From the description I think you might be thinking of
hemlock water dropwort, a different plant (but still very poisonous). It sounds like a horrible way to go:
"Symptoms include nausea, vomiting, seizures, hallucinations, ataxia, haemorrhaging of the brain and collapse of the lungs."
Hemlock is found in woodland, disturbed ground and poorly drained soils near bodies of water:
en.m.wikipedia.org
It causes ascending paralysis which eventually affects the breathing muscles. It also sounds pretty unpleasant:
"A short time after ingestion, the alkaloids induce potentially fatal neuromuscular dysfunction due to failure of the respiratory muscles. Acute toxicity, if not lethal, may resolve in spontaneous recovery, provided further exposure is avoided. Death can be prevented by artificial ventilation until the effects have worn off 48–72 hours later. For an adult, the ingestion of more than 100 mg (0.1 gram) of coniine (about six to eight fresh leaves, or a smaller dose of the seeds or root) may be fatal. Narcotic-like effects can be observed as soon as 30 minutes after ingestion of green leaf matter of the plant, with victims falling asleep and unconsciousness gradually deepening until death a few hours later."