Spotted water hemlock

Cicuta maculata is a species of flowering plant in the carrot family known by several common names, including spotted water hemlock, spotted parsley, spotted cowbane, and the suicide root by the Iroquois. It is native to nearly all of North America, from northern Canada to southern Mexico. This is a rhizomatous perennial herb producing a hollow erect stem to a maximum height between 1 and 1.5 meters. The long leaves are made up of several lance-shaped, pointed, serrated leaflets. Each shiny green leaflet is 2 to 10 centimeters long and the entire leaf may be up to 40 centimeters long. The inflorescence of white flowers is similar in appearance to many other species in the carrot family. It is a compound umbel with a many clusters of flowers. The dry tan-brown fruit is a few millimeters long.

Toxicity
The plant is occasionally mistaken for parsnips, due to its clusters of white tuberous roots; this is an often fatal error, as the Cicuta is extremely poisonous. Indeed, spotted water hemlock is considered to be North America's most toxic plant.[2][3] Cicuta is fatal when swallowed, causing violent and painful convulsions. Though a number of people have died from water hemlock poisoning over the centuries, livestock have long been the worst affected (hence the name "cowbane"), causing death in as little as 15 minutes.,[4][5]
The chief poison is cicutoxin, an unsaturated aliphatic alcohol that is most concentrated in the roots. Upon human consumption, nausea, vomiting, and tremors occur within 30–60 minutes, followed by severe cramps, projectile vomiting, and convulsions. There are occasional long-term effects, like retrograde amnesia.[6] Ingestion of water hemlock in any quantity can result in death or permanent neurological damage of the central nervous system.