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Plants as beautiful as they are toxic: poinsettia, ivy, yew, oleander...

Plants as beautiful as they are toxic: poinsettia, ivy, yew, oleander...

The 'Poison Garden', located in Alnwick Castle, in the English county of Northumberland, houses around 100 poisonous, intoxicating and narcotic plants, and visitors are strictly forbidden to smell, touch or taste them

Elena Martín López

Friday, 1 March 2024, 12:31

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The sign at the entrance is clear: "These plants can kill." And the skull and crossbones that illustrate it leave no room for doubt. This is the sign that guards the deadliest garden in the world, the 'Poison Garden', located in Alnwick Castle, in the English county of Northumberland.

It houses around 100 poisonous, intoxicating and narcotic plants, and visitors are strictly forbidden to smell, touch or taste them. However, despite the risk, the morbid curiosity aroused by the deadliness of this place has made it one of the most visited tourist attractions in the country.

"Some people occasionally faint from inhaling toxic fumes while walking through the garden," the site's coordinators warn on their website.

– What makes a plant toxic?

Toxicity is a plant's defence mechanism against predators (as are thorns), the purpose of which is to avoid being eaten. This is the case of the Mimosa pudica, which closes its leaves on contact while emitting chemicals through the air to throw giraffes off the scent," explains Enrique Salvo Tierra, lecturer in Botany at the University of Malaga.

Their existence is not as rare as it seems. In fact, "97% of the plants on the planet have toxic chemical substances", says the specialist, although not all of them are as harmful to our health as those in the Poison Garden. Even so, we must be careful, because even if we are not going to make a salad out of poppies or ferns, children and pets are likely to put fruit or leaves in their mouths as they look attractive.

Oleander (Nerium oleander)

Oleander (Nerium oleander)

On the central reservations of dual carriageways, in parks, in our own gardens... In Spain the oleander is known for its beauty. It is eye-catching and hardy, but ingesting it can be deadly.

According to the Spanish Inventory of Traditional Knowledge Related to Biodiversity, drawn up by the Ministry of Agriculture and Fisheries, Food and Environment, its therapeutic use is negatively judged due to its potential toxicity. "Between 15 and 20 grammes of fresh oleander leaf can kill a horse, 10 to 20 grammes can kill a cow, and 1 to 5 grammes can kill a sheep," the report states.

Ivy (Hedera)

Ivy (Hedera)

And what happens if we take a nibble of an ivy leaf? Well, you'd better not: "This creeper that we often use to cover walls or fences is known for the toxicity of its fruits, which are full of alkaloids, metabolites contained in many plants that produce physiological effects," says Alberto Altés, lecturer in Botany at the University of Alcalá de Henares (Madrid).

And what are these effects? "It can cause drastic hypotension (drop in blood pressure) or temporary or permanent loss of vision in humans, while in animals its excessive consumption causes diarrhoea and reduced milk production," warns the government document.

Poinsettia (Euphorbia pulcherrima)

Poinsettia (Euphorbia pulcherrima)

No one would think that this typical Christmas ornamental plant could cause a nasty experience for humans and animals. Its toxicity is due to the milky sap that runs through its stems and membranes, which acts as an irritant in contact with the skin and mucous membranes.

Eye discharge, conjunctivitis, redness and sores on the skin, as well as digestive discomfort (if ingested) are its main symptoms, although in principle they are not serious. Something similar occurs with the ficus, another common decorative plant in the home.

Hydrangea

Hydrangea

It was at the whim of the French King Louis XIV, who ordered his henchmen to search for new plant varieties from across the seas to decorate his gardens, that this plant arrived in Spain. It owes its name to a cabin boy on the ship known as Batet. When the king discovered that, in reality, Batet was a woman called Hortensia, he thought it appropriate to give it that name.

It is a lovely story but the effects of ingesting its leaves and flowers are less so. In small doses it causes vomiting, diarrhoea and abdominal pain and, although unlikely due to its bad taste, in large doses it can cause halitosis, asphyxia, arrhythmia and apnoea.

Yew (Taxus baccata)

Yew (Taxus baccata)

It is one of the most toxic plants there is. The whole plant is highly poisonous, except for the red flesh of its fruits. Between 50 and 100 grammes of its leaves are lethal to an adult, according to the ministry's report, and the toxins it releases are absorbed so quickly that death can occur without the body having time to show any symptoms.

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