Abstract
Western waterhemlock (xCicuta douglasii) is the most poisonous plant in North America — a piece of root no larger than a walnut can kill a mature cow. Every part of the plant is toxic. To help farmers, ranchers and other landowners avoid the deadly plant, this publication provides an overview of it, including descriptions and color photographs to help identify the plant, which grows in wet places along streams, irrigation ditches and sloughs in the western United States and Canada. It also provides management strategies, including herbicides and careful land-clearing practices, and some safety advice because its toxicity transfers on contact so readily.