Correction: An earlier version of this story implied that the Alnwick Garden is on the grounds of Alnwick Castle. While the Duchess of Northumberland did set up the garden and lives at Alnwick Castle, the two are separate entities.

“Don’t touch,” says Bridget the guide, as we prepare to enter the locked gates of the Poison Garden. “Don’t smell.”

Don’t worry: I had seen the skull and crossbones on the black wrought-iron gate, right next to the sign proclaiming “These Plants Can Kill,” and I plan to give them a wide berth.

Bridget tells us that no one has actually died from visiting the Alnwick Garden’s Poison Garden, but people have fainted, possibly because they ignored the no-touch, no-sniff rule. There’s hemlock and deadly nightshade everywhere. Those pretty foxgloves, pink as a baby’s cheeks, can cause vomiting, hallucinations, madness. Oleander, the same kind that grows from Washington all the way down to Key West, can cause nasty rashes and wreak havoc on your central nervous system. Laurels contain cyanolipids that release cyanide and benzaldehyde, especially when cut.

The adjacent Alnwick Castle is a vast stone edifice strategically located on the River Aln, not far from the Scottish border. If you’ve seen the first two “Harry Potter” movies, you’ve seen Alnwick: Harry learned to fly a broom and play Quidditch in the castle’s Outer Bailey. It was also the setting for the Season 5 finale of “Downton Abbey.” Parts of it are nearly 1,000 years old and stuffed with Titians and van Dykes, Louis XIV furniture, Meissen china and Georgian silver.



The Grand Cascade water feature at Alnwick Castle, in northeast England. (Rebecca Jenkins/for The Washington Post)

I’d been staying in Barnard Castle, a lovely market town on the River Tees, about an hour and a half’s drive to the south, seeing friends. They kept asking whether I’d been to the Poison Garden — apparently, it’s notorious in these parts. Other parts, too. So I drove up over the moors, dodging death-wishing sheep (they like to lick the salt on the road), north of Hadrian’s Wall to Alnwick. Because I had limited time, I decided to save the castle for another day and concentrate on the gardens: How often do you get to keep company with plants that can produce heroin, cocaine and ricin, one of the deadliest toxins on earth?

The Poison Garden tours go every 15 minutes, and I have a few minutes to wait for the next one. Next to the locked gate, there’s a hut, kind of a cross between a prehistoric dwelling and a hobbit house, round with a sod roof. I stick my head in the door, half expecting to find a homage to “Harry Potter” or an animatronic witch. Instead of hokey horror, the place is full of animals — dead animals. Stuffed ravens, stuffed foxes, stuffed rabbits, their glassy eyes flickering in the firelight. A stuffed gray-and-white cat holds a stuffed rat in its mouth. Other stuffed rats perch on shelves. The back half of a hare is mounted on one wall over a pile of unidentified pelts.



Daffodils and hemlock envelop a wooden “skeleton” and Cannabis sativa — marijuana — grows in a cage behind it at the Poison Garden, dedicated to plants that are fatal or narcotic. (Rebecca Jenkins/for The Washington Post)

“Oh, yes,” says a voice behind me. “The Duchess loves taxidermy.” It’s Bridget, who is gathering up the tour. It seems the Duchess of Northumberland, chatelaine of Alnwick and creator of the Poison Garden, keeps several stuffed dogs up at the castle. She sometimes gives stuffed rats as wedding presents.

Perhaps I should explain about the duchess, the brains behind it all. She was plain Jane Richard before she married Ralph Percy, younger brother of the 11th Duke of Northumberland, in 1979. In 1995, the childless 11th duke died of an amphetamine overdose, and Ralph became the 12th duke, owner of Alnwick Castle. The new duchess decided to throw herself into renovating the castle’s once-beautiful landscaping. The old formal gardens had fallen into ruin. Much of the land next to the castle was used for lumber. Within a few years, however, what had been 14 acres of commercial spruce trees was transformed, thanks to the duchess, Belgian garden designers Jacques and Peter Wirtz (who’d redone the gardens at the Élysée Palace in Paris) and upwards of $60 million.

Where there was wasteland there’s now The Alnwick Garden, which includes a bamboo labyrinth, 3,000 roses, tunnels of green vines, bright tulips, flowering cherries and delphiniums in their own formal walled garden, sculptures that double as fountains and one of the largest treehouses in the world. When you get tired of walking, you can sit outside on the contemporary glass pavilion, watching the monumental cascade, Alnwick’s modern answer to the baroque water features of Versailles or Peter the Great’s Peterhof Palace.

The style and expense of the gardens has been controversial. The Percy family is estimated to be worth nearly $1 billion, yet the duchess received some taxpayer money for her project. When the new Alnwick gardens opened, another aristocratic gardener, Lady Mary Keen, whose father is an earl, accused the duchess of “vanity gardening” and called Alnwick vulgar. The duchess hit back at her critics, calling them “snobby” and worse, and pointing out that the gardens bring needed revenue and jobs to an economically depressed area.

The Percys have always reveled in being troublemakers: a 15th-century Percy rebelled against King Henry IV — William Shakespeare immortalized him as “Harry Hotspur.” In the 16th century, a Percy led the lords of the north against Elizabeth I, hoping to replace her on the throne with Mary, Queen of Scots. He was beheaded in 1572. You’d think the Percys had learned their lesson, but no: In 1605, a Percy plotted with Guy Fawkes to blow up Parliament. A little closer to home, in 1829, another member of the Percy family, the illegitimate son of the 1st Duke of Northumberland, left his large fortune to the United States government to promote “the increase and diffusion of knowledge.” You know it as the Smithsonian Institution.



White daffodils in a wooden “skeleton.” Roman soldiers used to carry daffodil bulbs, which are toxic, to commit suicide with if they were captured. (Rebecca Jenkins/for The Washington Post)

There was an outcry in 2005, too, when the duchess opened her Poison Garden. Inspired, she said, by a 450-year-old “physick garden” in Padua, in northern Italy, reportedly used by the Medicis to dispatch their enemies, the duchess had to get a government license to grow the plants that are converted to cocaine, psilocybin mushrooms and marijuana “for educational purposes.” Since the 11th duke struggled with addiction, it’s hardly surprising that when Bridget the guide herds us to where some young (but vigorous) Cannabis sativa grows, firmly locked in a cage, she launches into a lecture on how weed is now “60 percent stronger” than it was 30 years ago and causes major developmental damage in the brains of the young.

A couple in our group, 60-somethings, glance at each other, clearly not buying it.

But the weirdest thing about the Poison Garden isn’t the exotic stuff. Not the coca plant (from which cocaine is derived); not Artemisia absinthium, from which you make van Gogh’s favorite tipple, absinthe — it makes the color yellow look much, much stronger than it is, which may explain those sunflowers. No, it’s the ordinary plants that turn out to have dark souls. Like daffodils. Did you know ingesting a bulb will hospitalize, if not kill you? Roman soldiers used to carry daffodfil bulbs with them to war in case they were captured and needed to commit suicide, the guide says. Or periwinkles (or vinca, or “sorcerers’ violet,” as they call it in the wilds of Northumberland). It was used in love potions, but too much would crash your blood pressure. And catnip — you know, weed for your feline? The hangman would eat a bunch of it when he was due to execute somebody. Apparently it makes humans mean, quarrelsome and violent.

Many gardens in the American South have Angel’s Trumpet, Brugmansia suaveolens, growing all over the place, probably assuming, as the Poison Garden Web site says, “its common name refers to the look of the flowers rather than the indication that this is the sound to be heard after ingestion of a fatal amount.” It’s a strong aphrodisiac and a hallucinogen: Victorian ladies would put a little of its pollen in their tea and trip happily away. Too much and, well, they tripped all the way into the grave.

The Poison Garden is enough to make a normal person paranoid . . . make you think you feel kind of funny. Maybe the wind blew something onto your skin or into your mouth. And what about the other people on the tour: Are they mere tourists? What if they’re psychopaths? I ask Bridget one last question, about a nice-looking plant with purple-y flowers labeled Aconitum napellus. “That’s monks-hood,” she says. “Also called wolfbane.” She tells us the story of a “jilted girl” in London who murdered her ex-boyfriend in 2010. She put wolfsbane in his curry. The strong spices disguised the poison, so he never knew what hit him.

Right, I think. That’s it. I need a drink. I make my way across the rope bridges to the Treehouse, a bar and restaurant perched high in some lime trees. The Treehouse is famous for its cocktails: nettle and jalapeño martinis, and concoctions named, weirdly, for the duchess herself: the Dirty Jane is vodka and raspberry liqueur; the Deadly Jane is dark rum and white rum with apricot brandy, orange and pineapple juice and grenadine. What are they trying to do, kill me?

I go for the Desirable Jane, basically a mojito, with Bacardi, lime, mint and soda. When it arrives, I say to the waitress, “You’re sure that’s just mint.” She promises me it is.

I eye it suspiciously: You can’t be too careful around here.

Roberts teaches writing at Florida State University in Tallahassee. Her book “Tribal: College Football and the Secret Heart of America,” will be published in October.

More from Travel:

Travel Guide

Ski Guide

Caribbean Guide