Water Hemlock Posted on July 20, 2012 by Axie One of North America’s most poisonous plants, contains “cicutoxin.” Many recorded deaths of people, and apparently it kills a lot of grazing livestock. Can grow to 8 feet tall. Apiaceae family. Native. Water Hemlock, Cowbane, Poison Parsnip (Cicuta) Share this: Click to email a link to a friend (Opens in new window) Email Click to share on Facebook (Opens in new window) Facebook Click to print (Opens in new window) Print Click to share on Pinterest (Opens in new window) Pinterest