Poison Gardens – Water Hemlock

Water hemlock (Cicuta douglasii) is a flowering perennial herbaceous plant in the carrot family (Apiaceae). The United States Department of Agriculture (USDA) considers water hemlock the most poisonous plants in the Western United States, with a range from Alaska to California. Several other plants may be mistaken for water hemlock, including poison hemlock (Conium maculatum – used in the poisoning death of Socrates), wild parsnips, and other herbs or perennial plants).

Water hemlock. Photo by Barry Breckling, used under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 (CC BY-NC-SA 3.0) license.

The heavy scented plant grows up to 8 feet tall (2.5 meters), with a sturdy, hollow stalk; small white flowers in terminal compound umbels; leaves decompounded (side veins lead to notches, not to tips, at the outer margins); poisonous roots; and slightly flattened fruits.  The thick rootstalk includes several chambers containing the poisonous compound cicutoxin, which is an unsaturated aliphatic alcohol (although all parts of the plant are poisonous).

 Cicutoxin works on the central nervous system. Symptoms include nervousness, excessive salivation and frothing, muscular twitches, dilation of the pupils, rapid pulse and breathing, tremors, violent convulsions, and death from asphyxiation and cardiovascular collapse. A very small amount can cause death in people, pets, and livestock. Contact a poison control center immediately if symptoms occur.

The plant is found in riparian areas, near stream banks, bogs, and marshy areas. It can be used in a wild or bog landscape, but may not be an appropriate choice for small children, pets, or livestock.