Peonies are one of our most beloved perennials, giving us magnificent blossoms of white, soft pastels, or deepest red in spring and early summer, with a dividend of handsome, compound leaves that remain attractive throughout the season. Peonies are classified in two main groups the well-known herbaceous kinds discussed here, which the completely to the ground in winter, and the less common tree peonies, a shrublike form with persistent woody stems. Peonies are long-lived, reliable, and extremely hardy; in fact, they bloom best in regions with cold winters (USDA Zones 3-7). In milder climates (Zone 8 and the cooler parts of Zone 9), early-blooming varieties flower more consistently than mid- or late-season sorts.
It’s best to plant peonies in fall, when they are dormant. Mail-order and local nurseries offer bare-root divisions during this season. Spring-planted peonies may fall to flower for several years, and may even the if they put out new shoots before their roots become established.
1. SELECT A SITE Choose a site with well-drained soil away from the competing roots of trees and shrubs. It is also wise to avoid very windy areas, since peony stems are vulnerable to breakage when heavy with buds and flowers. Give each plant an area about three feet in diameter.
In most regions a site in full sun is best, though if your spring bloom season tends to be hot and dry, you should choose a spot that gives the plants some afternoon shade.
2. PREPARE THE SOIL Peonies bloom most prolifically if left to grow undisturbed in the same location for many years, so planting in well-prepared and enriched soil is important. Dig a planting hole about two feet across and 18 inches deep. Mix several shovels of compost or well-rotted manure (fresh manure harms the roots) into the bottom of the hole. Fill the hole halfway with topsoil mixed with more compost and a cup of bonemeal. If your soil is acidic, also mix in about a cup of ground limestone. Peonies like a pH of between 6 and 7.
3. PLANT THE PEONY a bare-root peony division is a section of rooted crown with, ideally, three to five firm, dark red growth buds called eyes. Each bud gives rise to a stem in the spring. Divisions with fewer eyes will grow but are slower to form a goodsize, blooming plant.
Planting depth is critical, because setting the division too deep prevents flowering. Generally, the eyes should be covered by no more than one and one-half to two inches of soil. However, if you garden in a mild-winter climate, position the eyes so they will be only one-half to one inch below the soil surface, thus exposing the roots to as much winter cold as possible. Scoop out several inches of soil from your prepared planting hole and set the division in place. After double-checking the depth of the eyes with a ruler, work soil carefully but firmly around the roots. Make sure there are no air spaces that could allow the plant to settle too deeply.
4. CARE FOR THE PLANT Water the plant in with a gentle stream from a hose. Then surround it with a light mulch, such as chopped leaves or evergreen branches, to help reduce competition from weeds. In cold-winter climates, mulching also helps prevent alternate freezing and thawing of the soil and subsequent heaving of the young plant. In mild-winter regions, mulch helps keep the summer soil temperature down and reduces water loss from evaporation. Remove the mulch in winter so that the plant gets properly chilled.
Don’t expect full bloom the first year or so after planting a peony. By the third year, however, it should reach top form and blossom gloriously for many years.