You can cultivate gorgeous peonies this June

Peonies, with their huge, look-at-me blooms, are one of the glories of early summer. They’re also one of the easiest, most durable garden perennials.

“Once it’s established, a peony plant may live for decades,” said Sharon Yiesla, plant knowledge specialist in the Plant Clinic at The Morton Arboretum in Lisle. “Peonies are very hardy. They like our climate because they actually need a period of chilling in the winter.”

There have been peony plants along Joy Path near the Arboretum’s Thornhill Education Center for more than a century, since the time when the site was the country estate of the public garden’s founder, Joy Morton. He cultivated a large peony collection. Now there are also peonies in the Arboretum’s new Grand Garden, which is in its first blooming season this year.

There are three main types of peonies. Garden peonies, also called herbaceous peonies, are the most common sort. They are bushy green plants that die back to the ground each fall. Woody peonies, sometimes called tree peonies, are actually small shrubs that can have very large flowers. The peonies in The Grand Garden are Itoh peonies — hybrids in which herbaceous peonies are crossed with tree peonies, creating vigorous plants with bright flowers.

Peonies come in many cultivated varieties with a wide range of flower colors, including white, pink, yellow, peach and rosy reds approaching purple. They typically bloom for a couple of weeks in late May or early June, depending on the weather.

Here are some tips from the Plant Clinic for growing peonies.

Find a site in full sun. Peonies need at least 6 hours of direct sunlight a day. Make sure the site has well-drained soil with plenty of organic matter. “It’s a good idea to dig in compost to the area before you plant,” Yiesla said.

Allow for a large plant. A peony may take two or three years to reach its full size, which may be more than 4 feet wide. Read the plant label carefully. “Make sure you have enough space so the plant won’t be crowded,” Yiesla said. “Air circulation is important.”

Be patient. Peonies may not bloom for a year or two after being planted or transplanted. Whether they are planted in spring from pots or in fall as bare-root plants, they will take some time to become established. While you wait, water them regularly to help them spread their roots underground.

Support them early. Big fluffy peony flowers are heavy and their weight can bend the plant’s stems down to the ground, especially when the blooms are wet. To support the stems, install a wire peony ring or grid early in the spring and let the stems grow up through it. “The blooms of single peonies, which have fewer petals, are lighter and less likely to flop than double varieties with lots of petals,” Yiesla said.

Don’t worry about ants. Ants are attracted to peony blooms by their abundant nectar. The ants do no harm and may even protect the flowers from more damaging insects. “There’s no reason to treat peonies with any insecticide against ants,” Yiesla said. To avoid bringing ants indoors when you cut peonies for flower arrangements, “just hold the flower upside down and shake the ants off,” she said. The myth that peonies need ants to bloom is untrue.

Give them room. Although peony plants are relatively disease- and pest-resistant, they do sometimes suffer from powdery mildew. To deter this fungal disease, allow plenty of space for air circulation around peony plants. Clean up any diseased foliage in the fall and dispose of it outside your garden.

Protect the roots. Like most perennials, shrubs and trees, peonies benefit from a layer of mulch over their roots. Mulch keeps moisture in the soil, insulates the roots from extremes of heat and cold and slowly decays to enrich the soil.

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.