Water Hemlock, a poisonous perennial herb that grows near water from southern Canada to the Gulf of Mexico. It grows to be six feet (1.8 m) tall and bears flat-topped clusters of tiny white flowers. The large leaves are composed of numerous toothed leaflets. All parts of the water hemlock, particularly the roots, are poisonous if ingested. Even a small piece of the root can be deadly.
Water hemlock is Cicuta maculata of the parsley family, Umbelliferae.