Socrates in Sonoma

Conium maculatum L.

By SCMG Sue Ridgeway

What do Socrates and the citizens of Sonoma County have in common?  Socrates enjoyed living in a glorious, Mediterranean climate, in a democratic society, and like us, he valued the importance of establishing friendships, and building community.   

Unfortunately, not all Athenians appreciated his views, and for his impiety, Socrates was sentenced to a “humane” death by poisoning (thankfully a practice we don’t share).  He was forced to drink a toxic brew made, allegedly, from an infusion of the plant Conium maculatum L. or, as it is more commonly known, poison Hemlock.

Poison Hemlock, also referred to as carrot fern, poison parsley, or spotted hemlock, is a member of the Apiaceae  - or carrot - family, but unlike Bugs Bunny’s favorite food, every part of Conium maculatum L. is poisonous.  Unfortunately, poison Hemlock has invaded Sonoma County, and its presence can be considered a clear and present danger to the unwary.

According to the California Invasive Plant Council, Poison hemlock is native to Europe, North Africa, and Asia, and was brought to the United States as a garden plant sometime in the 1800s.  It has spread throughout California, surviving at elevations up to 3,300 feet.  In many California counties, it can be seen in dense patches along roadsides and fields.

Poison Hemlock only propagates by seed; it is dispersed by animals, birds, people, tractors and tires.  It prefers to grow in disturbed, shady areas with moist soils.  However, it is an opportunist, and the herbaceous plants can be found growing in riparian forests, flood plains, and in dry open areas. The species is now frequently seen gracing Sonoma County creeks, trails, roadsides, and potentially, our yards and gardens.  Everyone should learn to identify Conium maculatum L., and familiarize themselves with the problems it can cause both man and beast.

What are the distinctive features of poison Hemlock?  It is considered a biennial, so the first year’s growth is usually ground level rosettes.  However, during its second year, at maturity in July and August, it attains heights of from one to ten feet tall – growing on tall, hollow, ribbed, green stems with reddish-purple streaks or spots near the bottom.

Conium maculatum L blooms from April through July.  It has small, white, flowers, arranged in umbrella like clusters supported by branching stalks.  It has parsley (or lacy fern) like leaves.  When crushed, the leaves and roots have a distinctive rank – or mousy – odor that some compare to parsnips.
 
C. maculatum L. is poisonous; the entire plant contains toxic alkaloids; the most dangerous of these is coniine, a neurotoxin. Coniine causes ascending, muscular paralysis, and ingestion of any part of the plant, by humans or domestic animals, in any quantity, can result in respiratory failure and death.  

For an adult, eating approximately six to eight fresh leaves, or a smaller dose of the seeds or root, may be fatal.  If the acute poisoning is recognized in time, death can be prevented by artificial ventilation until the muscular paralysis wears off in approximately 48–72 hours. If pregnant livestock graze on the plant, consuming it in small doses that do not kill, the chronic, alkaloid poisoning can result in deformities of developing embryos.  Additionally, poison Hemlock alkaloids can enter the human food chain through the consumption of contaminated milk and birds.

Once ingested, there is no specific antidote for these alkaloids.  Prevention, eradication, and public awareness are the only ways to deal with the potential danger posed by this invasion of the poison Hemlock plant, the bane of Socrates.

If you are interested in learning more about poison Hemlock, you can read the UC Davis Agriculture and Natural Resources document on livestock poisoning plants, visit the UC  Davis-IPM  website, the California Invasive Plant Council website,  the USDA Natural Resources Conservation Service – Plants Profile, or the International  Programme on Chemical Safety – INCHEM website.  

To view photo documentation of Conium maculatum L. from seed to mature plant, visit Forestry Images, a joint project of the Center for Invasive Species and Ecosystem Health, USDA Forest Service and International Society of Arboriculture.