What's eating my peony?

Peonies are troubled by ants (harmless — they harvest nectar from buds), botrytis blight in wet springs that blackens stems, aphids on new shoots, and thrips inside flowers. Deer occasionally browse stems. Botrytis (Botrytis paeoniae) is the most damaging true threat, capable of killing stems at ground level and preventing flowering entirely in cool, wet conditions.

Stems wilt and collapse at the base with a brown, water-soaked rot; flower buds turn brown and fail to open; grey mould may be visible in humid conditions; young shoots may blacken as they emerge. Cut out and bin (do not compost) infected stems well below the rot; improve air circulation; avoid mulching over the crown; apply copper-based fungicide in spring as shoots emerge.

Soft colonies on emerging shoots and around buds cause distorted, sticky growth; ants are often present farming the aphid colonies (the ants themselves do not damage peonies). Spray with insecticidal soap; knock off with water; introduce natural predators; colonies usually disappear once cooler summer weather arrives.

Inside flower petals, thrips cause silvery streaking, browning of petal edges, and distorted, short-lived blooms; damage is most obvious on pale-coloured varieties. Remove spent flowers promptly; apply spinosad spray at dusk; use sticky traps to monitor; avoid excess nitrogen which produces softer tissue that attracts thrips.