns with 3-5 eyes, without signs of rot. Containerized peonies can be planted at any time during spring or fall.
Planting
The old saying, “Peonies must grow well to flower well”, is true. Peonies should be given plenty of space for growth and air circulation; 2 feet apart for smaller varieties and 4 feet for standard varieties. Planting depth is very important; peonies planted too deep will produce buds that fail to bloom. The eyes should be planted facing up, never deeper than 1/12 to 2 inches below the soil line.
Peonies should be planted in friable soil, amended with compost, peat moss or bone meal prior to planting. The soil should be watered in to settle to avoid sinking the peony crown too deep.
Remove bare root plants from packaging, trimming off any broken or rotted areas. Soak in water for several hours. Potted peonies should also be soaked prior to planting if dry, taking care not to disturb the root ball. Anchor the crown in the hole and gently fill in soil and tamp down. Water in and check that eyes remain at the proper depth. Peonies may not reach their full flowering potential until their third growing season.
Water
Regular deep watering around 1 inch per week, helps to establish new plants; continued deep watering will result in lush plants with luxuriant blooms. Once established peonies can survive periods of drought but will flower with smaller blooms.
Mulch
When the ground warms up in late spring, mulch peonies with up to 2 inches of material such as compost, dried grass clippings, or shredded bark to conserve soil moisture and suppress weeds. When pulling back mulch the following spring take care to not break off emerging buds near soil line. The same care should be used when weeding around the plants
Fertilizer
Fertilize peonies with a low nitrogen fertilizer in spring when shoots first appear and then once again when flower buds begin to form, watering in well to dissolve granules. While organic fertilizers such as compost or blood meal are best incorporated at planting time, fish emulsion can be used after the fact if desired.
Best Cultural Practices for Herbaceous Peonies
Pest and Disease Control
Peonies are relatively care-free plants. Fungal diseases like botrytis blight and leaf blotch can occur during wet springs or in warm moist weather. Botrytis blight causes spots on leaves; stems soften and decay, buds turn brown and flowers fail to bloom. Leaf blotch symptoms include purple glossy spots on the upper surface of leaves. Both problems are controlled by removing and disposing of the infected parts. Providing better air circulation can help as well as drip irrigation to eliminate overhead watering.
Wherever there are peonies there will be ants, but contrary to popular myth ants do not “help” peony flowers to unfurl. Ants are attracted to the sugary liquid on the buds, and in turn protect the flowers from other insects. This relationship is described as synergistic. To rid the blooms of ants before bringing indoors, merely shake the stems or rinse carefully under water.
Pruning and Grooming
Deadheading old flowers enhances the appearance of peony plants, directing the plants energy to foliage and flower production rather than seed. Gardeners growing peonies for exhibition will often disbud, or prune the lateral buds to achieve a larger central flower. Oppositely, pruning the terminal bud will result in a greater quantity of smaller flowers on side shoots.
When foliage starts to deteriorate in the fall, it is tempting to trim it off. However it should be left until the first frost. Any foliage left is converting and storing energy for next year’s growth. Sanitation in the peony bed is important. Any diseased foliage should be pruned to control the spread of fungal disease. This material and any dead foliage on the ground should be discarded and not composted.
Staking and Support
The large, heavy flowers and long stems of the peony require support to stay upright and off the ground, especially during rainy and windy weather. Peony hoops are metal rings that are placed over the plant and driven into the ground at the beginning of the season. The hoop is quickly hidden from view as the foliage grows. Single and Japanese forms with lighters flowers do not require as much support unless the plant is very large.
Division
Peonies can be divided in spring or early summer, but it is best done in the fall. Peonies do not require division unless there is a reduction in flowering. Division can be a means to increase peony stock.
Cut off the stems and dig deeply to pull up the old clump. Hose off the clump and slice it with a sharp knife or shovel into sections; each section should have 3-5 eyes or buds. If fungal disease has been a problem, dip the root section in fungicide prior to replanting. Replant in the same manner as bare roots plants; avoid breaking off the new buds.
Special Uses
Peonies are among the most popular and beautiful cut flowers. Peonies can be cut and stored before use for up to 3 weeks. To do this, cut the flowers in the soft bud stage and refrigerate. For immediate use cut when flowers are ¾ open and plunge the stems into cold water. Some florists will sear the tips with a flame before arranging. Do not cut more than a third of the flowers off each plant to assure next year’s growth.
Creative Landscaping with Herbaceous Peonies
-Plant peonies together in a row to create an informal hedge or as a subtle divider between lawns.
-Use them as a shrub-like backdrop for annuals or shorter perennials.
-Underplant peonies with spring flowering bulbs; the emerging peony leaves will hide withering bulb foliage.
-Plant with smaller flowers and finer-leaved perennials such as nepeta (catmint), heuchera (coral bells) and dicentra (bleeding heart) for contrast with larger foliage and blooms of the peony.
-Plant above a retaining wall or terrace so that blooms can be enjoyed at eye and nose level.
-Include peonies in the cutting garden for voluptuous bouquets, the fragrance garden for their lovely scent and white peonies in the moonlight garden for an ethereal glow.
Tree Peonies
“Personification of the Evening Star”, “God of the North Wind”, and “Young Dancing Girl”, are just some of the poetic names of the tree peony whose exotic blooms have been celebrated through the centuries. Yet the tree peony is actually a deciduous shrub, hardy to zone 4, whose woody stems remain over winter. It is slow growing but long-lived, eventually maturing in 5-8 years to 3-5 feet in height and width depending on the variety. The foliage consists of compound leaves; with deeply cut pointed lobes emerging in reddish tones turning to green. Besides gorgeous shades of pink and red, they are available in unusual colors like yellow, maroon, purple, and green. Many varieties display a watercolor-like staining on the petals. The luxuriant, ruffled single and double flowers are large, 5-6 inches across and sometimes display contrasting centers or flares that showcase the mustard-yellow stamens. These flowers bloom around two weeks earlier than herbaceous peonies.
Best Location for Tree Peonies
Tree peonies should be planted in well-drained loose and friable soil, rich in organic matter. Tree peonies thrive in dappled sunshine or partial shade. They should be sheltered from mid-day sun as well as from drying winds; an eastern exposure close to a building is ideal. Their mature size should be kept in mind when selecting a permanent site.
Best Care for Tree Peonies
Plant Selection
Tree peonies can be purchased as bare root plants or in containers. Bare root plants should be planted in the fall to allow for root development prior to spring growth. Containerized plants can be planted any time spring or fall.
Planting
Bare roots plants should be soaked before planting. Loosen the soil and amend with organic matter such as compost or peat moss prior to planting. A slow release high phosphorous fertilizer can be incorporated at this time.(Ideally a soil test should be done before planting to determine if phosphorous is lacking in the soil to avoid problems with runoff) Dig a hole to approximately 2 feet deep and wide to accommodate the roots. Tree peonies are grafted; the graft union of the woody stem (scion) and the root (understock or nurse root) should be planted 4-6 inches below the soil line. The tree peony will eventually develop its own root system. Containerized tree peonies should be planted with the soil ball at ground level. Water in well after gently filling in soil.
Water
Regular deep watering around 1 inch per week, helps to establish new plants; continued deep watering will result in lush plants with luxuriant blooms.
Fertilizer
After the plant is established, a well balance slow-release fertilizer is recommended. Over-fertilizing will actually encourage foliage growth at the expense of the flowers. Fertilize as an herbaceous peony, at first emergence of growth and then again at bud formation. It may take several years to reach full flowering potential.
Mulch
During the growing season apply mulch to a depth of 2 inches to conserve moisture and suppress weed growth. For added protection in cold climates, increase mulch for winter to 4-5 inches, taking care not place it next to the stems.
Best Cultural Practices for Tree Peonies
Pest and Disease Control
Tree peonies rarely suffer from disease. However botrytis or tree peony wilt can occur in wet springs. Stems will wilt, followed by flower deterioration and gray moldy blotches on leaves. Control is to prune out the infected part. Regular sanitation is the best solution to this problem, keeping the area free of and disposing of fallen flowers, leaves and trimmings.
Tree peonies are not palatable to deer and rabbits.
Pruning and Grooming
Large flowers can become heavy after rains. Remove spent flowers to improve the plants appearance. Prune in late winter keep smaller, maintain shape and eliminate dead wood.
Creative Landscaping with Tree Peonies
-Create an informal hedge with freestanding plants or along fences.
-Tree peonies make great understory plants and combine well with other shade-loving perennials.
-A single tree peony makes a stunning accent, especially at the front door.
-Use singly or in groups when creating Asian-themed gardens.
-Cut flowers for beautiful bouquets.
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