Peonies bloom early in the summer, producing huge, loose flowers that make great bouquets and smell wonderful. They are among the easiest flowers to grow, but sometimes they don’t bloom as profusely as you might like. Most problems stem from incorrect planting or overfeeding, though occasionally the age of the plants or insect pests can be the cause.
Plant peonies where they’ll get lots of sunshine. If they don't get at least six hours of direct light every day, they may never flower at all.
Plant the bulbs at the correct depth. Examine all the bulbs to locate the “eyes,” which are the places where new growth starts. Plant the peony bulbs under no more than two inches of soil. Peonies aren’t fussy about much, but they do demand that you plant them at the correct depth. Planting them too deep almost guarantees that they won't flower well.
Feed the peony plants lightly. If you overfeed your flowers, they will put most of their energy into producing leaves rather than blossoms. Bachman’s Floral, Gardens and Gifts recommends that you fertilize the plants only once each season with perennial fertilizer, superphosphate, or an organic fertilizer like compost or manure.
Be patient for the first year. Peonies spend this time developing their root and foliage systems, so they rarely bloom until their second season.
If your peony develops buds that fail to open, look at them carefully. If there were late frosts in your area, the buds may have gotten frostbitten and they'll look pinched and dried out. If the buds have opened up a bit but are streaked, they may be suffering from a thrip infestation.
Combat thrips by introducing natural predators like ladybugs to your garden, or by spraying your plants with insecticidal soap, which you can buy at nurseries and home improvement stores.
Divide your older peony plants. Sometimes a peony that’s been growing well for several years will suddenly flower less or stop flowering altogether. If this happens, wait until fall and then dig the plant up very carefully.
Cut the clump at the base of the plant into several sections with a sharp knife, being careful to get three to five of the eyes into each section. Then you can either replant the sections immediately or give some away to friends who'd like to grow their own spectacular peonies.