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Poison Hemlock (Conium maculatum)      

One of the distinguishing characteristics of Poison Hemlock is the purplish spots on the stems.
One of the distinguishing characteristics of Poison Hemlock is the purplish spots on the stems.

Poison Hemlock is noted for its toxicity. It is a herbaceous biennial plant which grows between 1.5-2.5 m tall, with a smooth green stem, usually spotted or streaked with red or purple on the lower half of the stem. The leaves are finely divided and lacy, overall triangular in shape, up to 50 cm long and 40 cm broad. The flowers are small, white, clustered in umbels up to 10-15 cm across. The plant is often mistaken for fennel, parsley or wild carrot although the characteristic stem hairs of the wild carrots are missing. The Poison Hemlock root is fleshy, white and often unbranched and can be mistaken for parsnip. When crushed, the leaves and root emit a rank, unpleasant odour often compared to that of a mouse or parsnips.

Poison Hemlock contains the alkaloids Coniine, N-methylconiine, conhydrine, pseudoconhydrine, g-coniceïne and Atropine . The most important and toxic of these is Coniine. Coniine is a neurotoxin, which disrupts the workings of the central nervous system and is toxic to people and all classes of livestock.

Poison Hemlock has been introduced and naturalised in many other areas, including much of Asia, North America and Australia. Poison hemlock is often found on poorly drained soils, particularly near streams, ditches, and other surface water. (From Wikipedia)

Poison Hemlock rosette.
Poison Hemlock rosette.
Photo courtesy of Ada County Weed Control.

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