Perfectly Poisonous: Plant at your own risk!
Written by Ilona Biro, FOAG Volunteer
At Halloween, it seemed fitting to have a brief look at some of the most poisonous plants, one of which lives in our own Allan Gardens conservatory.
While the very word “poison” conjures up images of deadly dinner parties in Agatha Christie novels, poisonings still occur and sometimes make the news. Modern day versions are usually inorganic or synthetic, like the nerve agent Novichok used on Putin critic Alexei Navalny in August. Go back a few centuries however, and the story of poison is the story of plants, often entwined with some of the most classical and romantic of legends.
Scientifically, toxic compounds that may be found in plants often originate as secondary metabolites, not essential for plant life. Some of these compounds we use every day, like caffeine and theobromine, while other plants produce highly toxic secondary metabolites which people have used for centuries to silence an unwanted voice, or as a form of execution.
During the reign of Emperor Nero, the professional poisoner Lucasta – really, a serial killer – was said to have poisoned thousands of his enemies. Centuries later, in Renaissance Italy, poisoning was at its height. Prepared by physicians, alchemists, and pharmacists, poisons were employed by wealthy families like the Borgias, under the impulse of lust and avarice for power. Murder in political circles became so frequent that nobody believed in the natural death of popes, cardinals, and royalty. Many of these poisons originated from the so-called “three kingdoms of nature” (animals, plants, and minerals) and included snake venom, cantharides, aconite, belladonna, strychnine, corrosive sublimate, arsenic, and others.
Nerium oleander – photo credit – user: Alvesgaspar/Wikimedia Commons/Public Domain
Knowledge of poisons was passed down, often by women, and many a Roman wife used the easy way out of marriage by poisoning her husband with oleander (Nerium oleander), a common shrub in Roman gardens.
Here are a few of the most notorious poisonous plants, along with an example or two of where they appeared in history or literature.
Angel’s Trumpet (Brugmansia sp.)
Angel’s trumpet – photo credit – Diana Teal
We’ll start with one of the showstoppers at Allan Gardens, the massive angel’s trumpet plants which visitors rarely miss. Also called trumpet of death, its blooms are attractive and widely cultivated as a flowering ornamental, but all parts of the plant are highly toxic. Many cultures use Brugmansia in their shamanic ceremonies, for sedating prisoners and calming unruly children. But because of its toxicity and the inherent dangers of ingestion, typically it has been used topically as a poultice, tincture or ointment applied directly to the skin. Best to stay well away!
In the news: The hallucinogenic effects of Brugmansia were described in the journal Pathology as “terrifying rather than pleasurable”, yet its hallucinogenic properties tempt many to try it. One unfortunate case reported in neuroscience literature involved a young man performing self-amputation with pruning shears after intentionally ingesting Brugmansia tea, boiled from just two flowers. In 1994, 112 people in Florida were admitted to hospital after ingesting it, prompting one municipality to ban the cultivation and sale of Brugmansia plants.
Deadly Nightshade (Atropa belladonna)
Deadly nightshade – photo credit – user: Agnieszka Kwiecień/Wikimedia Commons/Public Domain
The alkaloid Atropine is one of the active ingredients in deadly nightshade. Atropine is used during surgery to regulate the heartbeat, decrease salivation, and paralyze muscles. In eye surgery, it relaxes the muscles and dilates the eye. The eye dilation is said to render even plain janes much more beautiful, which is how it got its name, bella donna, or beautiful woman.
Famous mention: In Shakespeare’s Macbeth, Lord Macbeth uses nightshade to slow down a Danish army that was preparing to invade Scotland.
Poison Hemlock (Conium maculatum)
Poison hemlock – photo credit – user: Sylvain Piry/Wikimedia Commons/Public Domain
Poison hemlock is a flowering plant with fleshy, carrot like roots that can grow up to ten feet tall. Not to be confused with the hemlock tree, all parts of the poison hemlock plant contain poison alkaloids. If ingested, conium will cause paralysis of various body systems, though it is paralysis of the respiratory system that is the usual cause of death. Meanwhile, a victim can’t move but is aware of what is happening as the mind is unaffected until death is imminent. Really unpleasant!
Famous usage: Socrates was 70 when he was found guilty of heresy in 399 BC. His sentence was death by hemlock which he had to drink by his own hand. He did so and afterward walked around until his legs felt heavy. He was surrounded by students and adherents when he died, a scene captured by the painter Jacques-Louis David.
Castor oil plant (Ricinus communis)
Castor oil plant – photo credit – user: Blmurch/Wikimedia Commons/Public Domain
According to the Guinness World Book of Records, this is the world’s most poisonous common plant. The poison Ricin is derived from the castor oil plant and is less toxic than anthrax, but thousands of times stronger than cyanide or rattlesnake venom. It has a long history of being associated with political assassinations, and the dreaded castor oil that children were given also has a history of involvement in political threats and punishments. Poisoning occurs when animals, including humans, ingest broken castor beans or break the seed by chewing: intact seeds may pass through the digestive tract without releasing the toxin.
Famous usage: Mystery writer Agatha Christie was incredibly well-informed about poisonous plants, and poisonings were a common plot device in many of her bestselling novels. Not only did she grow many in her own garden at Greenway, Christie also worked in a pharmacy during both world wars, and was intimately familiar with the ill effects of poisons which she used to great effect.
