Peonies are herbaceous perennials that provide large blooms in shades of red, maroon, pink and white in mid-spring. For many years, gardeners were advised not to divide them. While it’s unclear where and when this taboo began, it can be classified as an old wives’ tale. Peonies are easy to divide, and the divisions grow readily into large plants when replanted in rich, well-drained soil.
A peony to be divided should be a mature plant, at least four or five years old, about 3-by-3 feet and healthy. Peonies can be left undisturbed for decades, but if you want to make more plants from a peony you have, the time to divide is in late August or early September.
Peonies bloom in mid-spring.
Use a spading fork to dig up the peony clump, digging about 8 inches back from the stems and about 18 inches deep. Wash the clump off with a hose so you can see the growing tips or eyes. Cut the rhizomes apart so each one has three to five eyes.
Peonies need sun and rich soil.
Peonies enjoy rich soil, so dig a generous hole and amend the soil with compost or composted manure. Add a handful of fertilizer, such as an organic 4-5-4 NPK formula, and mix it with the soil in the hole. Place the peony so that the eyes are an inch below the soil surface. Water well. Mulch the clump 1 inch deep with compost, straw or bark to protect it through its first winter.
Ants sip nectar but do no harm.
Peonies need full sun and yearly applications of compost. Give them good air circulation; don’t crowd them against each other or with other plants. This helps prevent botrytis, a common fungal disease. Ants are attracted to the sweet liquid secreted by peony buds but they do the plant no harm.