September 21, 2023

The dangerous plants lurking in plain sight

Hemlock on an overgrown path in Bucklesham, Suffolk.

Hemlock, which can be fatal if swallowed, was found along a path near a village school

On Monday, it emerged that children’s lives were “at stake” in a Suffolk village after hemlock – a plant that can be fatal if ingested – was found on their normal walk to school. However, Hemlock is far from our only green neighbor posing a risk.

The days of the Bucklesham hemlock are numbered.

First reported to Suffolk County Council in June by Parish Council Chairman David Brinkley, the authority has pledged to close the road and remove the offending plant.

In his call to action, Mr Brinkley says delays in removing the plant “put children’s lives at risk”.

The umbrellas of the hemlock plant

The alkaloids in Hemlock cause violent vomiting and nervous system paralysis, with death usually due to respiratory failure

Headmaster Rachael Rudge has similar concerns.

“To walk on the roads because the path is not safe because of all the hemlock and vegetation puts them in this very difficult and unsafe position,” she says.

But according to Prof Iain Barr, from the University of East Anglia, after the removal of the hemlock, another 28,000 remain in the UK.

Prof Barr, a professor of field ecology, tells the BBC about some other dangerous plants in plain sight and why some pose such a threat.

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Giant hogweed

giant hogweed

The poisonous juice of giant hogweed, which grows near canals and rivers, can cause burns, blisters
and scars to those who come into contact with it

The giant hogweed – Heracleum mantegazzianum — is not to be messed with, says Prof. Barr.

It is one of over 100 poisonous plants found in the UK and listed as potentially harmful by the Royal Horticultural Society.

“If you touch it and your body reacts to it, it can trigger a reaction and make you very susceptible to sunburn,” says Prof. Barr. “You don’t want to come into contact with any part of it.”

The poisonous sap of the plant, which grows near canals and rivers, can cause burns, blisters and scars to those who touch it.

The plant, a close relative of cow parsley, has white flowers, thick bushy stems and can grow over 5 meters in height.

Native to Central Asia, it was introduced to Britain in 1893 as an ornamental plant, but “escaped domestication”.

Toxic components in the leaves, stems, roots, flowers and seeds can be transferred to the skin through contact.

It is often confused with its native relative, the hogweed.

“That’s toxic too,” says Prof. Barr. “But less.”

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“People should just step back and admire the foxglove,” says Prof. Barr

A staple favorite for a shadier spot in the garden, the beloved foxglove floral beauty has a darker side.

Foxglove – digitalis – is a source of digitoxin, a glycoside in the drug digitalis, which has been used since 1785 as a heart stimulant.

It is also known for its toxicity in all parts of the plant.

Consuming the leaves can cause oral and abdominal pain, nausea, vomiting and diarrhea.

In severe cases, symptoms can include visual disturbances, plus heart and kidney problems.

“People just have to step back and admire it,” says Prof. Barr.

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Deadly nightshade

Belladonna, or deadly nightshade

Deadly nightshade is one of the UK’s most poisonous plants and just a few berries would be enough to kill a person

“Don’t eat it,” says Prof. Barr.

Deadly nightshade is one of the UK’s most poisonous plants and just a few berries, which contain tropane alkaloids, are said to be enough to kill a person.

“It’s part of the tomato family,” says Prof. Barr. “It can be found in forests, although it’s not as common as it used to be.”

The Solanaceae family is huge with over 2,500 members, including tomatoes, potatoes, peppers, eggplants, bell peppers, tobacco, deadly nightshade, and henbane.

Despite its deadly potential, the nerve gas antidote atropine sulfate can be extracted.

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Hemlock water Rodent

Hemlock water Rodent

Hemlock waterdrop herb is toxic to humans and animals if swallowed

“The hemlock water rodent is very, very common around the [Norfolk and Suffolk] Broads,” says Prof. Barr. “It’s also very poisonous.”

Also known as the “poison parsnip”, hemlock water Rodent – Oenanthe crocata – is one of the most poisonous plants native to the United Kingdom.

Both hemlock and hemlock waterdropweed are part of the carrot family, but live in different habitats and have different toxins.

The tubers, stems and leaves all contain a toxic and potent antispasmodic agent called oenanthotoxin, which targets the central nervous system.

Hemlock, on the other hand, contains five alkaloids – coniine, conhydrin, pseudoconhydrin, methylconiine and ethylpiperidine – which cause violent vomiting and paralysis of the nervous system.

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‘Chemistry and Evolution’

prof.  Ian Barr

Plant toxins evolved as a protective mechanism, says Prof. Barr

Deaths from poisonous plants are very rare in the UK, but they do happen. The Office for National Statistics found that six people died from the “toxic effect of ingested plants” in 2016.

But how do plants become so poisonous that they can kill humans?

“It all has to do with chemistry and evolution,” says Dr. Barr. “Plants have developed toxins to prevent them from being eaten.

“So a plant that is slightly more toxic to a grazing animal than the one next to it has a small advantage.

“Over time, this process leads to a point where certain plants can become highly toxic to certain species.”

The majority of the UK’s native poisonous plants evolved their toxins to scare off huge creatures like woolly mammoths or 2-metre-long aurochs, rather than us humans, he said.

“If an aurochs or mammoth were overgrazed, the plant’s alkaloids wouldn’t make it feel as good,” he says.

“It’s not designed to kill them, just make them unwell and stop them eating.”

Plant poisons were certainly not developed, he says, to prevent children from walking to school.

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