HOW TO GROW PEONIES

Paeonia lactiflora. Photo by: PaylessImages / 123RF.

Zones:

There are garden-worthy peony varieties for Zones 2 to 8.

Types of peonies:

There are three types of peonies: herbaceous peonies (bush peonies), tree peonies and Itoh peonies (intersectional peonies). Compare them in detail here: Types of Peonies.

Height/Spread:

Herbaceous and Itoh peonies grow 1 to 3 feet tall, with a similar spread, while a mature tree peony can reach 4 to 7 feet tall and 4 to 5 feet wide.

Exposure:

Most peony plants are sun-lovers. “They require almost nothing but full sun and patience,” says Kathleen Gagan of Peony’s Envy in New Jersey. However, tree peonies prefer light shade during the heat of midday, which encourages the blossoms to linger 10 to 14 days, rather than fading in a blink (two to three days) in full sun. In China, parasols are enlisted to protect the delicate flowers from sun.

When do peonies bloom?

Peony season begins with shoots and leaves emerging, but the real show is when the peony flowers bloom in late spring. In most locations, peonies will bloom in April, May or June. Expect tree peonies to bloom first (around Mother’s Day), followed by herbaceous varieties (around Memorial Day) and then the intersectionals. If you include all three types in the garden—tree, herbaceous, intersectional—you can enjoy peony blooms for up to seven weeks.

Flower color:

Peonies are available in colors ranging from white, pink and red to coral, maroon and yellow. Many peony flowers change color as they open, so make sure to check them daily to appreciate their shifting hues.

Fragrance:

Many peony flowers are fragrant. Their scents can differ between cultivars—some are scented sweetly of lemons, some have enticing citrus smells, and some are described as slightly spicy. Words like delicious and confectionary are often used to describe the smell of a peony flower. Decide how strong you want the scent—some peonies are lightly scented, while others have a heady fragrance. For example, Chinese tree peonies have a stronger fragrance than Japanese tree peonies.

Pests and diseases:

Fortunately, peonies are deer and rabbit resistant. Unfortunately, they are susceptible to botrytis blight, a fungus that can cause young peony shoots to rot, unsightly spots on leaves and prevent buds from developing. Learn more about issues that can arise when growing peonies in the Missouri Botanical Garden's guide to peony problems.

If planted well, herbaceous peonies will happily send up new shoots each spring for decades. Photo by: gutaper / 123RF.

When to plant peonies:

Plant bareroot peonies in the fall (prior to the first frost) and they'll have the best chance of blooming the following spring. Spring planted peonies may not bloom for two years or more.

Where to plant peonies:

Picking the right spot for your peony plant is essential to its success. If sited incorrectly, deep roots make transplanting of mature peonies difficult or impossible. Aside from plenty of sunlight and nutrient-rich soil, you’ll want to make sure peonies are planted in an area where you can enjoy their gorgeous flowers. Herbaceous and intersectional peonies should be planted in a spot with at least five to six hours of full sun per day. However, plants that produce single and anemone flower forms may benefit from some afternoon sun protection. Furthermore, because peonies hate wet feet (roots standing in water), “a slope or raised bed is preferable to a very flat site,” says Kasha Furman of Cricket Hill Garden. And don’t forget to plan ahead and give tree peonies plenty of room—most grow to five by five feet in their 10th year.

Tip: The experts from the University of Michigan’s Peony Garden at the Nichols Arboretum recommend planting peonies far away from large trees and shrubs as they do not like to have root competition.

What type of soil is best for peonies?

Some gardeners have success growing peonies in their native soil, but most experts recommend amending with organic matter before planting. Proper soil preparation will make it so you don’t have to fertilize for the first few years of your peonies life. No matter what, ensure that the soil is well-draining, peonies will not do well with soggy roots.

Here are some tips for improving your soil:

• Herbaceous peonies love potassium; a 5-10-10 slow release fertilizer is a good choice.
• Peonies are heavy feeders and strongly prefer a sweet or alkaline soil, which may require adding lime or wood ash. “The plant does not uptake the nutrients as well if it’s in an acid environment,” Furman explains.
• Additional trace minerals (such as Azomite®) will inspire tree peonies to increase their flower size, bud count and ratio of double flowers, and to intensify flower color.

How deep to plant a peony:

The depth at which you plant your peony will depend on the type of peony and your climate.

Here are the planting depths for each type of peony:

• Herbaceous peonies: Position these with their “eyes” (next year’s buds) ½ inch (in warmer zones) to 2 inches (in cooler zones) below the soil surface.
• Tree peonies: Plant deeper than herbaceous peonies. Gagan suggests digging a hole 2 feet deep and 1 foot wide (after amending the soil with organic matter). Position with the graft 4 to 6 inches below ground level, so that the “nurse” herbaceous peony rootstock will die away.
• Intersectional peonies: Plant them just below the soil surface, 1/2 inch in warm zones, 1.5 inches in cooler zones.

Can peonies be grown in a pot?

Peonies are happiest in the garden, but can be grown in pots if given the proper attention. Select a large container with plenty of drainage holes. In colder areas, bring potted peonies in for the winter to protect them from freezing temperatures; plants in containers are more susceptible to frost damage. Additionally, you will need to water more frequently during the growing season, as containers dry out quickly.

Herbaceous and intersectional peonies should be cut back in the fall. Photo by: photowind / Shutterstock.com.

Should I prune my peony?

Unlike roses, peony bushes do not require precise pruning to thrive. Often pruning is only necessary in the event of damage or disease. Both herbaceous peonies and intersectionals should be cut back at the end of the growing season. Cut your herbaceous peonies all the way to the ground, but leave 4 to 6 inches of stem on your intersectionals.

For tree peonies, a dense snarl of branches can lead to doom. After five years, remove suckers from the center of the shrub to thin out growth and promote better air circulation. Do not cut back tree peonies until they are well established—they are slow growing, so every inch is precious. Pruning during the first two to three years will just hinder their progress and slight you on next year’s display. When pruning tree peonies, take care not to cut the woody stems—they bloom on old wood.

Disbudding peonies:

If you want large flowers, remove the side-buds that develop near the base of each terminal bud. However, if you want to prolong the blooming season, leave the side-buds alone (they will bloom later than the terminal buds).

Can I divide my peony?

Peonies do not need regular division for successful blooming. However, if you’d like to have more peonies, you can divide your mature plants as a form of propagation. The best time for dividing peonies is in the fall when the plant is nearing dormancy. Roots cut into pieces with 3-5 eyes have the best chance of success. Learn more about dividing peonies.

Do peonies require complex staking?

Many peonies should be staked to support heavy blooms, especially if you live in a rainy climate. Herbaceous peonies can be supported with a peony ring, while tree peonies are more suited for the use of bamboo stakes and natural twine. If this sounds like too much hassle, there are many varieties of peonies that feature strong stems that don’t require staking.

How often should I water my peony?

Peonies are not overly thirsty plants—in fact, overwatering can lead to problems. Give your peony bush excellent drainage and begin watering in spring if you go more than two weeks without rain. Then, provide weekly, deep watering throughout the dry summer months (one inch at each watering). Continue watering after flowering to ensure vigorous plants the following year. There is no need to water once they have gone dormant.

Should I mulch my peonies?

In very cold climates, peonies may benefit from a loose winter mulching with organic matter such as pine needles or shredded bark. Keep mulch a few inches away from the base of the plant. Remove the mulch in spring to allow new growth at the soil surface. For tree peonies especially, winter protection with burlap and a 3 to 4 inch layer of mulch (pulled aside in the spring) is wise in Zone 4 and colder parts of Zone 5.

Why didn't my peony bloom?

Many gardeners have difficulty understanding why their peonies don’t bloom. Here are the most common reasons:

• They are planted too deeply
• There isn’t enough sunlight
• Your soil is heavy on nitrogen
• The plants are still young

Peonies and ants:

Peony buds secrete a sweet nectar that attracts ants. The ants do not hurt the plant and they aren’t required for the blooms to open. If cutting peonies to take indoors, gently rinse the blossoms in a bucket of water to get rid of the ants.

Leaf curl:

When a peony's leaves curl it is a sign of stress, caused by lack of water, a virus or unusual weather conditions. Many plants recover from leaf curl if the issue is corrected and go on to bloom normally.