What it takes to tend the world’s deadliest garden
A toxic tour of the high-security facility with more than a hundred plants that could kill you.
The keepers of a poison garden on the grounds next to Alnwick Castle in Northumberland, England, anticipate a great many fainters every year. The garden, the largest of its kind, sits behind stately iron gates embellished with skulls and is packed with more than a hundred varieties of plants so deadly that you can’t enter without supervision.
As tours set off, guides warn visitors not to touch, lick, or pick as they learn about poisoners from history and see the brews and cuttings that served as their weapons of choice. There’s the Teacup Poisoner, who kicked off his infamous murder spree by dosing his sister with Atropa belladonna. And Doctor Death, a physician convicted of murdering 15 of his patients with a drug derived from the opium poppy. Every so often—crunch!—another guest hits the gravel. Gardeners attribute the uptick in faintings to all the macabre stories. Might it also be possible that some blended emanation from the plants, the heady perfume of oleander, yew, and nightshade, combines to sweep the more susceptible off their feet?
The poison garden, which opened 20 years ago as a ghoulish attraction, has taken on new life moonlighting as a destination for researchers of all kinds, from scientists curious about exotic toxins to crime writers looking for inspiration. One summer day, when the annual faint count was at about 70, Mikey Leach, the 38-year-old head gardener, cracked open a glossy laurel leaf protruding across a path. “This is one of the most common hedging plants in this country,” he said. “Cut it open? Cyanide.”
Alnwick Castle has belonged to one English family for over 700 years. Traditionally the seat of the region’s highest ranking aristocrat, the castle and the adjacent garden’s 42 acres have been passed down through various earls and dukes to the current owner, Ralph Percy, the 12th Duke of Northumberland, who moved in in the mid-1990s with his wife, Jane. The duchess set about improving the dilapidated property, adding fountains, mazes, and sweeping lawns—and creating a charitable entity called the Alnwick Garden, which includes the poison garden.
While some of the most destructive plants here are also sources of medicinal cures and antidotes—like Madagascar periwinkle, which can cause liver toxicity when ingested but is also used in leukemia treatment—the benefits neither inspire nor impress the duchess, who once said, “The story of how plants can cure I find pretty boring, really—much better to know how a plant kills.”
The ubiquity of poison in our own backyards motivated a group of forensic chemists to conduct a year-long experiment in the garden quantifying toxins in 25 different plants that have been accidentally ingested by children. Atropa belladonna, used by the Teacup Poisoner, was one of the most hazardous to kids, the scientists determined, and better public awareness was needed to prevent further fatal consequences.
Back in the gardeners’ break room, a whiteboard listed that day’s jobs: Cut the grass along an access road; tend to 20 lethal mandrakes. “Mandragora, so entwined in human history,” said Leach, who went on to explain that pharaohs used Mandragora as an intoxicant, and Romans as a battlefield anesthetic. More recently, the Harry Potter books made squealing, sentient mandrakes a source of color, with magical roots resembling crying human babies.
Leach only started reading up on Mandragora this spring, he confessed, after receiving an email from a mandrake enthusiast who wanted to give Alnwick her collection, which included a rare varietal native to the mountains of Central Asia. The 20 inherited mandrakes now live in a covered facility by the break room. “It’s the roots that are super poisonous,” Leach said. “We’re going to have to cage them.”
Caged plants, being the most vicious, draw the greatest interest. Some Ricinus communis, producer of the poison ricin, are kept caged. But an innocuous-looking green and purple plant must be, by law. “Salvia divinorum,” Leach said. “You smoke it, and you go on an acid-like high for 30 seconds.”
It’s clear why mystery writers like coming to Alnwick. The first time British novelist Jill Johnson visited, she explored the nettled lanes, her hands tucked nervously in her pockets. Then, the initial stirrings of an idea: a botanist-detective who uses her garden as a crime-solving tool, similar to Agatha Christie’s beloved Miss Marple character. Johnson’s first book in the Professor Eustacia Rose Mysteries, Devil’s Breath, came out in 2023, and since then she’s returned to Alnwick for inspiration. It’s “an incredible goody bag full of poisonous wonders,” she said, “that will keep me inspired to murder more people, using more lethal plants, for a very long time to come.”
According to staff at the Alnwick Garden, at least one real-life police force has inquired about visiting to “discuss the use of plants and poisons that might be appearing on a watch list—ones to keep their eye out for in the future.” The police force in question declined to comment, but there have been several high-profile poisoning cases in the United Kingdom, famous among them the 2009 murder of a man whose curry dinner was laced with wolfsbane. Leach pointed out that it would take just a nail-clipping-size piece of mandrake root to put somebody in the ground. Better for everyone, it seemed, if detectives knew their marsh marigold from their mistletoe.
The garden constantly incorporates new plants, but up until recently it was missing one of the world’s most painful species. The Dendrocnide moroides, or “gympie-gympie,” is an incredibly dangerous Australian stinging nettle, and even a slight brush with it can make you vomit. After watching YouTube videos of the plant’s victims, head tour guide John Knox tried growing one from a seed he bought online; when that failed, he contacted a man he’d read about who kept one the size of a garden gnome inside a birdcage in his living room. Knox transported it to Alnwick in a dog cage covered with trash bags to avoid coming in contact with the spindles, which can create an effect he described as “like being set on fire, and being electrocuted, and having hot acid poured on you, all at the same time.”
The gympie-gympie, now several feet larger, lives Lecter-like in a clear locked box at the far end of the garden. “We don’t open it without a hazmat suit,” Leach explained. “Imagine if a gust of wind blew in!” Like Knox, Leach had done his research. “Three or four weeks of sheer pain. Flare-ups for the next few years,” he reported. “It’s a thing of nightmares. And how do you manage a collection that contains nightmares?” He had started gardening when he was a small boy, drawn to it, he said, because it was just about the least scary thing he could imagine doing. And look where he ended up.
(The poison fruit from ‘The White Lotus’ is real—and it attacks the heart.)
The poison garden is next to Alnwick Castle in Northumberland. Tours cost around $30 for adults and occur every 30 minutes during opening hours, which vary seasonally.
