Peonies are popular perennial flowers because they are easy to maintain once established in full sunlight and well drained soil. The flowers bloom each year with little attention required, unless your peonies get infected with diseases that causes the plants to turn brown, wilt and die.
Blight is caused various types of fungi that present with different signs. Phytophthora cactorum or Botrytis cinerea both cause browning and discoloration.
According to the University of Minnesota Extension, botrytis blight causes brown blooms and fuzzy-looking gray spots to appear on the leaves and stems.
Phytophthora blight can cause wet rot that destroys the peonies’ crowns and root systems. Signs of phytophthora blight include brown or black spots on the leaves and blossoms.
According to the Royal Horticulture Society, the fungus Botrytis paeoniae can also cause browning of peonies. This type of infection is caused peony wilt.
According to the Royal Horticulture Society and the University of Minnesota, removing the infected plant and surrounding peonies is the only effective course of action to eliminate blight or wilt.