From the time their flouncy, flamboyant blooms burst on the scene in spring until their green, glossy foliage withers with the first fall frost, peonies (Paeonia spp.) transition from prima ballerinas to chorus-line dancers showcasing the summer's other perennial stars. In U.S. Department of Agriculture plant hardiness zones 2a through 8b, old-fashioned garden peonies (Paeonia lactiflora) continue to grace tumbledown farmhouse yards decades after those who planted them have moved on. Given the right growing conditions, garden peonies may live for a century.
Plant for Posterity
Once planted, peonies prefer to remain where they are. Think of them as foundation plantings to be enjoyed for generations, and select their sites accordingly. All peonies do best with at least six hours of daily sun. The ideal soil is loose, well-draining and organically rich, with a pH between 6.1 and 7.8.
To get peonies off to the best possible start, amend the soil before planting with well-aged, plant-based compost. Use a spade or garden tiller to work a 2- to 3-inch layer of the compost into the top 6 to 8 inches of soil. The Cornell University Department of Horticulture recommends using 60 to 90 pounds of compost for each 10 square feet of soil.
Unless they're forced to compete with other plants, peonies' roots usually store enough snowmelt or rainwater that occasional supplemental water is enough to see them through the growing season. Spacing them 3 to 4 feet from each other and well beyond the root zones of nearby shrubs or trees eliminates the competition. During dry springs and throughout each summer, a drink every two weeks is adequate. Water enough to wet the soil down to the base of the roots. Summer watering encourages healthy buds for the following year.
Rain-saturated peony buds may become brown and refuse to open. Supply them with raincoats of clear plastic bags.
Watering peonies at the base keeps the foliage dry, reducing the risk of fungal infection.
Fertilize for Flowers
Keep peonies vigorous and maximize their blooms with an annual spring dose of 5-10-10 fertilizer applied when their new shoots are between 2 and 3 inches high. Low in nitrogen and high in phosphorous and potassium, this formula promotes heavy blooms and healthy roots without stimulating excessive leaves. Spread 1/2 cup of the fertilizer granules on the soil around each plant, beginning 6 inches from the outside of the shoots and extending 18 inches over the root zone. Work the fertilizer into the soil with a cultivating fork and water thoroughly. Overfertilized peonies typically have weaker stems and fewer flowers.
Defeat the Droops
After heavy rain, an unsupported peony's flowers may flop to the ground as if the weight of the world were on their petals. To prevent disastrous drooping, collar each plant's young shoots inside a wire peony hoop with a grow-through grid. Sink the hoop's three legs into the ground so that it stands at about one-half the peony's mature height. As the plants grow, their leaves expand to cover the wire and their stalks stand up to wind and rain.
The Fond Farewell
As hard as it is to see them go, spent peony blooms develop seeds that steal food needed for next year's buds. As soon as flowers fade, remove them with clean, sharp stem cutters rinsed in rubbing alcohol between cuts to kill disease. Leave plenty of leaves; until dying back in fall, they'll continue manufacturing food. When their leaves do die, cut herbaceous peonies' stems back to 3 inches from the ground and dispose of them.