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Yellowstone County, Montana
Noxious Weed
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Poison Hemlock
(Conium maculatum L.)

Parsley family - Apiaceae

Poison Hemlock

Photo from Weeds of the West, revised ed.


Growth Habit: Biennial, erect to 10 feet tall.

Leaves: Shiny green, fern-like, finely divided 3 & 4 times. Lower leaves have long stalks clasping the stem. Upper leaves on short stalks. Musty oder.

Stem: Stout, branched, purple-spotted with distinct ridges.

Flower:Numerous umbrella shaped clusters of tiny white flowers without sepals. Clusters supported by stalks whorled at branch terminals.

Roots: Large white taproot.

Seeds: Paired, 1/8th inch long, ribbed, concave, light brown.

Reproduction: Seeds only.

Habitat: Dense stands along stream and ditch banks, field margins, transportation rights-of-way, pastures, meadows and waste places.

Biological Controls: Hemlock moth (Agonopterix alstroemeriana).

Herbicides: Escort and E2.

Caution: All plant parts are poisonous when eaten by livestock or humans.

Produced by Wyoming Weed & Pest Council in cooperation with Sandoz Crop Protection Corp.