Northumberland garden where every single plant is toxic - and some of them can kill you

At the Alnwick Garden, the air is thick with the sound of lawnmowers giving the already-neatly manicured grass a final once over before a busy summer's day. The Grand Cascade sits silent, its 120 fountains dozing ahead of shooting water into the skies every half an hour.

But I'm not here for the fancy fountain shows or to wander round the rose garden, but instead for what sounds like one of Northumberland's darkest and most sinister attractions - The Poison Garden. Any scary image is instantly undermined by a brace of ducks and their newly-hatched ducklings pottering around on the lawn outside.

"I've just fed them, they're practically tame," guide Dean Smith says, against the backdrop of black, wrought-iron gates marked with a skull and the phrase "these plants can kill".

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First established in 2005 by the Duchess of Northumberland, the second phase of the Poison Garden was opened officially by the then-Prince Charles in 2007. It is home to more than 100 toxic plants, and every single one can do you some serious damage - even common household plants and foodstuffs such as rosemary and rhubarb.

Dean finishes feeding the ducks, and explains that the garden is to educate children on the dangers of drug abuse, subtly. He says: Make it into a herb garden, you lose kids immediately.

"Tell them the plants can kill them and they're fascinated. And the by-product is, you get to find out how poisonous your garden and your plants are."

Everyone is given a safety briefing before entering, with the warning "no touching, no sniffing, and definitely no salads". If you misbehave, you'll be asked to leave - or even worse, Dean will show pictures of giant hogweed burns and tapeworms in the folder he carries around to assist on the tour.

Nettles are an underwhelming start, and rhubarb feels like it shouldn't be there at all - until you find out the leaves are packed with oxalic acid, used in paint stripper and engine de-greaser. That's also in dock leaves, with Dean recommending against their use to treat nettle stings, and instead going for an antihistamine or a mixture of toothpaste and water.

We move on to more exotic plants than what you'd find in your average British garden or riverside. The summer holidays are the garden's busiest time, and exotic and tropical plants which reside in polytunnels for the rest of the year are on display in the garden - albeit caged.

I'm introduced to khat, a leaf used as a "social lubricant" in Somalia and Yemen which has carcinogenic leaves; oleander, where four leaves are enough to kill you; and the castor bean plant, where one bean can kill you and several of your mates too. There's also angel's trumpet, which can rob you of short term memory and leaves you "compliant to suggestion" and one of the garden's newest additions, strychnine, which if you eat it can tear muscle from bone.

There's even one plant that is so dangerous it's kept in a padlocked glass case - the Gympie Gympie. Introduced to the garden last year, the stinging tree is loaded with spines which inject a neurotoxin into your bloodstream, causing a pain described as "hot acid poured upon you as you're being electrocuted and set on fire at the same time". I wonder who told them about that.

But why are these plants so dangerous? According to Dean: "All they're doing is defending themselves, they're not out to get you.

"First, there were just plants. Then along came animals, and they wanted to eat them.

"The plants built up their defences, but animals became resistant, so the defences just become more and more potent. That's how we end up with something like the Gympie Gympie."

There's more to see, including Britain's two most poisonous trees, the yew and laburnum, and plants such as the deadly nightshade, which can be found in the great British countryside. But it's the Gympie Gympie and its startling effects that continue to dominate my thoughts after I leave.

The fact that I've walked out without any issues isn't something everyone manages - of the roughly 80,000 who visit annually, 147 fainted in 2023. That figure stands at 64 for 2024 at the time of writing, with 30 of those in July alone.

Anneka Thompson, another Poison Garden guide says: "People faint because they go through the gates and when they get in, we tell them about plants from their garden and all the ways they can harm them. For some people, that's too much - and those who don't faint vomit."

A chalkboard with last year's figures on showed that as well as the faints, six people vomited and one even left in an ambulance. But it's not all bad, there were three proposals too.

Such a strong reaction could lie in the creation of such a foreboding environment - in reality, there's almost zero chance you'll come to any harm in the garden. The tour is entertaining, engaging, and it's clear that the guides put a lot of thought into the research and storytelling.

Dean finishes: ""If there's one piece of information I'd give to any of your readers, it's to always wear gardening gloves, and not to remove them with their teeth!"

"This is my sixth year in the garden, it's fascinating. We do lots of research because we constantly want to keep our stories fresh for the public.

"You meet people from all over the world because there are so few poison gardens in the world. A lot of the people who come want to tick it off their bucket list."

As I leave, people are starting to queue up for the first tour of the day at 9.30am. Claudia and her family are on a three-week sightseeing trip of the UK from Germany, and are on their way to the Scottish Highlands from London.

They have made a diversion to Alnwick especially for the Poison Garden after her eldest daughter saw it online. Will they make it out without fainting? Let's hope so.

Alnwick Garden is open 9am - 6pm throughout the school holidays between July 20 and September 1. Adult tickets are £16.50 and up to four children can join them free of charge, with "The School of Poison" on especially for kids during the holidays.