By some estimates, there are as many as 33 different species within the genus Paeonia, known collectively as peonies. Most are herbaceous perennials, though a few are woody shrubs. Peonies have tuberous roots that are a combination of thick storage roots and thin roots designed to absorb water and nutrients. Careful handling of these roots is critical to planting or transplanting peonies, as well as when you are dividing plants to propagate them.
Peonies are categorized in many different ways, such as by flower type or by growth habit. In addition to the familiar garden-variety herbaceous peonies with all their flower variations, there are special types such as fern-leaf peonies (Paeonia tenuifolia), a particularly sensitive and prized species, and tree peonies, which are woody, upright forms. These types have some special planting needs.
|Plant Type||Perennial flower|
|Sun Exposure||Full sun|
|Soil Type||Well-drained; adaptable|
|Soil pH||6.5 to 7.0|
|Bloom Time||Late spring to late summer|
|Flower Color||Wide range|
|Hardiness Zones||3 to 9 (depending on variety)|
|Native Area||Asia, Europe and Western North America|
How to Grow Peonies
Peonies are classic garden plants that can thrive for decades with minimal care when planted in a spot they like, in soil that meets their needs. One of the longest-lived of all garden plants, peonies are sometimes handed down from generation to generation in families. But it is very important to do the initial planting correctly because peonies can be temperamental about being moved once they are established.
Give each peony plant enough space to grow to maturity without being crowded. That means a 3- to 4-foot diameter for each plant. Peonies are especially prone to gray mold (botrytis) when planted too closely and air cannot flow freely between plants. Choose a location that is sheltered from strong winds. Plant your peonies well away from other trees and shrubs, since they don't like to compete for nutrients and water.
Peonies like a good chill in the winter. In order to set their flower buds, so peony roots should be planted relatively close to the soil surface—only about 2 to 3 inches deep. It may feel odd to leave roots so exposed, but peonies actually need this chilling to attain dormancy and set buds.
Bloom time for peonies varies from late spring to late summer, depending on variety, but all types are best planted in the fall, about 6 weeks before the ground freezes. This gives the plant time to settle in and establish roots before winter. This is especially true when planting bare root peonies or when transplanting, but even when planting potted peonies, fall planting gives better results than spring planting.
Peonies need a location that receives at least 6 hours of sun each day and a full day of sun is even better. Without sufficient sunlight, you’ll get fewer blooms and smaller flowers, and the plants will have a greater risk of fungal diseases, such as gray mold.
Peonies are very adaptable, but ideally, they like a well-drained, slightly acidic soil (6.5 to 7.0 pH). If you are planting in heavy, clay soil, amending with compost or a soil mix labeled for azaleas and rhododendrons will make it easier for your peony plant to settle in. Since peonies can remain in the same spot for upwards of 70 years, taking the time to prepare the soil before planting is time well spent.
Peonies need moist, well-drained soil to thrive. Ideally, they should receive 1 to 2 inches of water weekly. Mulch your peonies to help them retain water and lessen the likelihood of weeds.
Temperature and Humidity
Peonies prefer cooler areas (hardiness Zones 3-8 and do best when they experience cold winters. They can thrive in relatively wet areas but are not drought-resistant.
Feed lightly. An annual application of compost mixed with a very small amount of fertilizer around the base of the plant is all that is needed. When you do feed with compost and fertilizer, do it just after the plants have finished blooming.
Don’t smother peonies with mulch in winter. In the first winter season, you can mulch loosely with pine needles or shredded bark, but mulch should be promptly removed in spring.
Potting and Repotting
Peonies are typically purchased as potted plants in 1/2-gallon or 1-gallon containers at the nursery or as bare roots, often packaged with peat moss or wood shavings in plastic bags. The peonies offered at plant society sales or plant swaps are very often the tuberous bare roots.
When choosing potted peonies, look for healthy specimens without leaf spots or weak-looking stems. When planting from bare tuberous roots, make sure the root clump has at least 3 to 5 "eyes"—small reddish buds that resemble potato eyes. These eyes will eventually elongate and become the plant's stems. A mature peony should be at least 3 or 4 years old before it is divided into bare roots. Peony eyes start off as small reddish buds, similar to the eyes of potatoes. Tuberous clumps with only one or two eyes may still grow, but they will take longer to become established plants.
If an established peony needs to be moved, transplanting should be done carefully to avoid disturbing the roots any more than necessary. These plants can thrive in the same spot for decades, but moving one hastily can bring about its demise. As with any planting, fall is the best time to move a peony.
- At the new planting site, till up the soil 12 to 18 inches deep, and mix in a 4-inch layer of compost or peat moss.
- Water the peony plant with 1 inch of water one or two days before transplanting. Your peony must be well hydrated before moving it.
- Dig around the root ball of the peony using a sharp spade, getting as much soil as possible.
- Slide a tarp under the root ball to keep it intact, then lift the plant from the ground and carefully carry or slide it to the new location.
- At the new location, dig a hole that is twice as wide as the peony's root ball, and exactly as deep as the root ball.
- Plant the peony at exactly the same depth as it was in its old location. Backfill around the plant. Tamp the soil down with your hands, but do not pack it too tightly.
- Water thoroughly. Add a 3-inch layer of compost or mulch around the base of the plant. This will keep the roots moist and cool while the plant is establishing in its new location.
Peonies are best propagated by lifting and dividing the root clump, then immediately replanting the divided pieces. A peony may require this after about 10 years when it begins to lose its vigor and becomes root-bound. Here, too, fall is the best time for this activity.
- In the fall, just before you plan to divide, cut the foliage of the peony back down to ground level.
- Dig up the entire plant and remove as much soil as possible by soaking with a hose.
- Using your hands, manipulate the roots into dividable portions, each with three to five eyes, then use a sharp knife to cut the tuberous root clump into divisions.
- Cut away all the tiny roots on each division, leaving only the large, fleshy roots.
- Replant the divisions as soon as possible, following the instructions above.
Considerations for Fern Leaf Peonies
Fern leaf peonies are planted and cared for in a manner similar to standard peonies, but it is especially important to keep them well watered. Feed them each fall before the foliage fades with a mixture of bonemeal and compost. If you use commercial fertilizer, avoid products heavy in nitrogen, because this reduces flower production. In the first year or two, fern leaf peonies may die back in mid-summer immediately after flowering. This is expected and is no cause for concern. Fern leaf peonies take several years to mature and flower, so don't get discouraged. Fern leaves have especially sensitive roots, so use great care when moving or dividing them.
Considerations for Tree Peonies
Tree peonies like a slightly more alkaline soil than standard herbaceous peonies, and they do not want to compete with other shrubs. And do not cut them back to ground level in the fall.
Tree peonies need iron and phosphate and do well with an annual feeding of sulfate and bone meal in spring. Unlike herbaceous peonies, they need regular feeding with a 5-10-5 fertilizer.