Cicuta Douglasii

Western Water Hemlock

Paul Smith

Botany 113
Spring Quarter 2015

C. Douglasii is an herbaceous perennial growing from a half to two meters in height in wet habitat from sea level to mid-elevations. The base of the stem is thickened, hollow and has several chambers formed by thick membranes at right angles to the stem axis.

Leaves are pinnately compound, with lanceolate to oblong leaflets (3 to 10 cm wide by 5 to 35 cm long) having pinnate venation. Both basal and cauline leaves are present.


Leaflet margins are serrate, and provide a key characteristic for identification: leaflet veins intersect margins at the base of serrations rather than serration tips (see photo).


Flowers are small, white to greenish in color with a floral formula as follows: *5,5,5,2 (ovaries connate and inferior). Fruit is a schizocarp split into two mericarps, each about 2 to 4 mm long. Flowers are born in a compound umbel that – unlike most members of this family – most often lack a basal involucre of bracts.


Cicuta douglasii is widespread, but not nearly as common as Conium maculatum (Poison Hemlock) in our area.


Water Hemlock species are violently toxic, containing the neurotoxin cicutoxin. This toxin blocks the inhibitory neurotransmitter gamma amino-butyric acid (GABA), similar to strychnine. Poisoning results in convulsions, vomiting, pupil dilation and other effects. Cause of death is usually suffocation when diaphragm muscles spasm and the victim cannot inhale. Apiaceae also contains many food plants: poisoning often occurs when Cicuta is mistaken for an edible herb. One anecdotal case involved a child who used a whistle made from the hollow stem base, reported to be the most toxic part of the plant.


Treatment includes anticonvulsants and hydration. Ironically, Conium maculatum (Poison Hemlock) causes death through paralysis of voluntary muscles, which would tend to counteract cicutoxin. However, given the quick onset of cicutoxin and uncertainty of dose, it does not offer a practical way to offset the poisoning.


Ethnobotanical uses include a treatment for leukemia and possibly other cancers much as the toxin from Taxus brevifolia has been used in the treatment of breast cancer. In addition, Native Americans may have used it as a poultice (given the nature of the poison, there are no doubt better solutions available today).


References:


Photo credit: 2006, G. D. Carr. (Permission granted for educational use of image on Burke website. See Knote & Giblin reference.)


United States Department of Agriculture. (2006) Water hemlock (Cicuta douglasii). Retrieved from: http://www.ars.usda.gov/Services/docs.htm?docid=9996


Knote, D. and Giblin, D. (2015). Cicuta Douglasii - Western Water-Wemlock, Douglas' Water-Hemlock. Burke Museum of Natural History and Culture. Retrieved from:

http://biology.burke.washington.edu/herbarium/imagecollection.php?Genus=Cicuta&Species=douglasii


Takao Konoshima and Kuo-Hsiung Lee. (1986). Antitumor agents, 85. Cicutoxin, an antileukemic principle from cicuta maculata, and the cytotoxicity of the related derivatives. Journal of Natural Products vol 49, No 6 pp. 1117–1121 Nov–Dec 1986. Retrieved from http://pubs.acs.org/doi/pdf/10.1021/np50048a028


Hitchcock, C. L. and Cronquist, A. (1973). Flora of the Pacific Northwest: An Illustrated Manual. Seattle and London: University of Washington Press.


Pojar, J. and Mackinnon, A. (1994). Plants of the Pacific Northwest Coast: Washington, Oregon, British Columbia & Alaska. China: Lone Pine Publishing.