What is peony wilt?
Peony wilt is an infection of the leaves and stems of peonies and tree peonies by the fungus Botrytis paeoniae, which is closely related to the grey mould pathogen Botrytis cinerea. This disease generally appears in spring or early summer when the shoots of affected herbaceous paeonies wilt and turn brown for no apparent reason. This fungus only attacks Paeonia spp.