How to Grow Peonies

Which peony you are planting

There are three main groups. Herbaceous peonies, mostly Paeonia lactiflora hybrids, are the familiar garden plants that die to the ground each winter and come back from fleshy roots. Tree peonies are woody shrubs that keep their stems year-round. Itoh, or intersectional, peonies are crosses between the two, with short woody stems that still die back in winter. This guide covers herbaceous peonies, the type most gardeners buy.

You will find them sold two ways. Potted plants from a garden center can go in the ground at any point in the growing season. Bare-root divisions, usually from mail-order nurseries, are a fall job. See when to plant peonies for timing by region.

Choosing the spot

Give peonies six to eight hours of direct sun. Nebraska Extension allows no more than two or three hours of shade a day, and shade is one of the most common reasons a clump stops flowering. In hot areas, Clemson notes that a little afternoon shade keeps the flowers from fading as fast.

Keep them out of the root zone of trees and large shrubs, which take the water and nutrients peonies need. The soil should be well drained and close to neutral or slightly alkaline. Wet soil leads to root rot, so in heavy clay or low spots, consider a raised bed. Plan for room: Wisconsin Extension spaces most peonies 3 to 5 feet apart, and good air movement between plants helps keep foliage diseases down.

Because a peony may stay in one place for decades, prepare the bed well. Nebraska suggests working the soil 18 to 24 inches deep and mixing in compost or other organic matter a few weeks before planting.

How deep to plant peonies

Depth is the single most important detail. Set the root so the eyes, the pink or reddish buds on top of the crown, sit 1 to 2 inches below the soil surface. Wisconsin warns that peonies often fail to bloom when the buds are deeper than 2 inches, and both Clemson and Nebraska set the limit at 1 inch. Planting too shallow has its own risk: Nebraska notes that eyes right at the surface can be killed by frost.

To plant a bare-root division:

1. Dig a hole about 18 inches wide and deep, and mix some compost into the soil you removed.
2. Refill part of the hole and water to settle it, so the root will not sink later.
3. Set the division so the eyes face up and will end up 1 to 2 inches below grade.
4. Backfill, firm the soil and water well.

With a potted peony, keep the soil level the same as it was in the container. Water new plantings during dry spells in fall. After the ground freezes, Nebraska recommends about 2 inches of straw over the first winter to prevent frost heaving.

Watering and feeding

Water young plants regularly but do not keep them soggy. Established peonies become quite drought tolerant. Clemson suggests a deep soaking every 10 to 14 days when rain is short.

Feed lightly. Extra nitrogen gives big leafy plants with few flowers. Clemson uses a low-nitrogen fertilizer such as 5-10-5 in spring when the shoots are 2 to 3 inches tall, and keeps fertilizer and manure off the stems.

Staking, deadheading and fall cleanup

Large double flowers get heavy, and Clemson finds most peonies need support to keep the stems from flopping. Use a commercial hoop or a ring of three or four stakes with ties. When you work around the plants in early spring, watch for the tender new shoots. Deadhead faded flowers after bloom so the plant puts its energy into roots rather than seed.

In fall, cut all the stems to the ground and throw them away. Do not compost them. This one habit does more against peony diseases than anything else.

Dividing and moving peonies

Peonies do not need regular division, and some clumps are never divided. If you want more plants or need to move one, do it in September or October. Cut the stems down, dig the clump carefully, wash off the soil and cut it into pieces with three to five eyes each. Smaller pieces take several years to reach flowering size. A moved peony often skips blooming the next year and then recovers.

Common problems

• No flowers: usually planted too deep. Also check for shade, tree-root competition, too much nitrogen, a recent move, or too little winter chill in zones 8 and 9.
• Botrytis blight: buds wither, and leaves and stems wilt and darken. Remove all top growth each fall and space plants for air flow.
• Leaf blotch and powdery mildew: purplish-brown blotches or white powder on leaves. Rarely serious; fall cleanup, good spacing and not overwatering keep them in check.
• Ants on buds: harmless visitors drawn to the nectar.

Peonies in the South and warm-winter areas

Peonies need a real winter to set flower buds. In the upper South they grow well with the right choices. Clemson recommends early-blooming cultivars, which open before hot weather and are less prone to botrytis, and finds single and Japanese forms usually outperform doubles there. Its list for South Carolina includes ‘Festiva Maxima’, ‘Coral Charm’, ‘Miss America’ and ‘America’. In the lower South and zones 8 to 9, some cultivars simply do not get enough chill to bloom. Texas A&M’s Bexar County office is blunt that San Antonio’s winters are too warm and its summers too hot for peonies.

If you want flowers for pollinators, Wisconsin notes that single and open-centered peonies give bees much easier access to pollen and nectar than tightly packed doubles.