Peonies are toxic to dogs. The poisonous compound in peonies is called paeonol , which is mainly concentrated in the roots but is also present in the petals, stems, and bark. If a dog ingests any part of the peony plant, it can cause gastrointestinal symptoms such as vomiting, diarrhea, nausea, abdominal pain, and lethargy. The toxicity level depends on the amount ingested and the dog's health condition. Immediate veterinary care is recommended if ingestion occurs to manage symptoms and prevent complications.