From left, all parts of a hosta plant — leaves, flowers, and roots — are toxic to dogs and cats. Right, any plant in the chrysanthemum family, such as asters, mint, dahlias, carnations, lilies, marigolds, and more, is toxic to your dog. All parts of the chrysanthemum are highly poisonous: leaves, stems, flowers, and sap because they contain pyrethrins. If your pet may have ingested chrysanthemum, get them to the vet immediately.