Practical ecological knowledge for the temperate reader.

Poison Hemlock - Conium maculatum

Family: Carrot[E-flora]

Habitat / Range Wet to mesic ditches and disturbed sites in the lowland zone; locally common in in SW BC (known in the Victoria area and Vancouver) rare in SC BC; introduced from Europe.[IFBC-E-flora]

Origin Status: Exotic. [E-flora]


Conium maculatum is a BIENNIAL growing to 2 m (6ft) by 1 m (3ft 3in).
It is hardy to zone (UK) 5 and is not frost tender. It is in flower from Jun to July. The flowers are hermaphrodite (have both male and female organs) and are pollinated by Insects.The plant is self-fertile.
Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: acid, neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.[PFAF]

General: Robust biennial herb from a stout whitish taproot, with a disagreeable odour, especially when crushed; stems erect, freely branched, purple-blotched, hollow, 0.5-3 m tall, glabrous, glaucous. [IFBC-E-flora]
Leaves: Stem leaves pinnately dissected, fernlike, with small ultimate segments giving the plant a lacy appearance; leaf stalks enlarged and sheathing at the base, the blades 15-30 cm long.[IFBC-E-flora]
Flowers: Inflorescence terminal and axillary in many compound umbels; flowers white; involucral bracts small, lance-shaped.[IFBC-E-flora]
Fruits: Egg-shaped, somewhat flattened, 2-2.5 mm long, glabrous, with prominent, raised, often wavy ribs.[IFBC-E-flora]


Birth Defects: One of several species associated with limb deformations (multiple congeni- tal contractures), known as ‘‘crooked calf disease’’ and cleft palate in in cattle, goats and pigs.[Molyneux et al.]

Deadly: Plants highly poisonous. [IFBC-E-flora]

Edible Uses It has been used as a food plant in the early spring. We recommend avoiding it and also any plant that in any way resembles it, unless you are absolutely familiar with everything involved. [Harrington]

Curiously the toxicity of the leaves varies with climate and the age of the plant. People have reportedly eaten young leaves with no ill effects, a practice I would strongly discourage. [Nyerges]

Medicinal Uses
Hemlock is a very poisonous plant that has a long history of medicinal use, though it is very rarely used in modern herbalism[238, 254]. It is a narcotic plant that sedates and relieves pain[238]. The plant contains coniine, an extremely toxic substance that can also cause congenital defects[254]. Because of the extremely toxic nature of this herb, it is seldom employed nowadays[232]. Use with extreme caution and only under the guidance of a qualified practitioner[21, 238]. See also the notes above on toxicity. [PFAF]

Lore Poison hemlock is forever associated with Socrates, one of the great philosophers of ancient Athens. The Socratic method involves asking a series of questions to make you think, leading to the truth, which Socrates claimed lay within. When his students began questioning authority, he was tried and convicted of "corrupting the youth." At age seventy, he drank a cup of poison-hemlock tea and, according to Plato, died painlessly.[Wildman]

Plato wrote an account of Socrates' death and physical reactions (from Phaedo) as follows:

Crito made a sign to one of the attendants, who soon returned with a man bringing the poison in a drinking cup. Socrates said, ""Tell me, my friend, what should I do?" "Only drink it, and then walk around until your legs begin to feel heavy," he replied, handing the cup, "then lie down."

Socrates walked about until his legs began to feel heavy. Then he said his legs felt heavy and he lay down on his back as he had been instructed. The man who administered the poison kept his hand on Socrates and after a short time examined his legs and feet. Then he pressed his foot hard, and asked if he could feel anything. Socrates said he couldn't. After that, the man did the same to Socrates' legs, and moving his hand up the body, he showed us that Socrates was becoming cold and numb. Later the attendant felt Socrates again and said that when the numbness reached the heart, Socrates would die. It was already almost to his waist when Socrates uncovered his face and spoke his last words.

"Crito, I owe a cock to the god who heals, Asclepius. See that my debt is paid." "It shall be done," said Crito with complete understanding. "Is there anything else?"

But Socrates made no reply to his question. After a little while Socrates moved slightly, and the man uncovered him. His eyes had become fixed. When Crito saw this, he closed Socrates' eyes and mouth. "So ended the life of our dear friend," said Phaedo. [Nyerges]


Abstract - Previous work, based on analyses of samples of developing fruits collected at weekly intervals, has been confirmed. Samples were also collected at 4-hourly and 2-hourly intervals and analyses showed that remarkably rapid changes in the alkaloidal picture took place at short intervals during 24 hr. Further- more, as the coniine content increased, the y-coniceine content decreased and vice versa. This interrelationship was particularly marked during the critical stages of pericarp development, but was not obvious during the development of the vegetative parts, where y-coniceine and conhydrine were the only known alkaloids detected. Since coniine and y-coniceine differ only by two hydrogen atoms, it is suggested that these two alkaloids are involved in oxidation-reduction processes in the developing pericarp. The occurrence of the minor alkaloids conhydrine and N-methyl coniine and the presence of some unknown alkaloids are also reported and commented on. [Phytochemistry, 1961]

Unknown Alkaloids

The results of all the work on hemlock alkaloids up to this point would be consistent with a slow accumulation of alkaloids as minor end products of metabolism together with gradual changes in their composition. Our work on 4-hourly and 2-hourly samples has however shown that remarkably rapid changes in the composition and amounts of alkaloid occurred over short periods of time. [Phytochemistry, 1961]

It is well known that much of the coniine is stored in the inner layers of the pericarp, in the endocarp or “coniine layer”. [Phytochemistry, 1961]

Relation to the Development of the Pericarp
During the first few weeks of fruit development there is a rapid increase in the average alkaloidal content. During this period the pericarp, to which the alkaloids are restricted, develops rapidly and marked anatomical changes take place.’ The increasing “demands” of the developing pericarp for alkaloids may therefore be closely related to the increasing number of living cells. This would be consistent with the view already expressed, that the alkaloids play a significant part in the intracellular metabolism of the pericarp. [Phytochemistry, 1961]

(Herbal)Essential oil, % dry wt: 0.07 [1]
(Leaf)Essential oil, % dry wt: 0.08 [2]
Seed and Pericarp
Mass of 1,000, g: 7.9 [3]
Oil, % dry wt: 13.2 [3], 11.3–17.5 [2]
Essential oil, % dry wt: 0.017–0.07 [1, 2][LEOVP]


Leaves - Essential Oil - 90% inhibition at 1,000 μg/ml. Vs. A. parasiticus. [Antifungal]

The plant is poisonous. The effects of the drug are caused by coniine in particular. Toxic doses given to mice, rats, guinea pigs and cats provoked the autonomous ganglion, clonic and tonal contractions of individual limbs, cramps and eventually, paralysis. Small doses given to mice led to blood pressure reduction in the short term. Higher doses resulted in a rise in blood pressure. Smaller doses stimulated respiration in cats, while higher doses impeded or slowed down the initial stimulus. In isolated guinea pig ileum, coniine brought on contractions. In isolated perfused rabbit hearts, coniine was negatively inotropic while a stable heart beat was maintained. With anesthetized cats, a suppression of the muscle contraction reflex took place. Feeding or injecting lethal doses of coniine into cows, horses, pigs, sheep and hamsters was initially stimulating, producing twitching of the eyes and ears, which was followed by muscular debility, collapse, limpness and deam through paralysis. Coniine absorbed through the skin and mucous membranes is stimulating at first, then causes gradual paralysis of the spinal cord and blockage of the medulla oblongata. Nicotine-like receptors are at first activated, then paralyzed. [PDR]

Medicinal Usage
For a time, both methylconine and conine, the deadly alkaloids present in this plant, were used by United States physicians. Conine (CSH17N), a volatile, colorless, oily substance was extracted from the seeds and used in very small amounts as an antispasmodic, sedative, and pain reliever. It is rarely if ever, used as such today. [Nyerges]

Very poisonous! Contains up to four alkaloids, all of which (to varying degrees) paralyze the central nervous system, especially the nerves controlling the respiratory organs. It effects paralysis of the peripheral endings of the motor nerves with only a slight effect on the nerves of sensation. Thus, Socrates was clear thinking after he drank the tea, yet his body and muscle use-especially his ability to breathe-quickly diminished. [Nyerges]
In Morocco, this species was one of several ingredients used in a polyherbal recipe that was burned to produce smoke that was considered useful for inducing abortions in pregnant women (Merzouki et al. 2000). See Atractylis gummifera L. for a list of the other species used. [UAPDS]

POISON HEMLOCK (Conium maculatum L.) X [HMH Duke]
Activities (Poison Hemlock) — Alterative (f; CRC); Analgesic (f; CRC); Anaphrodisiac (f; CRC); Antinicotinic (1; PH2); Antispasmodic (f; CRC); Aphrodisiac (f; CRC); Hypertensive (1; PH2); Hypotensive (1; PH2); Negative Inotropic (1; PH2); Nervine (f; CRC); Nicotinic (1; PH2); Paralytic (1; PH2); Poison (2; DEM; PH2); Respiradepressant (1; PH2); Respirastimulant (1; PH2); Sedative (f; CRC); Teratogenic (1; PHR; PH2).
Dosages (Poison Hemlock) — Do not use it (JAD). Many of the indications are homeopathic.

Maximum dose 300 mg; standard dose 100 mg; not to exceed 1500 mg/day (HHB; PHR; PH2).

Contraindications, Interactions, and Side Effects (Poison Hemlock) — Not covered (AHP).

Classed by the FDA as unsafe containing the poisonous alkaloid coniine and other closely related alkaloids. Can cause contact dermatosis. Ingestion may cause debility, drowsiness, nausea, labored respiration, paralysis, asphyxia, and death. “Following lethal doses, animals rapidly begin to show symptoms; among them: paralysis of the tongue, mydriasis, head pressure, giddiness, nausea, vomiting, diarrhea, and collapse into central paralysis, first the feet and legs, then the buttocks, arms, then paralysis of swallowing and speech. With increasing dyspnea and cyanosis, death ensues through central respiratory paralysis. LD is about 500–1000 mg coniine for man.” (CRC; HHB) (Note that in CRC (1985) I misquoted HHB and said 500 to 100).


Herbivorous animals do not seem to be poisoned by eating it (it is said that a Cambridgeshire way of controlling unruly horses was to pound hemlock in a mortar until it was finely powdered, and then to rub it on their noses (Porter. 1969)), but it seems that carnivores are more susceptible (Sanford). It is also said to be most poisonous in the southern part of its range (Salisbury. 1964). Martin. 1703 described the effects of eating hemlock: “Fergus Caird, an empiric, living in the village Taliste (Talisker?), having by mistake eaten hemlock-root, instead of the white wild-carrot, his eyes did presently roll about, his countenance became very pale, his sight had almost failed him, the frame of his body was all in a strange convulsion, and his pudenda retired so inwardly, that there was no discerning whether he had been male or female. All the remedy given him in this state was a draught of hot milk, and a little aqua-vitae added to it, which he no sooner drank, but he vomited presently after, yet the root still remained in his stomach.
They continued to administer the same remedy for the space of four or five hours together, but in vain; and in about an hour after they ceased to give him anything, he voided the root by stool, and then was restored to his former state of health…”. [DPL Watts]

A plant as poisonous as this would naturally have an association with witches. “Root of hemlock digged in dark” was one of the ingredients in the witches’ cauldron in Macbeth, and Summers claimed that it was used by them either as a poison or as a drug, favoured mainly because of its soporific effects. The soporific effect is uppermost in a story told by Coles that “if asses do chaunce to feed upon Hemlock they will fall so fast asleepe that they will seeme to be dead. In so much that some thinking them to be dead have flayed off their skins, yet after the Hemlock had done operating they have stirred and wakened out of their sleep, to the griefe and amazement of the owners, and to the laughter of others”. On the fringes of the association with witchcraft is an Irish love charm that consisted of taking ten leaves of hemlock, dried and powdered, and mixing this powder in food or drink (Wilde. 1902). Some say that it is the purple blotches on its stem that gives it a bad name, for these streaks are copies of the brand put on Cain’s brow when he had committed murder (Skinner).[DPL Watts]

The fruits are the only convenient source of the alkaloid coniine (or Conia), which was introduced into British medicine in 1864. The pure drug has been used sometimes in soothing cancer pain (Schauenberg & Paris). The plant itself was used in Anglo-Saxon times, and is mentioned as early as the 10th century, in the vocabulary of Aelfric, Archbishop of Canterbury, as Cicuta, hemlic (Fluckiger & Hanbury). It was, in fact, an ingredient in the narcotic drink called dwale (Voigts & Hudson). It has been used in the past in dealing with a cataract. Buchan, in the 18th century congratulated himself on curing a cataract “by giving the patient purges with calomel, keeping a poultice of fresh hemlock constantly upon the eye, and a perpetual blister on the neck”.[DPL Watts]

In parts of Ireland, it was used for giddiness (Barbour), and an Irish recipe of about 1450 recommended it for the falling sickness, epilepsy (Wilde. 1890). Boiled hemlock was widely used in Ulster (and in the Isle of Man (Moore, Morrison & Goodwin)) to reduce swellings in men and animals. It could not be used if there was a cut or scratch near the swelling (Foster). On the other hand, the leaves, dried and powdered, were used in Essex to be put on cuts (V G Hatfield. 1994), and in Ireland a pain-killing poultice used to be made by mixing hemlock leaves with linseed meal (Moloney), a preparation also used on boils (Maloney).[MPFT]

The true hemlock is known as a macrofossil from Roman sites in Wales, and that fact taken together with its well-known use in Classical medicine and presence in the Anglo-Saxon herbals suggest that it has had many centuries to infiltrate any older, indigenous tradition of its use that may have existed here. Much of its distribution as a wild plant in the British Isles today may indeed be a legacy of its cultivation for medicinal purposes. [DPL Watts]

In Ireland, on the other hand, though hemlock poultices have been similarly in widespread use, especially in the north of the country,98 for treating swellings and bad sores of all kinds, no records have been traced of their being applied to cancers. They have, however, been valued there additionally for rheumatism (Wicklow99), burns (Kilkenny,100 Limerick101) and—unless ‘hemlock’ in this case refers to hogweed—wounds.102 Quite unrelated to any of the foregoing, though, has been the reputation the plant has enjoyed in certain (unspecified) parts of Ireland as a means of curing giddiness.103[MPFT]

Cancer: "...hemlock juice as a cure for cancer in the mid-eighteenth century by the much-respected Viennese physician Anton Storck, which despite much scepticism in higher medical circles in Britain following ambiguous reports of its efficacy (suspected by William Withering to have resulted at least in part from using the wrong plant88) led to some percolating of the remedy downwards. Though the orthodox treatment took the form of swallowing pills made from a decoction of the leaves, a blacksmith in Cornwall is on record as having believed he had cured himself of a cancer by drinking immense quantities just of the juice over a period of three years.89 The normal practice in folk medicine, however, seems to have been the less daring one of poulticing external cancers with the leaves (as in Suffolk90 and Angus91), which was merely a version of the hemlock poultice in widespread use for sores and swelling more generally (as in Cambridgeshire,92 Berwickshire93 and the Isle of Man94). In the Isle of Man95 and the Highlands,96 though, cases of a drastic and much more painful alternative are known that involved extracting a tumour by its roots by means of a plaster-provided that was done at an early stage." [MPFT] In 1790, a Cornish blacksmith, Ralph Barnes, was supposed to have cured himself of a cancer by taking immense quantities of hemlock juice (Deane & Shaw) (primitive chemotherapy?). Equally unlikely is Buchan’s recommendation of it for the King’s Evil, but there is another usage that is perhaps not so unlikely: Granny Gray, of Littleport, in Cambridgeshire, used to make up pills from hemlock, pennyroyal and rue. They were famous in the Fen country for abortions (Porter. 1969) in the mid-19th century.[DPL Watts]

Abortive: It was no doubt the plant’s particular virulence that also caused it to be combined with pennyroyal (Mentha pulegium) and rue (the wholly cultivated Ruta graveolens Linnaeus) in a pill given at one time in the Cambridgeshire Fens for the purpose of inducing abortions.97[MPFT]

Propagation Seed - best sown in situ as soon as it is ripe in the late summer. It usually germinates in the autumn.[PFAF]

Growing Cycle Poison hemlock is a biennial, producing its ferny leaves the first year (in the spring) and flowering the second year (in the summer). [Nyerges]
A fairly common weed in Britain, it succeeds in most soils in sun or light shade and avoids acid soils in the wild. It prefers a damp rich soil[238].[PFAF]


Family: APIACEAE (Umbelliferae) - Carrot family

Biennial, taprooted; herbage glabrous, musty-scented. Stem: erect, branched. Leaf: blade ovate to triangular-ovate, pinnately dissected or compound, segments or leaflets lanceolate or oblong to ovate, serrate to 1–2-pinnately lobed. Inflorescence: umbels compound, terminal, lateral; bracts, bractlets small, few; rays, pedicels ± many, spreading-ascending. Flower: calyx lobes 0; petals wide, ± white, tips narrowed. Fruit: ovoid to spheric, ± compressed side-to-side; ribs ± equal, low; oil tubes 0; fruit axis divided to base. Seed: face grooved.
± 6 species: Europe, southern Africa. (Greek name used by Dioscorides) TOXIC: highly toxic alkaloids used in ancient Greece for capital punishment (e.g., Socrates); many human deaths, rarely eaten by livestock.


Local Species;

  1. Conium maculatum - Poison-hemlock [E-flora][PCBC][TSFTK]

Confusion with “hemlock” (Conium maculatum) There can be some confusion between the various water hemlock species and poison hemlock (Conium maculatum).16 “Water Hemlock” most commonly refers to Cicuta spp. such as Cicuta maculata, but can also refer to Conium maculatum (poison hemlock). Although many symptoms overlap, differentiation is important; in severe poisoning, Cicuta spp. causes seizures and potentially status epilepticus, whereas Conium maculatum results in respiratory paralysis, secondary to muscle weakness. The two plants can also be distinguished on the basis of their characteristic morphological properties: Conium maculatum has a single tap root, purple and spotted stem,4 while Cicuta spp. have branched root systems with tubules and an absence of purple spots.[TNS]


  1. [Antifungal] Antifungal Plants of Iran: An Insight into Ecology, Chemistry, and Molecular Biology, Mehdi Razzaghi-Abyaneh, Masoomeh Shams-Ghahfarokhi and Mahendra Rai, Antifungal Metabolites from Plants, 2013
  2. [E-flora], Accessed May 1, 2015
  3. [Jepson]2013. Conium, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on Jan 28 2015
  4. [LEOVP]A.I. Glushenkova (ed.), Lipids, Lipophilic Components and Essential Oils from Plant Sources, DOI 10.1007/978-0-85729-323-7, # Springer Science+Business Media, LLC 2012
  5. [Molyneux et al.]Phytochemicals: the good, the bad and the ugly?, Russell J Molyneux, Stephen T Lee, Dale R Gardner, Kip E Panter, Lynn F James, Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA 94710, USA. Phytochemistry (Impact Factor: 3.35). 11/2007; 68(22-24):2973-85. DOI: 10.1016/j.phytochem.2007.09.004 Source: PubMed
  6. [Montana] Montana Native Plants and Early peoples, Jeff Hart and Jacqueline Moore, Montana Historical Society Press, Helena, USA, 1976
  7. [PFAF], Accessed May 1, 2015
  8. [Phytochemistry, 1961] THE ALKALOIDS OF HEMLOCK (CONIUM MACULATUM L.).-II EVIDENCE FOR A RAPID TURNOVER OF THE MAJOR ALKALOIDS J. W. FAIRBAIRN and P. N. SUWAL School of Pharmacy, Brunswick Square, London, W.C.1 (Received 14 February 1961) Phytochcmistry. 1961. Vol. 1. pp. 38 to 46. Pqamon Press Ltd

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