Poison hemlock Conium maculatum L.
Family: Apiaceae (Parsley family)
Life cycle: Biennial
Native status: Introduced
Habitat: Pastures, roadsides, no-till fields
General description: Basal rosette during first year and then erect flower stalk 6 to 8 ft tall. Leaves are triangular, finely divided and glabrous. Umbels up to 4 in wide with white flowers. Rosettes resume growth in March/April.
Key ID traits: Leaves are triangular in shape and pinnately lobed up to 18" long. Hairless stem with purple spots, often covered with a waxy bloom.
Similar species: Wild carrot is found in similar habitats, but leaves of wild carrot are pubescent, linear in shape, and more finely divided than poison hemlock. Poison hemlock is a much larger plant than wild carrot. Water hemlock has a spotted stem like poison hemlock, but is a perennial that produces a cluster of fleshy tubers at crown, and the leaflets are not finely divided like poison hemlock.
Miscellaneous: Poison hemlock contains the toxin coniine which disrupts the central nervous system. Coniine has a structure similar to nicotine. Poison hemlock was commonly used to poison condemned prisoners in ancient Greece, and is believed to be the poison used to kill Socrates.