Conium maculatum L.

by Ryan Calvert, Native Plants of Arizona 2004
Common names: P oison hemlock. (1)
Family: Apiaceae. (1)
Synonymy: Coriandrum maculatum (L.) Roth, cicuta maculata lam., conium croaticum, cicuta major Lam., cicuta officinalis Crantz, cicuta vulgaris Delarbre, conium cicuta, conium divaricatum conium leiocarpum, conium maculosum, coriandrum cicuta Crantz, and selinum conium. (4)
Etymology: Conium is derived from the Greek word Konas , which means to whirl about, because the plant causes vertigo and death when ingested. Maculatum is a Latin Word meaning spotted and refers to purple splotches on the leave petioles and the stems. (3)

Growth form: Erect. (2)
Roots: Long, white, fleshy, tap-root that is almost always unbranched (4).
Stem: Erect, branching, without hairs, ridged, hollow except at the nodes, and distinctly purple-spotted.
Leaves: Leaves are broadly ovate in outline, 1-3 dm long, 3-4 times pinnately compound with sheathing petioles. (4)
Inflorescence/flowers: Large (1.5-2.5 inches), white flowers (compound umbels) are each made of a cluster of smaller flowers. The stalks of the individual flowers arise from one point. (1)
Fruit : Small, ridged, smooth, 1/8 inch long, broad, and compressed laterally. Reproduces solely by seeds. Seeds often drop next to the parent plant and regenerate, forming numerous leafy rosettes that form dense colonies of plants. The seeds are not well developed for long range dispersal so the plant spreads seeds primarily by water, birds and rodents (3)
Similar species : Daucus carota (Wild carrot) appears very similar, but the flowers of wild carrot are generally larger and more 'flat-topped' than those of poison hemlock. Cicuta maculata (water hemlock) also appears similar to the poison hemlock except poison hemlock has twice pinnately compound leaves whereas water hemlock's leaves are only once pinnately compound. (6)


Life history: Herbaceous Biennial. (2)
Native/introduced: Eurasian. Introduced to the US as a cultivated ornamental.
Photosynthetic pathway: C3. (7)
Phenology: Poison hemlock has small but attractive white flowers, arranged in umbrella-like clusters, which open in the early summer. The seeds ripen in August and September. (4)
Distribution: Originally from Europe , poison hemlock adapted to North America and Asia . Now it is found worldwide, typically below 5000 ft in temperate climates. along roadsides, edges of cultivated fields, railroad tracks, irrigation ditches, stream banks, and in waste areas. (5)

Conuim Maculatum produces a poison called coniine, therefore, all parts of the plant are extremely poisonous (especially the seeds and young leaves) (5). The Greeks used poison hemlock to make a poisonous drink, used to execute political prisoners. American Indians also used hemlock to poison the tips of their arrows. They also used poison hemlock medicinally as a treatment for ulcers, tumors, and gout. (4)


1. USDA, NRCS. 2004. The PLANTS Database, Version 3.5 ( . National Plant Data Center , Baton Rouge , LA 70874-4490 USA .

2. Retrieved [ November, 4, 2004 ], from the Integrated Taxonomic Information System on-line database, < >.

3. Grieve M. A Modern Herbal : The Medicinal, Culinary, Cosmetic and Economic Properties, Cultivation and Folk-Lore of Herbs, Grasses, Fungi, Shrubs & Trees with their Modern Scientific Uses. New York . Dover Publications Inc. 1995.

4. Moser, L; D. Crisp. San Francisco Peaks Weed Management Area fact sheet on Conium maculatum . Coconino National Forest .

5. INCHEM. 16 September 2004 . International Program on Chemical Safety. 5 December 2004 . <>

6. Cornell University Poisonous Plants Informational Database. 29 October 2003 . Cornell College of Veterinary Medicine. 8 December 2004 . <>.

7. Rangeland Ecosystems and Plants. January 2000. The Department of Plant Sciences at the University of Saskatchewan . 8 December 2004.<>.