It usually grows for 2 years, but in favorable locations it may be a perennial. Roots of poison-hemlock may easily be mistaken for wild parsnips. Poison-hemlock grows along fence lines, in irrigation ditches, and in other moist, waste places. It may be 2 to 3 meters tall. The hollow stem usually is marked with small purple spots.
Leaves are delicate, like parsley, and it has a white taproot.
Poison-hemlock is a biennial in the parsnip or wild carrot family. Leaves are especially poisonous in the spring, up to the time the plant flowers. Fresh leaves are unpalatable, so livestock seldom eat hemlock when other feed is available. The toxic compounds are coniine, g -coniceine, and related piperidine alkaloids. People may be poisoned by eating any part of a hemlock plant.