A frequent problem on peonies is failure of flower buds to open in spring. Typically, the flower buds develop to about the size of a pea and then fail to develop further. There are several possible causes. Following are the most common reasons why peony buds may fail to open.
Botrytis blight
Botrytis blight also called gray mold is a common fungal disease of many plants including peonies. It commonly affects the new shoots and foliage of peonies (see Botrytis Blight of Peony herein) but can also affect young flower buds. The young buds turn brown and fail to open. Once affected, a flower bud can not be saved. To address the disease in subsequent years follow the practices outlined in Botrytis Blight of Peony.
Cold temperatures in early spring.
When the young peony flower buds are subjected to cold temperatures in early spring as they begin to develop growth may stop when they are about the size of a pea. They may take on a reddish appearance but do not become brown and papery as in botrytis blight. Nor do they develop the gray mold characteristic of botrytis blight. Later in the season, however, the buds will brown and fall off. If possible, relocate peonies to a location where they are less subject to late spring freezes or protect plants when freezing temperatures are forecast.
Too much shade, lack of proper fertilization, or drought
Anything that stresses the plant could result in bud blast. This can include too much shade – peonies prefer full sun, lack of adequate fertilization in poor soil, or a period of drought when the plants are making active growth and buds are developing in spring. Provide the plants with adequate sun, fertilizer and moisture, especially in early spring when they are making active growth.
Plants are too young or have been recently divided
Newly planted or divided and transplanted peonies may take a year or two to become established before they flower normally. Be patient and give the plants good care. | 
