Conium maculatum

Conium maculatum is a herbaceous flowering plant that grows to {{Convert|1.5|–|2.5|m|ft|sigfig=1|abbr=off}} tall, exceptionally {{Convert|3.6|m|abbr=on}}.{{cite web |title=Poison Hemlock |url=http://piercecountyweedboard.wsu.edu/poison-hemlock |website=pierecountryweedboard.wsu.edu |publisher=Pierce County Noxious Weed Control Board |access-date=2020-05-12 |archive-date=2021-12-08 |archive-url=https://web.archive.org/web/20211208213811/http://piercecountyweedboard.wsu.edu/poison-hemlock |url-status=dead }} All parts of the plant are hairless (glabrous). Hemlock has a smooth, green, hollow stem, usually spotted or streaked with red or purple. The leaves are two- to four-pinnate, finely divided and lacy, overall triangular in shape, up to {{Convert|50|cm|abbr=off}} long and {{Convert|40|cm|abbr=on}} broad.{{Cite web |url=http://luirig.altervista.org/flora/taxa/index1.php?scientific-name=conium+maculatum |title=Altervista Flora Italiana, Cicuta maggiore, Conium maculatum L. includes photos and European distribution map |access-date=2015-06-13 |archive-date=2015-06-15 |archive-url=https://web.archive.org/web/20150615125243/http://luirig.altervista.org/flora/taxa/index1.php?scientific-name=conium+maculatum |url-status=live }} Hemlock's flower is small and white; they are loosely clustered and each flower has five petals.{{Cite book |last=Holm |first=LeRoy G. |url=https://archive.org/details/worldweedsnatura0000unse |title=World weeds: natural histories and distribution |date=1997 |publisher=Wiley |isbn=0471047015 |location=New York |url-access=registration}}

A biennial plant, hemlock produces leaves at its base the first year but no flowers. In its second year it produces white flowers in umbrella-shaped clusters.{{cite web |title=Poison Hemlock |url=http://store.msuextension.org/publications/AgandNaturalResources/MT200013AG.pdf |access-date=3 May 2015 |website=store.msuextension.org |publisher=Montana State University}}

{{gallery|mode=packed

|Conium maculatum - Köhler–s Medizinal-Pflanzen-191.jpg|19th-century illustration

|Gefleckterschierling.jpg|Vertically growing specimen

|CMchinoCa.jpg|Specimen in Chino, California

|Poison Hemlock.jpg|Flowers

|Hemlockseeds.jpg|Seed heads in late summer

}}

Hemlock can be confused with the wild carrot plant (Daucus carota, sometimes called Queen Anne's lace). Wild carrot has a hairy stem without purple markings, and grows less than {{Convert|1|m|ft|abbr=on|frac=2}} tall.{{cite web | author = DNRP-WLRD-RRS Staff | date = November 28, 2016 | title = Poison-hemlock | url = http://www.kingcounty.gov/environment/animalsAndPlants/noxious-weeds/weed-identification/poison-hemlock.aspx | access-date=January 23, 2017 | work = Noxious Weeds in King County, Weed Identification Photos | location = Seattle, WA | publisher = Department of Natural Resources and Parks (DNRP), Water and Land Resources Division (WLRD), Rural and Regional Services (RRS) section }} One can distinguish the two from each other by hemlock's smooth texture, vivid mid-green colour, purple spotting of stems and petioles and typical height of the flowering stems being at least {{Convert|1.5|m|ft|abbr=on|frac=2}}, twice the maximum for wild carrot. Wild carrots have hairy stems that lack the purple blotches.{{Cite book |last=Nyerges |first=Christopher |title=Foraging Washington: Finding, Identifying, and Preparing Edible Wild Foods |publisher=Falcon Guides |year=2017 |isbn=978-1-4930-2534-3 |location=Guilford, CT |oclc=965922681}}{{Cite web |url=http://ravensroots.org/blog/2015/6/26/poison-hemlock-id |title=How to Tell the Difference Between Poison Hemlock and Queen Anne's Lace |date=2 July 2015 |access-date=2021-05-03 |archive-date=2021-05-19 |archive-url=https://web.archive.org/web/20210519074353/http://ravensroots.org/blog/2015/6/26/poison-hemlock-id |url-status=live }}

The species can also be confused with harmless cow parsley (Anthriscus sylvestris, also sometimes called Queen Anne's lace).{{Cite web |title=Poison Hemlock (Conium maculatum) |url=https://www.ars.usda.gov/pacific-west-area/logan-ut/poisonous-plant-research/docs/poison-hemlock-conium-maculatum/ |website=USDA Agricultural Research Service}}

The plant should not be visually confused with the North American-native Tsuga, a coniferous tree sometimes called the hemlock, hemlock fir, or hemlock spruce, from a slight similarity in the leaf smell. The ambiguous shorthand of 'hemlock' for this tree is more common in the US dialect than the plant it is actually named after.{{Citation needed|date=June 2021}} Similarly, the plant should not be confused with Cicuta (commonly known as water hemlock).

The genus name "Conium" refers to koneios, the Greek word for 'spin' or 'whirl', alluding to the dizzying effects of the plant's poison after ingestion. In the vernacular, "hemlock" most commonly refers to the species C. maculatum. Conium comes from the Ancient Greek κώνειον – kṓneion: "hemlock". This may be related to konas (meaning to whirl), in reference to vertigo, one of the symptoms of ingesting the plant.{{cite web |title=Conium maculatum |url=http://jan.ucc.nau.edu/plants-c/bio414/species%20pages/conium%20maculatum.htm |access-date=2012-07-06 |publisher=Northwestern Arizona University |archive-date=2012-06-23 |archive-url=https://web.archive.org/web/20120623113546/http://jan.ucc.nau.edu/plants-c/bio414/species%20pages/conium%20maculatum.htm |url-status=dead }}

C. maculatum, also known as poison hemlock, was the first species within the genus to be described. It was identified by Carl Linnaeus in his 1753 publication, Species Plantarum. Maculatum means 'spotted', in reference to the purple blotches characteristic of the stalks of the species.{{Cite web |title=Conium maculatum (poison hemlock) |url=https://www.cabi.org/isc/datasheet/14820 |access-date=2020-12-03 |website=www.cabi.org}}

In British and Australian English the most prominent vernacular name is hemlock. In American English it is typically called poison hemlock, though this name is also used elsewhere. Less frequent names used in both America and Australia include spotted hemlock and poison parsley.{{cite book |last1=Coffey |first1=Timothy |date=1993 |title=The History and Folklore of North American Wildflowers |url=https://archive.org/details/historyfolklore00timo/page/157 |url-access=registration |language=en |location=New York |publisher=Facts on File |page=157 |isbn=978-0-8160-2624-1 |access-date=24 November 2024}} Other local or infrequent names in the US include bunk, California-ferm, cashes, herb-bonnet, kill-cow, Nebraska-fern, poisonroot, poison-snakeweed, St. Bennet's-herb, snakeweed, stinkweed, and wode-whistle. In Australia it is occasionally called wild carrot or wild parsnip. In Hiberno-English it may be called devil's bread or devil's porridge.

The hemlock plant is native to Europe and the Mediterranean region.{{cite journal|last1=Vetter|first1=J|title=Poison Hemlock (Conium maculatum L.)|journal=Food Chem Toxicol|date=September 2004|volume=42|pages=1374–82|pmid=15234067|doi=10.1016/j.fct.2004.04.009|issue=9}}

It exists in some woodland (and elsewhere) in most British Isles counties;{{cite book|last1=Clapham|first1=A.R.|last2=Tutin|first2=T.G.|last3=Warburg|first3=E.F.|date=1968|title=Excursion Flora of the British Isles|publisher=Cambridge University Press |edition=2nd|isbn=0521-04656-4}} in Ulster these are particularly County Down, County Antrim and County Londonderry.{{cite book|editor-last=Hackney|editor-first=P.|date=1992|title=Stewart & Corry's Flora of the North-east of Ireland|publisher=Institute of Irish Studies and The Queen's University of Belfast|isbn=0-85389-446-9}}

It has become naturalised in Asia, North America, Australia and New Zealand.{{cite web|author=Zehui, Pan|author2=Watson, Mark F.|name-list-style=amp|title=31. Conium Linnaeus, Sp. Pl. 1: 243. 1753|work=Flora of China|url= http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=107860|access-date=January 23, 2017}} See also the substituent page: {{cite web|url= http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200015502|access-date=January 23, 2017|title=1. Conium maculatum Linnaeus, Sp. Pl. 1: 243. 1753|work=Flora of China}}{{Cite web |url=http://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:apni.taxon:451627 |title=Atlas of Living Australia, Conium maculatum L., Carrot Fern |access-date=2015-06-13 |archive-url=https://web.archive.org/web/20150919165822/http://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:apni.taxon:451627 |archive-date=2015-09-19 |url-status=dead }} It is sometimes encountered around rivers in southeast Australia and Tasmania.{{cite web |title=Hemlock, Carrot Fern, Poison Hemlock, Poison Parsley, Spotted Hemlock, Wild Carrot, Wild Parsnip |url=https://weeds.org.au/profiles/hemlock-carrot-fern/ |website=Weeds Australia - profiles |publisher=Centre for Invasive Species Solutions (CISS) |access-date=30 January 2024 |language=en-AU |date=2021}} Infestations and human contact with the plant are sometimes newsworthy events in the U.S. due to its extreme toxicity.{{Cite web |url=https://beehabitat.com/poison-hemlock-can-kill-you-in-3-hours-or-less |title=Poison Hemlock |access-date=2022-11-29 |archive-date=2022-11-29 |archive-url=https://web.archive.org/web/20221129033902/https://beehabitat.com/poison-hemlock-can-kill-you-in-3-hours-or-less/ |url-status=live }}{{Cite web |url=https://www.dallasnews.com/news/2023/06/03/poison-hemlock-was-spotted-in-a-dallas-suburb-heres-what-you-should-know-about-the-plant/ |first=Noor |last=Adatia |title=Poison hemlock was spotted in a Dallas suburb. Here's what you should know about the plant. |work=The Dallas Morning News |date=2023-06-03 |access-date=2023-06-03 |archive-date=2023-06-03 |archive-url=https://web.archive.org/web/20230603204722/https://www.dallasnews.com/news/2023/06/03/poison-hemlock-was-spotted-in-a-dallas-suburb-heres-what-you-should-know-about-the-plant/ |url-status=live }}

The plant is often found in poorly drained soil, particularly near streams, ditches, and other watery surfaces. It also appears on roadsides, edges of cultivated fields, and waste areas. Conium maculatum grows in quite damp soil,{{Cite web |url=https://plantatlas2020.org/atlas/2cd4p9h.brm |title=Online Atlas of the British and Irish Flora: Conium maculatum |access-date=2014-08-07 |archive-date=2014-07-14 |archive-url=https://web.archive.org/web/20140714114749/http://www.brc.ac.uk/plantatlas/index.php?q=plant%2Fconium-maculatum |url-status=live }} but also on drier rough grassland, roadsides and disturbed ground. It is used as a food plant by the larvae of some lepidoptera, including silver-ground carpet moths and particularly the poison hemlock moth (Agonopterix alstroemeriana). The latter has been widely used as a biological control agent for the plant.{{Cite journal|last1=Castells|first1=Eva|last2=Berenbaum|first2=May R. |date=June 2006|title=Laboratory Rearing of Agonopterix alstroemeriana, the Defoliating Poison Hemlock (Conium maculatum L.) Moth, and Effects of Piperidine Alkaloids on Preference and Performance |url=http://ddd.uab.cat/record/125702|journal=Environmental Entomology|volume=35|issue=3|pages=607–615|doi=10.1603/0046-225x-35.3.607|s2cid=45478867|doi-access=free}} Hemlock grows in the spring, when much undergrowth is not in flower and may not be in leaf. All parts of the plant are poisonous.{{cite web |title=Poison Hemlock (Conium maculatum) |url=https://www.ars.usda.gov/pacific-west-area/logan-ut/poisonous-plant-research/docs/poison-hemlock-conium-maculatum/ |website=Agricultural Research Service |publisher=U.S. Department of Agriculture |access-date=30 January 2024 |date=26 June 2018}}

Hemlock contains coniine and some similar poisonous alkaloids, and is poisonous to all mammals (and many other organisms) that eat it. Intoxication has been reported in cattle, pigs, sheep, goats, donkeys, rabbits, and horses. Ingesting more than 150–300 milligrams of coniine, approximately equivalent to six to eight hemlock leaves, can be fatal for adult humans.{{Cite journal| doi = 10.3390/molecules22111962| issn = 1420-3049| volume = 22| issue = 11| last1 = Hotti| first1 = Hannu| last2 = Rischer| first2 = Heiko| title = The killer of Socrates: Coniine and Related Alkaloids in the Plant Kingdom| journal = Molecules| date = 2017-11-14| page = 1962| pmid = 29135964| pmc = 6150177| doi-access = free}} The seeds and roots are more toxic than the leaves.{{Cite book|date=1997-07-01|title=IPCS INCHEM: International Programme on Chemical Safety}} Farmers also need to ensure that the hay fed to their animals does not contain hemlock. Hemlock is most poisonous in the spring when the concentration of γ-coniceine (the precursor to other toxins) is at its peak.{{cite book|last1=Cheeke|first1=Peter|title=Toxicants of Plant Origin: Alkaloids, Volume 1|date=31 Aug 1989|publisher=CRC Press|location=Boca Raton, Florida|isbn=978-0849369902|page=118|edition=1}}{{cite web|title=Poison Hemlock: Options for Control|url=http://www.co.lincoln.wa.us/WeedBoard/controloptions/poisonhemlock.pdf|website=co.lincoln.wa.us|publisher=Lincoln County Noxious Weed Control Board|access-date=3 May 2015|archive-url=https://web.archive.org/web/20160304080259/http://www.co.lincoln.wa.us/WeedBoard/controloptions/poisonhemlock.pdf|archive-date=4 March 2016|url-status=dead}}

File:(S)-Coniine Structural Formula V.1.svgs, the (S)-(+) isomer, of coniine, where natural mixtures are considered likely racemates (equal mixtures) of this and the (R)-(–) isomer.{{cite journal |author1=Stephen T. Lee |author2=Benedict T. Green |author3=Kevin D. Welch |author4=James A. Pfister |author5=Kip E. Panter |year=2008 |title=Stereoselective potencies and relative toxicities of coniine enantiomers |journal=Chemical Research in Toxicology |volume=21 |issue=10 |pages=2061–2064 |doi=10.1021/tx800229w|pmid=18763813 }}]]

C. maculatum is known for being extremely poisonous. Its tissues contain a number of different alkaloids. In flower buds, the major alkaloid found is γ-coniceine. This molecule is transformed into coniine later during the fruit development.{{Cite journal|last=Cromwell|first=B. T.|date=October 1956|title=The separation, micro-estimation and distribution of the alkaloids of hemlock (Conium maculatum L.)|journal=Biochemical Journal|volume=64|issue=2|pages=259–266|doi=10.1042/bj0640259|pmid=13363836|pmc=1199726|issn=0264-6021}} The alkaloids are volatile; as such, researchers assume that these alkaloids play an important role in attracting pollinators such as butterflies and bees.{{Citation|last=Roberts|first=Margaret F.|chapter=Enzymology of Alkaloid Biosynthesis|date=1998|pages=109–146|publisher=Springer US|isbn=9781441932631|doi=10.1007/978-1-4757-2905-4_5|title=Alkaloids}}

Conium contains the piperidine alkaloids coniine, N-methylconiine, conhydrine, {{chem name|pseudoconhydrine}} and gamma-coniceine (or g-coniceïne), which is the precursor of the other hemlock alkaloids.{{cite journal |last1=Schep |first1=L. J.| last2=Slaughter |first2=R. J.| last3=Beasley |first3=D. M. |title= Nicotinic Plant Poisoning |journal=Clinical Toxicology |volume=47 |issue=8 |pages=771–781 |year=2009 |pmid=19778187 |doi=10.1080/15563650903252186|s2cid=28312730}}{{cite journal |last=Reynolds |first=T. |title=Hemlock Alkaloids from Socrates to Poison Aloes |journal=Phytochemistry |volume=66 |issue=12 |pages=1399–1406 |date=June 2005 |pmid=15955542 |doi=10.1016/j.phytochem.2005.04.039|bibcode=2005PChem..66.1399R }}{{cite journal |last=Vetter |first=J. |title=Poison Hemlock (Conium maculatum L.) |journal=Food and Chemical Toxicology |volume=42 |issue=9 |pages=1373–1382 |date=September 2004 |pmid=15234067 |doi=10.1016/j.fct.2004.04.009}}{{Cite web|url=http://www.toxinz.com/Demo/6/UExIMDIyLzEwNGg=|title=Conium maculatum TOXINZ - Poisons Information|website=www.toxinz.com|access-date=2017-05-29|archive-date=2017-05-23|archive-url=https://web.archive.org/web/20170523120448/http://www.toxinz.com/Demo/6/UExIMDIyLzEwNGg=|url-status=dead}}

Coniine has pharmacological properties and a chemical structure similar to nicotine.{{cite web |last=Brooks |first=D. E. |title=Plant Poisoning, Hemlock |date=2010-06-28 |url=http://emedicine.medscape.com/article/821362-overview |publisher=eMedicine |work=MedScape |access-date=2012-03-02}} Coniine acts directly on the central nervous system through inhibitory action on nicotinic acetylcholine receptors. Coniine can be dangerous to humans and livestock. With its high potency, the ingestion of seemingly small doses can easily result in respiratory collapse and death.{{cite book |title=Edible and Medicinal Plants of the West |last=Tilford |first=Gregory L. |isbn=978-0-87842-359-0|year=1997 |publisher=Mountain Press }}

The alkaloid content in C. maculatum also affects the thermoregulatory centre by a phenomenon called peripheral vasoconstriction, resulting in hypothermia in calves.{{Cite journal|last1=López|first1=T.A.|last2=Cid|first2=M.S.|last3=Bianchini|first3=M.L.|date=June 1999|title=Biochemistry of hemlock (Conium maculatum L.) alkaloids and their acute and chronic toxicity in livestock. A review|journal=Toxicon|volume=37|issue=6|pages=841–865|doi=10.1016/s0041-0101(98)00204-9|pmid=10340826|bibcode=1999Txcn...37..841L |issn=0041-0101}} In addition, the alkaloid content was also found to stimulate the sympathetic ganglia and reduce the influence of the parasympathetic ganglia in rats and rabbits, causing an increased heart rate.{{Cite journal|last1=Forsyth|first1=Carol S.|last2=Frank|first2=Anthony A.|date=July 1993|title=Evaluation of developmental toxicity of coniine to rats and rabbits|journal=Teratology|volume=48|issue=1|pages=59–64|doi=10.1002/tera.1420480110|pmid=8351649|issn=0040-3709}}

Coniine also has significant toxic effects on the kidneys. The presence of rhabdomyolysis and acute tubular necrosis has been shown in patients who died from hemlock poisoning. A fraction of these patients were also found to have acute kidney injury.{{cite journal|title=Clinical spectrum of accidental hemlock poisoning: neurotoxic manifestations, rhabdomyolysis and acute tubular necrosis|pmid=1798593|volume=6|issue=12|year=1991|journal=Nephrol. Dial. Transplant.|pages=939–43|last1=Rizzi|first1=D|last2=Basile|first2=C|last3=Di Maggio|first3=A|display-authors=et al|doi=10.1093/ndt/6.12.939}} Coniine is toxic for the kidneys because it leads to the constriction of the urinary bladder sphincter and eventually the accumulation of urine.{{Citation|chapter=Poison Hemlock (Conium maculatum L.)|title=Medical Toxicology of Natural Substances: Foods, Fungi, Medicinal Herbs, Plants, and Venomous Animals|pages=796–799|publisher=John Wiley & Sons, Inc.|isbn=9780470330319|doi=10.1002/9780470330319.ch131|first=Donald G.|last=Barceloux|year=2008}}

A short time after ingestion, the alkaloids induce potentially fatal neuromuscular dysfunction due to failure of the respiratory muscles. Acute toxicity, if not lethal, may resolve in spontaneous recovery, provided further exposure is avoided. Death can be prevented by artificial ventilation until the effects have worn off 48–72 hours later. For an adult, the ingestion of more than 100 mg (0.1 gram) of coniine (about six to eight fresh leaves, or a smaller dose of the seeds or root) may be fatal. Narcotic-like effects can be observed as soon as 30 minutes after ingestion of green leaf matter of the plant, with victims falling asleep and unconsciousness gradually deepening until death a few hours later.{{cite journal |title=Three deaths from hemlock poisoning |url-access=subscription |doi=10.5694/j.1326-5377.1995.tb138553.x |url=https://pubmed.ncbi.nlm.nih.gov/7791646/ |last1=Drummer |first1=Olaf H. |first2=Anthony N. |first3=Paul J. |first4=Kerryn L. |first5=Michael H.|last2=Roberts |last3=Bedford |last4=Crump |last5=Phelan |pmid= 7791646 |volume=162 |issue=5 |year=1995 |pages=592–593 |journal=The Medical Journal of Australia|s2cid=45736238 }}

The onset of symptoms is similar to that caused by curare, with an ascending muscular paralysis leading to paralysis of the respiratory muscles, causing death from oxygen deprivation.{{cite web |url=http://www.inchem.org/documents/pims/plant/conium.htm |title=Conium maculatum L. |work=Inchem |publisher=IPCS (International Programme on Chemical Safety) |access-date=2012-07-06}}

It has been observed that poisoned animals return to feed on the plant after initial poisoning. Chronic toxicity affects only pregnant animals when they are poisoned at low levels by C. maculatum during the fetus's organ-formation period; in such cases the offspring is born with malformations, mainly palatoschisis and multiple congenital contractures (arthrogryposis). The damage to the fetus due to chronic toxicity is irreversible. Though arthrogryposis may be surgically corrected in some cases, most of the malformed animals die.

Such losses may be underestimated, at least in some regions, because of the difficulty in associating malformations with the much earlier maternal poisoning.

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. It is a common myth that C. maculatum alkaloids can enter the human food chain via milk and fowl, and scientific studies have disproven these claims.{{cite journal |last1=Frank |first1=A. A. |last2=Reed |first2=W.M. |date=April 1990 |title=Comparative Toxicity of Coniine, an Alkaloid of Conium maculatum (Poison Hemlock), in Chickens, Quails, and Turkeys |journal=Avian Diseases |volume=34 |issue=2 |pages=433–437 |doi=10.2307/1591432 |jstor=1591432 |pmid=2369382 }}

{{anchor|Socrates}}

File:David - The Death of Socrates.jpg, by Jacques-Louis David (1787)]]

In ancient Greece, hemlock was used to poison condemned prisoners. Conium maculatum is the plant that killed Theramenes, Socrates, Polemarchus, and Phocion.{{cite book|last1=Blamey|first1=M.|last2=Fitter|first2=R.|last3=Fitter|first3=A.|year=2003|title=Wild flowers of Britain and Ireland: The Complete Guide to the British and Irish Flora|publisher=A & C Black|location=London|isbn=978-1408179505}} Socrates, the most famous victim of hemlock poisoning, was accused of impiety and corrupting the minds of the young men of Athens in 399 BC, and was sentenced to death at his trial. He decided to take a potent infusion of hemlock.

• List of poisonous plants

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{{NIE Poster|year=1905|Hemlock}}

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• {{cite web |url=http://rbg-web2.rbge.org.uk/cgi-bin/nph-readbtree.pl/feout?FAMILY_XREF=&GENUS_XREF=Conium&SPECIES_XREF=&TAXON_NAME_XREF=&RANK= |publisher=Royal Botanic Garden Edinburgh |work=Flora Europaea |title=Conium}}

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Category:Apioideae

Category:Flora of Europe

Category:Plants described in 1753

Category:Taxa named by Carl Linnaeus