Friday essay: cure or kill? The deadly serious world of poison gardens – and why I planted my own

Not every plant is your friend. Not every plant is good. I know this because I’ve been researching the history of poison gardens and have planted a modest one in my small Sydney backyard.

A poison garden contains only toxic plants, which could kill humans if consumed in varying quantities. The concept of a poison garden grew from the 16th to 17th century history of herbalist or apothecary gardens, where plants and herbs were grown for medicinal purposes, mostly by doctors and monks.

These early gardens flourished at a time when herbals, hefty reference books on medicinal plants, were produced. An example is John Gerard’s 1500-page book The Herball (1597), which included English plants and herbs but also exotics collected from the “new world” (colonised countries such as the Caribbean islands). Within these apothecary medicinal gardens, specialist planting areas were sometimes allocated to exotic carnivorous, aquatic or poisonous plants.

Italy’s Padua Botanical Garden, dating to 1545, includes poisonous plants. Such gardens were established for reasons of natural history, botanical education and medicine but also as places of spectacle or intrigue. And there was a lot of intrigue in 16th and 17th century Italy and France, with flourishing small poisons businesses, usually run by women. Catherine Monvoisin, for instance, had a thriving consultancy as a poison supplier in Paris, until she was tried for providing lethal poisons in a murder plot and executed in 1680.

Most poisonous plants have qualities of cure and of medicinal care … but they are also dangerous. This is what Greek philosopher Plato called pharmakon – the idea that plants can cure, but they can also kill if the dose is high enough. The trick is knowing those thresholds.

To honour the medieval tradition, my poison garden is planted in a circular, raised garden bed, hip-height. There is, of course, nothing illegal about growing plants that contain high levels of poison compounds. Poisonous plants are potted up in many living rooms and suburban backyards.

Bunnings sells Dieffenbachia (known as dumbcane) as indoor plants. But eating their leaves can swell your tongue and limit speech, they can even cause death by asphyxiation if too much is eaten. Plant stores sell azaleas like they’re going out of fashion but all parts of the plant can cause nausea and vomiting if eaten, and death if too much is ingested. I have both plants at home.

In my designated poison garden, the centrepiece is the brugmansia (also known as angel’s trumpet), a leafy shrub of the nightshade family with with exquisite hanging trumpet-shaped flowers.

Its cousin, the datura, is known as the devil’s trumpet. Brugmansia stimulates psychoactive hallucinations if eaten. Its seeds and leaves are potentially poisonous and can cause confusion, fast heart beats, paralysis, tremors and even death.

Henbane is another highly toxic nightshade, with holly-green leaves. Mine hasn’t flowered yet but, in small doses, it relieves vomiting. My mugwort has leaves almost like continental parsley and in small amounts can treat menstrual and digestive complaints.

Hellebore is commonly grown as public landscaping across Australian cities because it is hardy and has gorgeous purple and deep red flowers. Hellebore has been said to treat mental health but can cause toxicity if too much is taken. My hellebore has creamy flowers. Finally, I have wormwood, which deters mosquitoes with its poisonous oils.

I’m interested to see how these poisonous plants might flourish together in one garden bed. The poison garden is intended to remind myself, family and friends that plants are not always “good” and deserve absolute respect, with a pinch of fear.

The world’s most toxic garden

The Duchess of Northumberland, Jane Percy, understands poisons. She has built the world’s most renowned poison garden. Her garden, at Alnwick Castle on the north-east coast of England, hosts plants that kill. This extreme poison garden, with locked gates, round-the-clock security and tours conducted by guards, receives hundreds of thousands of visitors each year.

The duchess has around 100 toxic plants, including hemlock and foxglove, which has fine hairs that cause painful rashes, and hogweed, which can burn human skin.

She has deadly nightshade, which looks like honeysuckle but has shiny black berries that can be fatal if consumed. Wolfsbane, with its pretty purple flowers sprouting up and down the stem, is one of the most lethal plants in her garden and can kill you (its toxic roots affect the human heart and nervous system, if eaten). Perhaps the most poisonous plant is ricin, also known as the castor bean or castor oil plant. She also has cannabis, which she needed a permit to grow. The cannabis plants are securely caged and padlocked.

I met the duchess in mid-August. She had just bought her very first Australian poison plant to add to her collection. It is gympie gympie, known as the “suicide plant” because it causes such awful skin itch and intolerable pain.

The duchess and I discussed the cure/kill paradox. Many people think consuming plants can only be healthy, virtuous and good for you. But most plants are potent, few are completely benign, and if you get the wrong dose, you can become very sick or even die.

One day, she tells me, around 30 people fainted in her poison garden due to the henbane.

“You can’t sniff henbane when it’s in full flower because it can make you faint. And we have a big bench in the poison garden [where people sit], sometimes you’ll go in and find someone out for the count.”

I love the duchess’ candour. As humans, we think we have plants under control, especially in our constructed gardens. But plants have different ideas.

Women have been closely connected with plants through the millennia. It was women who historically ran the domestic kitchens and gardens, other than the odd male apothecary. Not to mention the vast swathe of First Nations women herbalists across time. Only those traditional women really knew the limits of plant compounds, the tipping point.

Across France, during the early 16th and 17th centuries, there was an epidemic of poisoning for power, revenge and money. The famous Affair of the Poisons during the late 1600s was a murder scandal among the aristocracy during the reign of French King Louis XIV. Thirty-six people, mostly women, were charged with poisoning – including Catherine Monvoisin – and subsequently executed.

Italy also has a history of plant poisoners. The first century Roman poison-maker, Locusta, was known to use Atropa belladonna as her poison of choice, learning her skills from Empress Agrippina the Younger. These doses were not always intended to kill, but to cause her victims to suffer.

The powerful Italian apothecarist Caterina Sforza (1463–1509) first discovered chloroform. She is known for her invisible inks, recipes to whiten skin and to dye hair black, and a poison made of distilled scorpions. Sforza also grew an apothecary garden in Ravaldino and worked the herbs with the advice of her own personal apothecary assistant, Lodovico Albertini. She was accused of poisoning the pope but later exonerated.

In Sweden, similar activities were at play with Queen Christina of Sweden (1629–1662) who employed a poisoner, Nicolo Egidi, known as Exili, who had knowledge of poisonous plants and of alchemy.

The Duchess of Northumberland has no such malign purposes. When she started the garden in 1995, she wanted to make something a bit different. She thought, “OK let’s do kill rather than cure”. Her approach is one of educating people about plants’ different capacities.

Before she designed her garden, the duchess travelled to Padua to see the famous world-class apothecary garden the Medici family built in 1545. This garden, still open to the public and now a world heritage site, is the oldest botanical garden in the world.

Her poison garden shares information about the darker side of plants. Drug safety groups educate young visitors on the toxicology and harm of plants, including drugs such as cannabis and opium.

The day-to-day operation of a poison garden is not trivial. Hers has security systems, cameras and guards. Some of the beds are gardened by staff wearing full hazmat suits. There is a skull and crossbone symbol on the entrance gate. “You have to police it,” says the Duchess. “You can’t just let people roam around. And we tell the stories of how the plants kill.”

Though in truth, she says, “the plant doesn’t kill without man’s intervention, usually”.

At 66, the duchess, who insists on being called “just Jane”, looks almost fairy-like, with flawless English skin. Today, she spends half her time near Soutra Aisle in Scotland. Soutra Aisle was an old hospital town where, during the Middle Ages, soporific sponges – laced with henbane, opium and hemlock – were used to anaesthetise patients. The rest of the time she stays at Alnwick Castle.

Matriarchal knowledge

There is also a poison garden at the Blarney Castle in Ireland. Australia does not boast any public poison gardens but Felicity McDonald runs a witches’ garden in the Mitta Valley, Victoria. Although it is not a poison garden, Felicity does have a lot of poisonous plants – hemlock, wormwood, hellebore, hogweed, datura, rhubarb, hydrangeas, foxglove, yew and more.

McDonald stresses poisonous plants should only be accessed under supervision. “Being a witch’s garden, we have plants that heal, however some of these plants have contradictions which could make you very sick or result in death.” She guides groups around the garden – school groups, senior citizens, families and Wiccans (people who follow pagan rituals and crafts) – describing plants’ medicinal and poisonous qualities.

I ask McDonald if there is a matriarchal knowledge associated with women and plants, especially poisonous ones. Yes, she says, and it is all about control. Reducing a woman to home duties, she says, denied her power. “But ancient Egyptians worshipped Isis, goddess of healing and magic. In Celtic Britain, the goddess Brigid was responsible for healing, poetry and smithcraft. And in Norse countries, Eir was the goddess associated with medical skill.” So while women had little influence in the public political sphere, they exercised power in the realms of herbs and healing.

McDonald notes that even the humble hydrangea is highly poisonous. The leaves and flowers contain cyanide and can cause vomiting and nausea if consumed by humans and pets.

Both McDonald and the duchess note the number of women with traditional expert plant knowledge has declined over recent centuries. I ask the duchess whether she mourns this loss of plant-related matriarchy. She answers, “A matriarch implies a strong woman who is a leader but often the best poisoners were acting quietly behind the scenes; tending to their gardens; weeding, drying herbs.”

People are scared of poisonous plants. To some extent, for good reason. But I’ve been surprised by friends’ responses to my new poison garden. They react as though I’ve really and truly gone too far this time.

I have only five poisonous plants in it and they are all benign … so long as they are not eaten in any way or touched with bare hands. It would not be wise to drink even a single drop of the flower nectar. I have other hallucinatory plants in the wider garden that can also work as cures if taken mildly, but are potentially poisonous if taken in large quantities. I have sourced some plants from friends, some from rare garden suppliers who sell “ceremonial” plants and some from my local garden store. None of these are illegal or part of an underground network.

It’s important to remember that there are poisonous plants all around us – hydrangeas, oleander, rhubarb, daffodils. You need a permit, security and insurance to have a poison garden that is open to the public. My garden is private and carefully signposted, so it is no more illegal than my neighbour’s daffodils or the hellebore growing in the council landscaping across the road.

Still, I recently experienced a pounding headache, a slight racing of the heart and nausea. I remembered I’d been pulling dead leaves off my poison plants (I hate wearing garden gloves) and had forgotten to wash my hands when I came inside. I’m pretty sure they made me sick. It’s a reminder to take care, because plants are serious.

Prudence Gibson, Lecturer and researcher in Plant Humanities, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.