Peonies are large flowering shrubs that are hardy to cold temperatures but require the right set of conditions to grow and bloom. The plants grow in shrub and tree forms, and can range from 2 feet to 4 feet in height depending on cultivar and pruning. If a peony is not blooming, it may need a better location or set of growing conditions, or it may be due to reckless cutting on behalf of the gardener.
Season and Zone
Peonies are hardy down to U.S. Department of Agriculture Growing Zone 4, but only in certain cultivars, and will grow and bloom successfully through summer up to zone 9. Peonies in colder and warmer zones than this may not thrive or bloom outdoors. La Pivoinerie D’Aoust Peony Nursery recommends only fall plantings for peonies, regardless of growing zone, noting that spring-planting seedlings and tubers have trouble establishing, and may not bloom.
Peonies do best in sunny, quick-draining locations and may not flower if they sit in too much shade. According to the Ohio State University Extension, though, the most likely reason for lack of peony flowering is crowding in the planting site. Give each peony 3 feet of space at planting, then divide and transplant the roots when they outgrow that spacing.
Soil and Nutrition
Peonies need the right type of nutritious soil from the start, as they don’t do well with poor nutrition or immediate transplants. Pick a site that gets complete drainage and add 4 to 5 inches of compost per a 12-inch-deep planting site to guarantee nutrition, drainage and consistent moisture. Give peonies 5-10-10 fertilizer every spring to encourage flowering, and maintain 2 to 3 inches of organic mulch on top of the soil to keep the foundation cool and moist. Peonies that don’t get enough nutrition cannot bloom.
Pruning is important for established peonies, but must be restricted on new peony plants. La Pivoinerie D’Aoust Peony Nursery recommends cutting flowers only after the plants reach three years of age, as cutting earlier depletes the plant’s resources for new growth and blooming, and may restrict the plants from ever bearing flowers. Deadhead the plants during the growing season — pull off faded flowers before they go to seed — to maintain a continuous bloom. At the end of the growing season, cut off all spent foliage and blooms, and allow the peony to go into dormancy.p