General: plant height: 50-300 cm. Growth habit: erect biennial from stout, single, white taproot. Stems: much branched, purple-spotted, hollow.
Leaves: feathery, finely divided 3-4 times into small segments, the blades of the larger leaves commonly 15-30 cm long. Basal and lower leaves are stalked and sheathing at base, upper leaves stalkless.
Flowers: white, tiny, in numerous compound umbels, with 5 notched petals about 1.5 mm long. Rays slender, almost equal, 2.5-4 cm long. Mature flower stalks 4-6 mm long. Primary and secondary bracts short and narrow.
Fruits: flattened, 2-2.5 mm long, ovoid and curved, with prominent, wavy ribs.
Roadside ditches and other moist disturbed sites in s. and w. parts of MT. Native to Eurasia, now established as a weed over most of N. America.
All parts of poison hemlock are highly toxic and may result in death if eaten. The leaves can be mistaken for parsley and the seeds mistaken for anise. Young foliage and unripe seeds have the highest alkaloid content. The famous "Cup of hemlock" were once used by early Greeks for capital punishment. The philosopher Socrates was sentenced to death and died in 399 BC after drinking hemlock juice. The toxic principle is the alkaloid coniine among others. In poisonous doses it produces complete paralysis with loss of speech, the respiratory function is at first depressed and ultimately ceases altogether and death results from asphyxia. The mind remains unaffected to the last. In the account of the death of Socrates, reference is made to loss of sensation as one of the prominent symptoms of his poisoning, but the dominant action is on the motor system. In man, 3 mg of coniine is said to have produced symptoms, but 15 mg have been tolerated without discomfort. Perhaps 30-60 mg is dangerous and death may occur with doses greater than 100 mg. It has been reported that a lethal dose may be 6 to 8 fresh leaves. Symptoms include irritation of the mucous membranes, nausea, vomiting and profuse salivation. Abdominal pain is usually minimal and diarrhea is infrequent. Drowsiness, paresthesiae, ataxia and gradually increasing muscular weakness followed by ascending paralysis leads to respiratory failure. Treatment includes administration of activated charcoal.
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