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Poison hemlock (Conium maculatum)

Poison hemlock Common Names: Poison-hemlock, deadly hemlock, poison parsley, poison fool?s parsley, cigue maculee, cigue tachetee

Description: All parts of poison hemlock are poisonous.

Habit: Coarse, freely-branched biennial from a stout taproot, 0.5-3 m. tall, with purple-spotted, hollow stem.

Leaves: Large, all cauline, ternate-pinnately dissected, ultimate segments are small.

Stems: 0.5-3m high, stout, erect, branched, glabrous, hollow except at the nodes, have longitudinal lines and purple markings and produce and offensive odor when damaged.

Flowers: Compound umbels numerous, rays sub-equal, 1-4 cm. long; involucre and involucel of several small, lanceolate, bracts or bractlets; calyx teeth obsolete; petals 5, white in color.

Fruit and seeds: Stylopodium depressed-conic; fruit glabrous, broadly ovoid, 2-2.5 mm. long, with prominent, raised, wavy, almost winged ribs.

Habitat: Native to Europe, western Asia and North Africa. Found in roadsides, fields, disturbed places, clearings, banks and bluffs, shores.

Reproduction: Spread by seed dispersal; seeds can adhere to farm machinery, vehicles, agricultural produce, mud and clothing.

Similar species: Giant hogweed (Heracleum mantegazzianum), Cow parsnip (Heracleum maximum).

Monitoring and rapid response: Physical or chemical removal is easy, but complete eradication may be difficult due to a viable seed bank and reintroductions. Management efforts may need to be continued for several years to be effective. Agonopterix alstroemeriana (poison hemlock defoliating moth) is being investigated as a potential biocontrol agent along with Trichoplusia ni, the cabbage looper, and Papulio poluxenes, black swallowtail butterfly. Capable of being infected by multiple viruses, including ring spot virus, carrot thin leaf virus, alfalfa mosaic virus and celery mosaic virus. Care should be taken with handling - plant is toxic.

Credits: The information provided in this factsheet was gathered from the Burke Museum of Natural History and Culture, Great Lakes Aquatic Nonindigenous Species Information System, and the Herbarium at University of Michigan.

Individual species images that appear with a number in a black box are courtesy of the network ( Individual photo author credits may not be included due to the small display size of the images and subsequent difficulty of reading the provided text. All other images appear courtesy of Google (

Common Name:

Poison hemlock

Scientific Name:

Conium maculatum







USDA Symbol: