The poison giant invading Britain: How the sap from hogweed can cause third degree burns and even blindness 

By Becky Dickinson For The Daily Mail

Published: 18:50 EST, 12 July 2015 | Updated: 10:28 EST, 13 July 2015

Nothing could be more pleasant than a walk in the British countryside in summer. Hedgerows scattered with frothy blooms of cow parsley and elderflower, crimson poppies and oxeye daisies nodding in the sun, the scent of wild honeysuckle.

Yet such a simple country stroll could be dangerous — thanks to a plant with sap that can cause third-degree burns and even blindness.

Last week, five children suffered severe burns and one was scarred for life after brushing past giant hogweed growing in two country parks.

Last week, five children suffered severe burns and one was scarred for life after brushing past giant hogweed growing in two country parks

Annie Challinor, seven, was left with a permanent scar after her arm blistered when it touched the plant on a family walk in Clifton Country Park, Salford, Greater Manchester.

And four teenage boys suffered agonising blistering after coming into contact with giant hogweed in Moses Gate Country Park, Bolton.

Three of the children needed hospital treatment and may have to take painkillers for months. One boy is said to have screamed: ‘I want to die, stop this pain.’ And little Annie has been told she will have to use total sunblock on her arm for the rest of her life.

So what is this poisonous menace, and why is it lurking in our countryside at all?

Giant hogweed, Heracleum mantegazzianum, can grow up to 16 ft high. It’s a member of the Apiaceae family, which includes carrots, parsnips and celery. But unlike its tasty cousins, it contains a powerful toxin.

Its stem holds a sap that makes skin extremely sensitive to UV radiation, so it blisters if exposed to sunlight. The effect can last for many years.

Blistered: Conor Knott, 13, was kept in hospital overnight after suffering burns to his hand (pictured)

Giant hogweed was imported here in 1893 by Victorian plant hunters. From the Caucasus mountains and central Asia, it was prized as an ornamental plant and blithely sown by landowners. At the start of the 20th century it escaped into the wild, where it has been taking root ever since.

According to the Botanical Society of the British Isles, it is widespread across England and has invaded large areas of Scotland, Northern Ireland and parts of Wales, typically colonising riverbanks, verges and wasteland.

Reports of it have been rising since 2000, and there has been a recent surge in sightings.

‘If the plant was small and easy to miss, this could just mean a lot more people have been looking for it,’ says biologist Dr Graham Rowe, from the University of Derby. ‘However, given the size of the giant hogweed, this is more likely to be a genuine increase.’

Breaking the stem or leaves, or just brushing against the plant, causes the sap to ooze out. This sap is phototoxic, meaning it stops the skin protecting itself from sunlight.

Chemicals called furocoumarin compounds in the sap lead to painful, blistering burns, and the reaction can be long-lasting, so victims have to keep affected areas out of the sun for years.

Worse still, a tiny amount of sap in the eyes can lead to temporary or even permanent blindness.

Dr Tabi Leslie, of the British Association of Dermatologists, says: ‘The sap is a psoralen, which makes you sensitive to sun and causes intense redness followed by large blisters. Some people develop secondary infections from the blisters.’

No wonder the plant is blacklisted by the Government. Under the Wildlife and Countryside Act 1981, it’s an offence to cause giant hogweed to grow in the wild — this includes moving contaminated soil or plant cuttings.

Anyone caught doing so faces up to two years in prison or a fine of up to £5,000.

But it’s not just ourselves we need to worry about. The plant is putting wildlife at risk, too.

‘It is a threat to some British flora and there will be a knock-on effect for animals, too,’ says Dr Rowe. ‘It can simply push smaller plant species out of the way.’ The flower heads can grow to the size of umbrellas and just one plant can produce 50,000 seeds.

Painful: Reid Daley has been in and out of Royal Bolton Hospital. His stepfather Mathew Cocklin said Reid had been given ibuprofen and pain killers. He said that Reid told him 'I want to die, stop this pain from hurting'

As it frequently grows on the banks of rivers, seeds fall into the water and can be dispersed many miles downstream.

It is tough to eradicate, too. Small plants should be pulled up in May, before the flowering spike is produced.

Large plants are harder to dig up and gardeners are warned to wear gloves and a face mask, and to keep arms and legs covered.

As the sap is activated by sunlight, giant hogweed should only be tackled on dull days.

Clothing and tools that have come into contact with it should be washed carefully.

Serious infestations may require spraying with herbicide, but one treatment is rarely enough.

It can take up to 15 years for the seeds to stop germinating, and even plants cut to the ground will try to flower again. Large infestations should be left to the professionals.

But what if you do touch it accidentally? ‘Affected skin should be washed with soap and water, then covered with clothing or sunblock,’ says Professor Simon Thomas, of the National Poisons Information Service.

As the sap is activated by sunlight, giant hogweed should only be tackled on dull days

Dangerous Hogweed is identified and removed (related)

‘Calamine lotion and analgesics may be helpful, as are tepid baths or cool compresses. Oral antihistamines or steroid creams may be useful for persistent itching.’

Thankfully, giant hogweed is easy to spot. Besides its height, it has a thick, hollow stem that is mottled purple, huge jagged leaves and flower heads. And it is covered in fine bristles like a stinging nettle.

In June and July it produces white flowers held in umbels, or flat-topped clusters, with all the flowers facing upwards. These flower heads can be 2ft across.

Yet Dr Rowe says it’s important to keep things in perspective.

‘Every year a few people die from eating deadly nightshade or yew berries,’ he says. ‘Thankfully, contact with giant hogweed sap tends to be restricted to a limited area of the body — and the plants are easy to spot.’

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