If you live in the United States, you may have seen recent news reports and online warnings about an apparent resurgence and spread of the plant known as poison hemlock. Just earlier this month, it was reported by the Mansfield News Journal as spreading across the state of Ohio, causing concerns about its extreme toxicity and the danger to humans and livestock.

These reports may be giving you flashbacks to your social studies classes (hang on, didn’t some famous guy die from drinking hemlock, like way back in the old days?), but while your history teachers would undoubtedly be proud of your recall, it’s important to remember poison hemlock is still a very real threat to us today, especially if we run across it unawares. In fact, you may notice that it looks rather familiar…perhaps to a certain plant I’ve already posted about? (See my previous post on yarrow here.) You’re not imagining things; there are distinct similarities between the two in appearance, though their impacts on the human body are largely opposite.

Because hemlock has such a close resemblance to a common and well-loved medicinal herb, it’s imperative to understand and be able to spot the differences to stay safe. Let’s take a look at what poison hemlock is, its history and how to steer clear of this potentially deadly imposter.

What is Poison Hemlock?

Not to be confused with the hemlock tree, poison hemlock is a member of the carrot family (Apiaceae) and its Latin name is Conium maculatum. Its lacy, divided leaves spring from a smooth green stem, and it produces clusters of small white flowers in an umbel (umbrella-shaped) form. All parts of the plant are highly toxic to humans and animals; even a small touch can cause irritation to the skin. Hemlock has an unpleasant, rank and alkaline smell when the leaves are crushed. It contains alkaloid poisons that affect the central nervous system and can cause paralysis in the limbs, working inward to the respiratory muscles and leading to death.

Poison hemlock is native to North America, Europe and western Asia. It is now found in nearly every U.S. state after it was marketed in the 1800s as a fern for the garden. It prefers shaded areas with moist soil, but it can crop up near roadsides, the edges of fields, ditches, marshy areas and meadows.

Hemlock’s History

The Ancient World

The effects of hemlock were well-known in ancient Greece and Persia.  Physicians sometimes used hemlock to relieve conditions like arthritis and as a sedative, but such treatment was risky due to the extremely fine difference between a beneficial dose and a toxic one. (This should go without saying, but DO NOT TRY THIS AT HOME!) Most frequently, hemlock was used as a method of execution in this period.

Poison hemlock’s most well-remembered victim was the ancient philosopher, Socrates.  Despite his renown, Socrates was tried and convicted of polluting the minds of the youth of Athens, where he taught and served.  While the most famous account of his death, recorded by Plato, is questioned by scholars as to its factual accuracy, it is generally accepted that Socrates consumed a drink containing hemlock.  The hemlock’s toxicity would have gradually paralyzed all of his muscles, including his heart and lungs, causing death.

Hemlock’s infamy was not restricted to the ancient Mediterranean, however; it crops up in herbals through the centuries, even into the early 1900s. Let’s look at some examples to see how herbalists in successive time periods portrayed this plant.  

Medieval Europe

Our first stop is in the twelfth century, at a Benedictine monastery in modern-day Germany. You may be surprised to find that the widely-known and well-respected herbalist here was a woman! Hildegard von Bingen was the abbess, and alongside various musical and spiritual compositions, she also authored two medical texts, including Physica, one of the earliest-known herbals written by a woman.

Hildegard certainly doesn’t beat around the bush in her entry on hemlock. She immediately identifies the dangerous consequences of ingesting this plant:

“Hemlock (scherling) is hot and has danger in it so that, if a person eats it, it destroys everything that has been well and correctly established in his blood and humors.  It causes bad inundations in him, in the same way that storms make disturbances in the water.”

Yikes!  The message is clear: stay away! 

Yet despite its clear risks, Hildegard identified some instances in which hemlock can help when carefully administered:

“…one who has been badly stricken by spears and cudgels, or who has fallen from a high altitude so that his flesh and limbs are crushed, should cook hemlock in water and place the expressed water over the limbs which are injured.  He should tie a cloth over the area, and so dissipate the humors which have collected there.”

As with the ancient Greeks, medieval Europeans were aware of hemlock’s potential to heal, yet they greatly respected its power to harm.

Renaissance England

Skipping forward a few centuries to the Renaissance (or early modern) period, we find an era when knowledge of medical science was becoming increasingly available and accepted, yet a keen interest in plants and gardening spurred an increase in the number of herbals and plant guides being written.  One of the best-known volumes was The English Physician by Nicholas Culpeper. 

Reflecting trends of the time, Culpeper’s description of hemlock began with its striking appearance: 

“The common great hemlock groweth up with a green stalk, four or five feet high, and sometimes higher, full of red spots; at the joints are set very large winged leaves, which are divided into many other winged leaves, set one against another, dented on the edges, and of a sad green colour.  The stalks are branched towards the top, each bearing umbels of white flowers, which are followed by whitish flat seed. The root is long, white, hollow, and sometimes crooked, of a very strong, heady, and disagreeable smell.” 

Culpeper went on to advise that hemlock was very dangerous and must not be taken internally, though like Hildegard, he did acknowledge that if utilized in just the proper way, it could ease certain topical ailments. Interestingly, Culpeper wrote of a possible antidote to be used in the case of a patient who had mistakenly ingested hemlock, though even his own words sound remarkably unconvinced of its likelihood of success.  

The Age of Enlightenment

In the mid-18^th century, Austrian physician Anton von Stoerck studied the potential of several poisonous plants to be used in medical treatments.  His process of staged experimentation (first on animals, then on himself, then finally on patients) led the way toward the clinical trial model used today. 

Von Stoerck described the process and outcomes of his study of hemlock in An Essay on the Medical Nature of Hemlock, published in 1760, which he addressed and dedicated to the Holy Roman Empress, Maria Theresa. Inspired by accounts of successful treatments recorded by early writers like Pliny, von Stoerck experimented with hemlock extracts and powders. He detailed the outcome of 20 cases he treated, and though he concluded his essay with a series of additional questions he hoped to pursue, he remained convinced that with proper preparation, hemlock could be a medicinal asset to humankind. 

Modern/20th Century

By the early 20^th century, the medicinal use of hemlock had been well-established. Maud Grieve, author of 1931’s A Modern Herbal, credited such use back to the work of von Stoerck, though she qualified that “it has lost some of its reputation owing to the uncertain action of the preparations made from it.” Mrs. Grieve provided an overview of the practices of her day, which primarily relied on hemlock’s same sedative and antispasmodic properties that had been noted as far back as the ancients.  Yet despite the apparent acceptance of the plant’s benefits, Mrs. Grieve echoed the cautions of her forebears and emphasized that hemlock treatments must be dispensed with great care to avoid poisoning, paralysis and death. 

Today

Since the time of Mrs. Grieve’s writing, modern medicine has advanced and become sufficiently accessible in most regions where hemlock thrives that less reliance is placed on the curative properties of plants alone when treating physical ailments. As a result, safer and more effective remedies are available for the complaints previously treated with hemlock, eliminating the need to risk dangerous overdoses. Yet as recent news brings home, poison hemlock is still very much alive and well in our natural environment, and as such it continues to pose a toxic threat.

What’s Next?

Now that we’ve discussed the long and much-documented history of poison hemlock, we need to learn how to recognize it and – perhaps most importantly – avoid misidentifying it as another benign plant! Stay tuned for my next post on distinguishing dangerous hemlock from friendly yarrow, coming out on Friday, 7/2/21!

Sources and Further Reading

https://www.mansfieldnewsjournal.com/story/news/2021/06/19/dangerous-plant-blooming-rampantly-across-buckeye-state/7705613002/

https://www.growforagecookferment.com/poison-hemlock/

https://www.nps.gov/articles/poison-hemlock.htm

https://carnegiemnh.org/poisons-carnegie-hemlock/

https://www.newworldencyclopedia.org/entry/Hemlock

https://thatbiologist.wordpress.com/2015/01/08/a-short-history-of-poison-hemlock/

https://www.ucl.ac.uk/~ucgajpd/medicina%20antiqua/sa_hemlock.html

https://www.history.com/topics/ancient-history/socrates

https://www.botanical.com/botanical/mgmh/h/hemloc18.html#top

Von Bingen, Hildegard. Essay. In Hildegard Von Bingen’s Physica: the Complete English Translation of Her Classic Work on Health and Healing, translated by Priscilla Throop, 26–27. Rochester,, VT: Healing Arts Press, 1998. 

CULPEPER, NICHOLAS. Essay. In CULPEPER’S ENGLISH PHYSICIAN: and Complete Herbal (Classic Reprint), 200–201. London: FORGOTTEN Books, 2015. 

An essay on the medicinal nature of hemlock: … / translated from the Latin original. Written by Dr. Storck.