Eastern Forest Threat Center - Poison Hemlock

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Poison hemlock flowers

Poison hemlock flowers

John Cardina, Ohio State University, Bugwood.org

Poison Hemlock
Conium maculatum

Poison hemlock is native to Europe. It was introduced into North America in the 1800s as a garden or ornamental plant.

Keywords: Apiaceae, biennial, herb, toxic; Common names: cigue maculae, deadly hemlock, poison parsley, cigue tachetee, poison fool's parsley, spotted hemlock

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Threat Description

Poison hemlock is a biennial herb in the carrot family that grows 3 to 8 ft. tall. It has a thick, white taproot that may easily be mistaken for wild parsnips. Stems are stout, hollow, ridged, and purple-spotted. Leaves are shiny green, 3 to 4 times pinnately compound, and clasp the stem at the obvious nodes. Crushed foliage and roots have a disagreeable, parsnip-like odor. Flowers appearing in early summer are small, white, and borne in umbrella-shaped clusters about 3 in. across. Poison hemlock reproduces from seeds that are ridged and flattened, with 2 seeds borne together. It grows on dry to moist soils and is often found near roadsides, field borders, hiking trails, railroad tracks, stream banks, irrigation ditches, waste areas, riparian woodlands, and open floodplains of rivers and streams. It may act as a pioneer species quickly colonizing disturbed sites and displacing natives during early successional areas. All plant parts are poisonous; however, the seeds contain the highest concentration of poison. Human deaths have occurred from harvesting and consuming the roots as wild carrots or parsnips.