Its green foliage may show up before most other plants leaf out. Livestock tug at the tender leaves and pull roots from the soil which are still soft from late winter rains. The combinations of foliage and roots in considerable quantity can be fatal. As a preventative, pull water hemlock plants from the soil during the summer when they can readily be found and destroy them. Plants usually are not numerous in an area.
Flowers are showy, umbrella-like clusters and appear in late summer.
The poison is a volatile alkaloid, coniine, found in the foliage all season and in the seeds in late summer. Most livestock poisoning comes in the spring from eating fresh foliage. 18 Mayapple, bloodroot, pokeweed, nightshade and hellebore are other alkaloidal plants. They are rarely eaten except when animals are starving for better feed. Deaths from alkaloidal plants usually result from severe digestive disturbances, pain and nervous symptoms.