Species of the day: Hemlock

22 June 2020 | Posted in James Duncan , Plants
Species of the day: Hemlock
Hemlock © James Duncan

By James Duncan

Learning & Engagement Officer

Hemlock (Conium maculatum) likely needs little introduction for its reputation precedes it as a notoriously toxic member of the Apiaceae, the widely distributed 'carrot' or 'parsley' family. Known as the Umbellifers, they produce their flowers in 'umbrella-like' clusters and have leaves that are divided into distinct leaflets. Hemlock is a herbaceous biennial (taking two years to complete its reproductive life cycle) and may be surprisingly prolific, naturalising easily on damp ground such as roadside verges, byways, ditches, parkland edges and wasteland. Once it takes hold it may reach over two metres in height and is typically the tallest native umbellifer, though the monstrous and invasive Giant Hogweed (Heracleum mantegazzianum) grows significantly larger. 


Over the ages Hemlock has undoubtedly been mistaken with similar, harmless members of its own family, many of which are edible and have seen widespread medicinal use. In reality, it's not terribly difficult to identify for it has some distinctive traits. The biggest clue of all are the smooth, hairless, purple-blotched stems. The leaves are characteristically lacy, finely divided and resemble parsley, chervil and wild carrot. Hemlock foliage also happens to have a rather musty, foetid smell, somewhat indicative of its wholly poisonous nature. Many organisms, however, have evolved mechanisms to deal with its toxicity - it is visited by pollinators, plays host to a range of fungi and is utilised as a larval food-plant by a number of moth species. The genus name of Conium most likely derives from the Ancient Greek word koneion, suggesting a reference to 'whirl' or 'spin.' This may hint at the symptoms of vertigo experienced through ingestion.


Hemlock's most famous historical connection is of course its supposed responsibility for the death of Greek Philosopher, Socrates. He was put to death by the State of Athens in 399 BC, recorded by Plato in his renowned ancient dialogue, the Phaedo. Socrates was accused of impiety, both 'corruption of young minds' and 'neglect of the gods', the resulting punishment, enforced suicide by an infusion of Hemlock, used commonly for executions in Ancient Greece. All parts of the plant contain a number of toxic alkaloid compounds, poisonous not just to humans, but livestock and many higher vertebrates. Just one of these is coniine, a potent neurotoxin which acts on the central nervous system, leading to complete respiratory failure through muscular paralysis - with some mighty unpleasant side-effects prior. The combination of toxins mean that tiny doses may prove lethal and with no known antidote, artificial respiration remains the only treatment, essentially waiting until the effects wear off. It's really quite remarkable and rather humbling to consider the dark secrets harboured by some of our most common plants. 


Hemlock © James Duncan


  • david shaw:

    22 Jun 2020 18:24:00

    I think there is evidence that Plato’s account of Socrates death is accurate and that hemlock poisoning is not accompanied by convulsions and terrible pain. Problem is that the word hemlock is used for other poisonous plants including Hemlock water dropwort and many accounts of poisoning resulting in extreme pain refer to these plants. The Plato Society (“Hemlock poisoning and the Death of Socrates” ) has published an excellent article that explores the historical evidence including reports of 19th Century toxicologists who took hemlock poison to sudy its effects. They mention the painless lethargy described by Plato. Apart from that I really enjoyed the article. Where I live in northern italy it is very very common , in urban areas too though most people do not recognise the plant even though hey have heard of its role in the execution of Socrates.

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