Answer: The hornets are probably competing with the ants for the sweet nectar the plant produces. Bees, wasps and hornets are all considered beneficial insects for their pollinating abilities, so I wouldn't discourage the hornets. There is no scientific evidence that peonies will not bloom without the help of ants, but it's a widespread rumor that's commonly accepted as fact. If some of the flowers turn brown before opening, your plant may have the fungal disease Botrytis. If the buds are failing to mature, your plant may be developing more buds than it can possibly open. Cut off the brown and dried buds and remove them from the garden, to avoid the potential spread of any disease that might be present. If weather is especially humid, watch for signs of mildew or fungus on the leaves and flowers and pinch or cut them off immediately.
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