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Conium
Conium maculatum
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Apiales
Family:	Apiaceae
Subfamily:	Apioideae
Genus:	Conium L.
Species
Conium chaerophylloides (Thunb.) Sond. Conium maculatum L.

Poison hemlock redirects here. For other uses of "hemlock", see Hemlock.

Conium (/kəʊ'naiəm/) is a genus of two species of highly poisonous perennial herbaceous flowering plants in the family Apiaceae, native to Europe and the Mediterranean region (C. maculatum), and to southern Africa (C. chaerophylloides).

By far the most familiar species is Conium maculatum (Hemlock or Poison Hemlock), the most common of several species of hemlock noted for their toxicity. It is a herbaceous biennial plant which grows between 1.5–2.5 m tall, with a smooth green stem, usually spotted or streaked with red or purple on the lower half of the stem. The leaves are finely divided and lacy, overall triangular in shape, up to 50 cm long and 40 cm broad. The flowers are small, white, clustered in umbels up to 10–15 cm across. The plant is often mistaken for fennel, parsley or wild carrot although the characteristic stem hairs of the wild carrots are missing. The Conium root is fleshy, white and often unbranched and can be mistaken for parsnip. When crushed, the leaves and root emit a rank, unpleasant odour often compared to that of parsnips.

Name

Hemlock is known by several common names. As well as the American "Poison hemlock" and the Irish "Devil's porridge", there are also Beaver Poison, Herb Bennet (not to be confused with the geranium of that name), Musquash Root, Poison Parsley, Spotted Corobane and Spotted Hemlock. The seeds are sometimes called Kecksies or Kex.

Distribution

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Conium maculatum is native in temperate regions of Europe, as well as North Africa.

Conium maculatum has been introduced and naturalised in many other areas, including Asia, North America and Australia. It is often found on poorly drained soils, particularly near streams, ditches, and other surface water. It is considered an invasive in twelve US states.

Ecology

Conium grows in damp areas.

It is used as a food plant by the larvae of some Lepidoptera species including Silver-ground Carpet.

Life cycle

Poison hemlock flourishes in the spring, when most other forage is gone. All plant parts are poisonous but once the plant is dried, the poison is greatly reduced, although not gone completely. Hemlock is also known as "poison parsley" or "spotted parsley".

Similar species

In the Mountain West of North America, poison hemlock has become well established and invasive, and can be found in remote mountain areas anywhere water is present or soils are persistently moist. It is often found growing in the same habitat and side by side with Osha and Lomatium species, useful medicinal relatives in the Parsley family which Hemlock closely resembles, and can be very difficult to distinguish from Lomatium (an important historical food plant of Native Americans known as Biscuit Root).

Hemlock's distinguishing characteristics are that it requires a more consistent supply of water than Lomatium or Osha, and Lomatium species tend to prefer dry rocky soils devoid of organic material. Lomatium roots have a delicate rice-like odor, unlike the musty odor of Hemlock, with finely divided, hairlike leaves in most Lomatium species. Lomatium species tend to produce yellow flowers, but some species are white flowered and closely resemble Poison Hemlock. If the plant is growing on a hillside in dry, mineral soil far away from a source of water and has umbells of yellow flowers, its likely a Lomatium. If the plant is growing in an area near water in consistently moist soil, is tall (0.75-2m), has purple splotches on the main stem, and is heavily branched with small umbels of white flowers, it is probably Hemlock and should be avoided.

Osha does not do well in overly moist soils since it is a species dependent on mycorrhizal fungi to survive, but there are areas where Osha and Poison Hemlock can be found only a few feet from each other. Poison Hemlock lacks the "spicy celery" odor of Osha, and is easily distinguished from it due to the absence of hairlike dead leaf material present on the root crown of Osha roots. Poison Hemlock roots in many cases have no discernible odor, and are typically heavily branched rather than carrot-like, but this is not always the case. The plants themselves smell musty or "mousy", and in most instances will have purple blotches or shading on the lower stem of the plant if the plant is fairly mature, but again, this is not always the case.

A useful trick to determine whether a plant is poison hemlock rather than fennel, which it resembles, is to crush some leaves and smell the result. Fennel smells like anise or liquorice, whereas the smell of poison hemlock is often described as mouse-like or musty. Considering the high toxicity of poison hemlock, if the plant cannot be identified it must be discarded. Coniine can be absorbed through the skin, and it is well advised to wash your hands immediately after handling this plant and avoid touching your eyes or mouth if you have recently handled or come into contact with Poison Hemlock, or if you have crushed the leaves of this plant in your hand to perform a "smell test".

Poison hemlock is sometimes confused with water hemlocks in the related genus Cicuta, but are readily distinguished by the less finely divided leaves of the latter; the leaf veins of poison hemlock also run through the tips of the teeth, but those of the water hemlock run through the notches in between the teeth. The poison hemlock's root is long, white, and fleshy and is usually stringy and heavily branched, but can be carrot-like and unbranched in younger specimens of Conium. Water hemlock's roots are made up of several tubers, and are typically chambered, and exude a yellow, rank, highly toxic sap that contains cicutoxin.

These plants all have white flowers in large compound umbels. Therefore, these plants are confused with each other; the water parsnip, (swamp parsnip, sium suave) and the western water hemlock, (Cicuta douglasii, poison hemlock) or the spotted water hemlock (cicuta maculata, spotted water hemlock, spotted parsley, spotted cowbane). Water parsnip and water hemlock both have cluster of small white flowers shaped like umbrellas, and both have the same habitat near the shore line of lakes, and rivers. Water parsnip has leaves only once compound, and water hemlock has leaves which are three times compound. Water hemlock has a large swelling at the stem base. All water hemlock is highly poisonous. Water parsnip is not poisonous. The water hemlock has bracts at the base of each small flower cluster, not at the base of the main flower head. The Water parsnip has small bracts at the base of flowers and main flower head as well. The Yarrow, (Common Yarrow, Gordaldo, Nosebleed plant, Old Man's Pepper, Sanguinary, Milfoil, Soldier's Woundwort, Thousand-leaf (as its binomial name affirms), Thousand-seal or Achillea millefolium) also has many small white flowers in a cluster. However the yarrow has feathery looking leaves which are pinnately separated into small narrow segments. The cow parsnip (heracleum lanatum, Heracleum maxinium Indian Celery or Pushki, and Heracleum sphondylium, hogweed) is also confused in this group with similar flower groupings. However, the cow parsnip has large, broad leaves, and an unpleasant odour.

Biochemistry

Poison

Conium contains the piperidine alkaloids coniine, N-methylconiine, conhydrine, pseudoconhydrine and gamma coniceine (or g-coniceïne), which is the precursor of the other hemlock alkaloids.

The most important and toxic of these is coniine, which has a chemical structure similar to nicotine. Coniine is a neurotoxin, which disrupts the workings of the central nervous system and is toxic to humans and all classes of livestock. Coniine causes death by blocking the neuromuscular junction in a manner similar to curare; this results in an ascending muscular paralysis with eventual paralysis of the respiratory muscles which results in death due to lack of oxygen to the heart and brain. Death can easily be prevented by artificial ventilation until the effects have worn off 48-72 hours later. Ingestion of Poison Hemlock in any quantity can result in respiratory collapse and death. For an adult the ingestion of more than 100 mg of coniine (approximately 6 to 8 fresh leaves, or a smaller dose of the seeds or root) may result in fatality.

Socrates

In ancient Greece, hemlock was used to poison condemned prisoners. The most famous victim of hemlock poisoning is the philosopher Socrates. After being condemned to death for impiety in 399 BC, Socrates was given a potent solution of the hemlock plant. Plato described Socrates' death in the Phaedo :

"The man … laid his hands on him and after a while examined his feet and legs, then pinched his foot hard and asked if he felt it. He said ‘No’; then after that, his thighs; and passing upwards in this way he showed us that he was growing cold and rigid. And then again he touched him and said that when it reached his heart, he would be gone. The chill had now reached the region about the groin, and uncovering his face, which had been covered, he said — and these were his last words — 'Crito, we owe a cock to Asclepius. Pay it and do not neglect it.' 'That,' said Crito, 'shall be done; but see if you have anything else to say.' To this question he made no reply, but after a little while he moved; the attendant uncovered him; his eyes were fixed. And Crito when he saw it, closed his mouth and eyes."

Although many have questioned whether this is a factual account, careful attention to Plato's words, modern and ancient medicine, and other ancient Greek sources point to the above account being consistent with Conium poisoning.

Sometimes the characteristic red spots found on the stem and branches are referred to as "the blood of Socrates" in reference to his death.

Another well known person, John Kane, also died of conium poisoning. A well-known rock band during the Greek junta was called Socrates Drank the Conium.

Effects on non-human animals

C. maculatum is poisonous to animals. In a short time the alkaloids produce a potentially fatal neuromuscular blockage when the respiratory muscles are affected. Acute toxicity, if not lethal, may resolve in the spontaneous recovery of the affected animals provided further exposure is avoided. It has been observed that poisoned animals tend to return to feed on this plant. Chronic toxicity affects only pregnant animals. When they are poisoned by C. maculatum during the fetuses organ formation period, the offspring is born with malformations, mainly palatoschisis and multiple congenital contractures (MCC; frequently described as arthrogryposis). Chronic toxicity is irreversible and although MCC can be surgically corrected in some cases, most of the malformed animals are lost. Since no specific antidote is available, prevention is the only way to deal with the production losses caused by the plant. Control with herbicides and grazing with less susceptible animals (such as sheep) have been suggested. C. maculatum alkaloids can enter the human food chain via milk and fowl. Such losses may be underestimated, at least in some regions, because of the difficulty in associating malformations with the much earlier maternal poisoning.

Medicinal uses

Poison hemlock has been used as a sedative and for its antispasmodic properties. It was also used by Greek and Persian physicians for a variety of problems, such as arthritis. It wasn't always effective, however, as the difference between a therapeutic and a toxic amount is very slight. Overdoses can produce paralysis and loss of speech being followed by depression of the respiratory function and then death.

References

1. National park Service map retrieved 14 January 2009
2. "Water hemlock (Cicuta spp.)". Natural Standard, The Authority on Integrative Medicine. Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
3. "Water Hemlock (Cicuta douglasii)". Field Guide to Noxious and Other Selected Weeds of British Columbia. Ministry of Agriculture and Lands Government of British Columbia. Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
4. "Cicuta maculata". Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
5. "Traditional Plant Foods of Canadian Indigenous Peoples By Harriet V Kuhnlein, Nancy J." Google books. Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
6. "Western Water Hemlock - Agriculture - Government of Saskatchewan". Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
7. "Water Parsnip - Agriculture - Government of Saskatchewan". Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
8. "Yarrow Achillea millefolium". Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
9. "Heracleum lanatum". University of Saskatchewan. Retrieved 2008-08-03. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
10. Reynolds T. (2005). Hemlock alkaloids from Socrates to poison aloes. Phytochemistry.66:1399-1406.
11. Vetter J. (2004).Food Chem Toxicol.42:1373-1382.
12. Brooks, Daniel E. (2008-11-07). "Plant Poisoning, Hemlock". eMedicine. Retrieved 2009-02-20. {{cite news}}: Cite has empty unknown parameter: |coauthors= (help)
13. Vetter J. (2004).Food Chem Toxicol.42:1373-1382.
14. Edible and Medicinal plants of the West, Gregory L. Tilford, ISBN 0-87842-359-1.
15. IPCS (International Programme on Chemical Safety)
16. Plato, Euthyphro, Apology, Crito, Phaedo
17. Plato, Phaedo 117e–118a, trans. Loeb Classical Library, Harvard University Press, Cambridge, Mass., 1990 edition, pp. 401–3.
18. Bloch, Enid (2001). "Hemlock Poisoning and the Death of Socrates: Did Plato Tell the Truth?". Journal of the International Plato Society (1). {{cite journal}}: Unknown parameter |month= ignored (help) A version of this article was also printed in Thomas C. Brickhouse (Editor), Nicholas D. Smith (Editor) (2001). The Trial and Execution of Socrates: Sources and Controversies. New York: Oxford University Press. ISBN 978-0195119800. {{cite book}}: |author= has generic name (help)
19. SAIN Invasive Plant Pests Resource Collection for Conium maculatum (this text is adapted from Public Domain material at the National Biological information Infrastructure website, retrieved 14 January 2009

External links

• Germplasm Resources Information Network: Conium
• Flora Europaea: Conium
• Edible and Medicinal plants of the West, Gregory L. Tilford, ISBN 0-87842-359-1

• Apiaceae
• Poisonous plants
• Flora of California