I first met Kasha at a dinner party I had for a few friends back in the early 1980s. At the end of the party, I offered her a tree peony blossom from my modest garden, hoping it might cast a romantic spell. It did. And not too long afterward, we began making plans for our wedding and the peony garden we would nurture together.

Our search for a proper garden site took more than a year. This paled in comparison to our search for plants. We specifically wanted to grow Chinese tree peonies that were not readily available in the U.S., so for years, we wrote to individuals and organizations in China. When we finally found someone, they insisted that we purchase several hundred plants. Wanting only a few of the best specimens, we scrambled to sell the rest. But through the years, our passion for tree peonies has blossomed into a full-time business.

Herbaceous peonies and tree peonies: Distinctly different plants

Peonies come in two basic types: herbaceous and tree forms. Herbaceous peonies grow to 4 feet, have flowers 6 inches in diameter, and are easy to propagate by division. They thrive in USDA Hardiness Zones 4 to 7 (–30°F to 0°F), and may have 40 or more flowers on a mature plant. Most bloom in early to mid-June and die back to the ground after first frost.

The tree peony, however, is a distinctly different plant. Tree peonies are woody shrubs; some grow 10 feet high without support. Their flowers—which come in a multitude of shapes, colors, and fragrances—are much larger and usually bloom two weeks earlier than herbaceous peonies. Although they lose their leaves in the fall, they maintain a graceful branching structure throughout the winter. Tree peonies can be grown in USDA Hardiness Zones 3 to 9 (–40°F to 20°F).

Tree peonies prefer dappled shade and good drainage

Unlike herbaceous peonies, which bloom best in full sun, tree peonies prefer partial shade, with three to four hours of sunlight. The plants grow faster in sun, but the flowers burn and vanish in a day or two. On occasion, when we do plant tree peonies in full sun to spur plant growth, we shade the blooms with a parasol or cloth awning, which rewards us with blooms that last a week to 10 days.

Tree peonies need a well-drained location, such as a hillside; standing water will kill them. And while they are not particular about soil acidity, a pH range of 6.5 to 7.0 is ideal.
Unlike herbaceous peonies, tree peonies do not require a freezing period to bloom, but rather a rest period of several weeks with temperatures of 35°F to 40°F. For this reason, they thrive as far south as Tuscaloosa, Alabama. They are hardy as far north as southern Minnesota, where winter ­temperatures can fall to –30°F.

Plant peonies in the fall

Fall is the time to plant and move all peonies. Plant your tree peonies at least six weeks before the ground freezes; spring planting simply does not allow time for roots to develop, so they are unable to support emerging foliage. As a result, spring-planted peonies often weaken or die, giving them an undeserved reputation of being hard to grow.

To plant tree peonies, dig a hole about 2 feet in diameter and in depth. Build a hill in the middle of the hole and spread the tree peony’s roots over it. Use good garden soil with plenty of organic matter to refill the hole, watering thoroughly when half filled and finished. Make sure all shoots are underground; it’s actually difficult to plant tree peonies too deeply. And remember, tree peonies can grow to considerable size, so space holes about 5 feet apart. If plants are subject to heaving in your climate, it’s smart to mulch your peonies the first year.

Tree peonies are heavy feeders

Since tree peonies have a lot of leaves and large flowers, they tend to be heavy feeders. Although we don’t fertilize them at planting time, we do feed them with compost in subsequent years. With the exception of fresh manures, which need time to break down, any available compost should do.

Rather than layering the compost on top of the soil, we dig a 1-foot-deep and 1-foot-wide trench along the drip line of the plant, and fill it with the compost. In a year or two, once roots have grown into the trench, we repeat the process further out. Each spring, we also feed our tree peonies with a foliar spray, such as seaweed or fish emulsion. After blooming, we water the plants with this same solution.

Tree peonies are plants with enormous vitality. Even if you run over them with a lawn mower, they’ll usually come back. With proper care, they’re virtually pest- and disease-free. After blooming, we deadhead the flowers, and in the fall, we take all the fallen leaves away. This cleanup helps prevent botrytis from infecting the plants in the spring.

We know of only one insect pest that preys on tree peonies: the rose borer. It works its way into the pith of older plants and deposits its eggs from spring to fall. If you see its telltale hole or a wilted branch, cut away the affected wood.

Older plants provide the blooms

Young tree peonies do not bloom. For this reason, we recommend that you purchase plants at least three years old for a first or second year show of color.

There’s another good reason to purchase plants. Tree peonies are difficult to propagate. Although many single and semidouble cultivars produce fertile seeds, the offspring often revert to the species, losing the desired characteristics of the parent plants. Even if they don’t, it can take up to seven years for a plant grown from seed to produce flowers.

The most widely accepted method of propagation is grafting new stem growth, or scions, onto root stock. Another method, with which we have had some success, is branch layering. It’s relatively easy to propagate low-growing and spreading plants, but is not an option for upright varieties.

While tree peonies may be challenging to propagate, established plants are easy to grow. They require little attention, yet can provide years of beautiful, fragrant flowers.

—David Furman and his wife, Kasha (who contributed to this article), collect, grow, and sell Chinese tree peonies at Cricket Hill Garden in Thomaston, Connecticut.