Poinsettia Dangerous winter holiday plants for humans and pets Dangerous Winter Holiday Plants for Pets PetMD poinsettias, mistletoe, holly, amaryllis, and lilies exposure to the cold Poinsettias and Mistletoe contains toxic to pets plants toxic holiday plants to pets Dangerous Winter Holiday Plants for Pets poinsettia PetMD harmful to pets they contain holiday plants traditional holiday plants petMD. plants PetMD poinsettias are nontoxic