Because peony plants live for decades, they should be considered a permanent addition to your landscape, not unlike planting a tree. Proper planting will ensure flowers for years to come.
Herbaceous peonies are best planted in fall or earliest spring, as bare-root plants consisting of compact rhizomes with thick, fleshy roots and several “eyes” (growth buds). Tree peonies, nearly all of which are grafted onto herbaceous peony roots, may also be purchased bare-root and planted in fall or spring. However, many growers offer container-grown tree peonies that can be set out at any time the ground isn’t frozen.
Choose a site in full sun, or light afternoon shade in the Lower South.
Choose a sunny, well-drained spot free from competing roots of nearby trees and shrubs. For each rhizome, dig an area 11⁄2–2 ft. wide, loosening and turning the soil to a depth of at least 1 ft. Work in copious amounts of organic matter—such as garden compost, composted manure, or chopped leaves—to which you’ve added a cup of super-phosphate.
Position herbaceous peony roots so that the eyes are exactly 1 in. below the soil surface; deeper planting may reduce flowering. Make sure each rhizome has at least three eyes; rhizomes with fewer eyes take a long time to bloom. Set tree peonies so that the graft line is 3–4 in. below the soil surface (the object is to get the shrubby top to root on its own). Mulch peonies in spring to cool the roots and retain soil moisture. Plants usually don’t bloom the first year, so be patient.
Peonies should bloom every year after their first season if fertilized twice annually. Feed plants with a low-nitrogen fertilizer, such as 5-10-10. Spread about ½ cup around mature plants in spring when the shoots are beginning to emerge. Reduce the amount to ¼ cup around new, young plants. Repeat in fall. Alternatively, top dress with an inch of compost in spring before mulching; repeat in fall.
The good news is that deer seldom browse peonies. However, a fungal disease called botrytis sometimes appears during cool, damp weather. Flower buds blacken and fail to develop, and stems wilt and collapse. To prevent the problem, make sure there’s adequate air circulation around the plants, and clean up the garden in autumn, disposing of all fallen peony leaves and old mulch. As new growth emerges in spring, spread fresh mulch, and spray it with a copper fungicide.
As buds begin to enlarge and grow top heavy, support stems with subtle wire stakes or branches left over from pruning. Stick them into the soil to support the heavy blooms, especially during spring rains.
To gather peony flowers for bouquets, cut them just as the buds begin to open. Leave at least three leaves behind on every stem you cut, and don’t remove more than half the blooms from any clump. This preserves sufficient leaf surface to build up food reserves for the following year. Promptly removing spent flowers before they set seed also aids future flowering.
WHY DIDN’T MY PEONY PUT ON A SHOW?
Poor flowering has many possible causes, including these: The plant is too young (wait awhile); planting depth is too deep or too shallow (lift during dormant season and plant at proper depth); flower buds were killed by a late freeze (wait until next year); location is too shady (move to a sunnier spot during dormancy); weather was too hot too soon (plant early-flowering types); plant has nutrient deficiency (apply fertilizer); clump has been moved or divided too often (leave it alone).
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