Hemlock: The Philosopher's Poison

Poisonous Plants

Aug 1

A journey through the science, history, and mythology of one of the world's most infamous plants.

*The information shared in this article is for educational purposes only. While I strive to present accurate, evidence-based information, this content is not intended as medical advice, nor should it replace guidance from a qualified healthcare professional. Herbs, supplements, and natural products can affect everyone differently, may interact with medications, and are not appropriate for every individual. Always consult your physician, pharmacist or other qualified healthcare provider before using herbal products or making changes to your healthcare routine. Any discussions of poisonous plants, toxicology, or true crime are intended solely for education and historical exploration. Please never consume or handle wild plants without proper identification and appropriate knowledge.

The term ‘hemlock’ can refer to a few different plants.

Hemlock Tree

The first is the hemlock tree, or Tsuga. Hemlock trees are harmless conifers (a plant that produces cones) that belong to the pine family. They were named after poison hemlock by early settlers, because when you crush their needles, they smell like poison hemlock.

Hemlock trees are native to Asia and North America, and are what’s called a ‘foundation species’; a species that influences and shapes its ecosystem. Foundational species exist in large numbers, physically building the ecosystem they’re a part of and are usually at the bottom of the food chain, like trees, kelp or coral.

Hemlock trees are a vital part of their ecosystem as they:

Are important carbon sinks. They can live for hundreds of years and store massive amounts of carbon, helping mitigate climate change. (2)
Help protect watersheds. They have shallow roots, which helps stabilize soil, prevents erosion and filters pollutants. They also help prevent flooding during heavy rains by taking up excess water. (1)
Provide habitat. Their needles are a winter food source for moose and deer and birds love their oil rich seeds. (1)
Help control the climate in their environment. Hemlock trees cast the darkest shade of any northeastern conifer. This helps block out the hot summer sun, keeping the soil and streams they tower over cooler in the summer. This is vital for species like cold water fish, that require cooler temperatures to survive and reproduce. In the winter, their dense branches help trap heat and protects the ground from heavy snowfall. (3)

These trees are seen in several Indigenous stories as symbols of shelter, warmth and transformation. (16)

In the Seneca story Hótho and the Hunter, a hunter boasts to Hótho that the cold cannot freeze him. Hótho, who is cold personified, accepts the challenge and attempts to freeze the man, who stays warm by building a roaring fire and brewing a large kettle of restorative hemlock tea. (17)

In the Haida story, How Raven Brought Light to the World, Raven turns himself into a hemlock needle and is swallowed by a woman, where he then transforms into a baby in her belly. (18)

In The Haudenosaunee Creation story, hemlock is named as one of the trees created by The Good Spirit. (19)

Not only were hemlock trees important symbolic plants, they were also used in traditional Indigenous practices to treat colds, fever, foot odor, bleeding, arthritis, scurvy and even to prevent sunburn. (14) (15) Beyond medicinal uses, hemlock bark was valued as a source of dye, and the inner bark (cambium) was incorporated into foods such as bread and pemmican. (15)

Even after death, hemlock wood continues to support life, as decaying logs can provide a substrate for growing medicinal fungi such as reishi mushrooms. (13)

…

Water Hemlock

The second plant that shares the name hemlock is water hemlock, or Oenanthe crocata. Unlike the helpful hemlock tree, water hemlock is highly toxic and should never be touched with bare hands, much less ingested.

Native to Europe, this plant was introduced to North America, where it has since spread. It is often found growing in damp habitats, including ditches, riverbanks, and other areas where moisture collects.

Water hemlock can grow up to five feet tall, and produces clusters of small, white, umbrella-shaped flowers that bloom in July and release a sweet, fruity scent.

Beneath the soil, the roots grow in clusters of thick, white or pink tubers that resemble fingers, earning them the unsettling nickname “deadman’s fingers.” Despite their harmless appearance, these roots contain a powerful toxin, and even a single tuber contains enough poison to kill a cow. (4)

Unlike many poisonous plants that warn animals with bitter or unpleasant flavors, water hemlock does not taste harsh or burn. Instead, its roots have a surprisingly sweet taste, making them especially dangerous if mistaken for an edible plant. (6)

Ingesting this plant can lead to: (7)

Excessive drooling and sweating
Nausea, vomiting and diarrhea
Dilated pupils
Convulsions and seizures
Rhabdomyolysis (the rapid breakdown of skeletal muscle)
Kidney failure
Respiratory paralysis
Death

The deadly compound in water hemlock is called oenanthotoxin; a powerful neurotoxin found in especially high concentrations within the roots and stems. The stems can be easily mistaken for celery, while the roots resemble edible plants such as wild parsnip, leading to accidental ingestion. (5)

Oenanthotoxin is one of the most potent known convulsants and primarily affects the central nervous system, including the brain and spinal cord. It interferes with GABA; a neurotransmitter responsible for helping regulate and calm brain activity. By disrupting this calming signal, this toxin causes uncontrolled electrical activity in the brain, leading to severe seizures. (5)

The poison can also trigger powerful facial muscle contractions, causing the eyes to appear widened, the eyebrows to raise, and the lips to pull back into a disturbing expression. This condition is known as risus sardonicus, or a “sardonic smile,” because it looks as though someone is smiling or laughing despite being in distress. (4) (6)

In ancient Sardinia, a plant known as herba sardonica was associated with ritual death practices among the Punic people in the execution of individuals considered a burden to society, including elderly people who could no longer care for themselves and criminals.

According to some accounts of this tradition, the plant’s effects produced the aforementioned ‘grim smile’, suggesting that the herb used in these rituals may have been water hemlock. Some accounts suggest this expression held symbolic meaning, as the Punic people may have viewed death as the beginning of a new life and therefore something to be met with a smile. (4) (6)

…

Poison Hemlock

While water hemlock is considered one of the most acutely toxic plants in North America, it isn't the species that earned hemlock its infamous place in history.

The third plant of the hemlock name, and probably the most well-known, is poison hemlock, or Conium maculatum. This wildflower was originally native to Europe, North Africa, and western Asia, although it was introduced to North America in the 1800s as an ornamental plant. (10)

Identification

It grows 2 to 10 feet tall and has a long, hollow, hairless green stem mottled with red or purple spots. These are sometimes referred to as ‘the mark of Cain’, as legend says the purple spots represent the mark placed upon Cain’s brow after killing his brother. (8)

The flowers grow in umbels; small, white, umbrella-shaped clusters similar to Queen Anne’s lace, and it has triangular, finely divided leaves and a white taproot.

Like water hemlock, poison hemlock usually grows in moist areas such as stream banks, ditches and along roadsides.

Poison hemlock belongs to the carrot family, and is often misidentified as wild carrot, wild parsnip or wild parsley. It’s sometimes referred to as ‘poison parsley’ due to its similar appearance to the harmless herb. (20)

When the leaves or stem is crushed, it emits an unpleasant musty odor similar to the smell of mouse urine. This is because of the nitrogen-containing alkaloids found within the plant.

Like water hemlock, poison hemlock should not be handled with bare hands, nor should it be burned, as the toxins can be released into the air through smoke. (12)

Signs & Symptoms of Ingestion

From root to seed, every part of poison hemlock is toxic, with the seeds containing the highest concentration of harmful compounds. Its deadly effects come from alkaloids such as coniine, which interfere with the transmission of nerve impulses to muscles. This leads to ascending paralysis, where muscle function gradually fails, beginning in the legs and progressing upward toward the heart and lungs, causing death by paralyzing the respiratory system. (11) (20)

Symptoms can develop within 30 minutes of ingestion and include: (11) (9) (20)

Drowsiness
Trembling
Dilated pupils
Burning in the digestive tract
Excessive drooling
Nausea and vomiting
Rhabdomyolysis
Rapid heart rate followed by a decreased heart rate
Loss of speech
Convulsions and seizures
Coma
Death

Six leaves are enough to kill an adult, and even fewer seeds. (6) Just 100 grams of leaves is enough to poison livestock, but thankfully they tend to avoid its unpleasant odor.

Poison hemlock is usually ingested by accident. People may mistake it for carrot, parsnip, or parsley, consume contaminated meat or milk from livestock that grazed on it, or children may make whistles or flutes from its hollow stems.

Activated charcoal or gastrointestinal lavage may be used in an attempt to absorb the poison from the GI tract, but there is no antidote to hemlock poisoning, which is why it’s always best to avoid ingesting plants whose identity you’re not 100% sure of. (6) (20)

History & Folklore

While most cases of poisoning result from accidental ingestion, there was a time when poison hemlock was one of the preferred methods of state execution.

In ancient Greece, it was considered a more civilized and orderly form of capital punishment compared to alternatives such as decapitation.

This method of execution became closely associated with ancient Athens, where poison hemlock was used in several notable cases throughout history.

Theramenes was a controversial politician and general in Ancient Athens. He became a member of the Thirty (also known as the Thirty Tyrants); a harsh, pro-Spartan group of thirty oligarchs who ruled Athens from 404 - 403 BCE. (21) The Thirty were led by Critias, and during their brief rule, they executed an estimated 1,500 people, often without proper trials. (22) Theramenes opposed Critias' increasingly tyrannical rule. He advocated for a broader citizen body and condemned the execution and dispossession of innocent Athenians, leading Critias to brand him a traitor and have him executed. He was led through the marketplace and forced to drink hemlock. (23)

Theramenes was not the only prominent Athenian to meet his end through hemlock. Throughout Greek history, this method of execution became associated with several controversial political and philosophical figures.

Phocion was a respected Athenian statesman and general, as well as a student of Plato and close friend of the philosopher Xenocrates. After serving as a mercenary for Persia, he returned to Athens, where he supported the resistance to Macedonian expansion. As Macedonian power grew, he came to view military opposition as futile and instead advocated for diplomacy. Following the death of Alexander the Great, he was condemned on charges of treason by political opponents and forced to drink hemlock. The Athenians later acknowledged the injustice of his execution, and honored him with a public burial and a bronze statue. (24)

Perhaps the most famous death by hemlock is one of the most influential figures in Western philosophy; Socrates. Socrates was executed in Athens in 399 BCE after being found guilty of impiety and corrupting the youth. While those were the official charges, many historians believe the real reason was political: several of his former students, including Critias, had helped overthrow Athenian democracy and rule as brutal tyrants. Although Socrates never took part in their crimes, his criticism of democracy and his association with these men made many Athenians view him as a dangerous influence. After refusing to plead for mercy or compromise his beliefs, he was sentenced to die by drinking a cup of poison hemlock. (25)

While hemlock became infamous through its role in ancient executions, its association with death and altered states continued into European folklore and magical traditions.

Aside from killing ancient philosophers and politicians, it has been used by practitioners of magic in spells designed to paralyze a person or situation, and in flying ointment. (9) For those unfamiliar with the term, flying ointment refers to an herbal salve historically associated with European witchcraft and beliefs surrounding altered states and spiritual travel. These preparations were said to help the user experience sensations of leaving the body or traveling beyond the physical world.

Flying ointments contained toxic plants, such as hemlock, belladonna, henbane and mandrake. These herbs were mixed with animal fat and applied topically. Absorbing the compounds through the skin was thought to be a safer route than ingesting them orally, and led to hallucinations, altered perception and feelings of weightlessness or flying. It’s important to note that these plants are still toxic, even when rubbed on the skin, and could still lead to total poisoning and death.

Sources

poisonous plants

Floris Obscura