What is giant hogweed, the UK’s ‘most dangerous’ plant?

Non-native, invasive species is on the rise and can hospitalise those who touch it

Andy Gregory
Tuesday 12 May 2020 14:35
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Brush with toxic hogweed plant burns Virginia teen's face

Experts have warned that a pernicious species once dubbed the UK’s “most dangerous” plant has been spreading across the country for years.

So what makes giant hogweed so hazardous, how can it be recognised, and how can it be safely disposed of?

What is it?

Originally found in the Caucuses, the carrot family member known as Heracleum giganteum is thought to have been first introduced to Britain in 1817, when seeds were sent from Russia to Kew Gardens.

While initially favoured in ornamental gardens due to its pleasant appearance and impressive stature – reaching heights of more than five metres (16 feet) – it became illegal to grow the plant in gardens under the Wildlife and Countryside Act 1981, as a result of it being highly toxic.

Despite its innocuous appearance, its sap can cause highly painful burns, which blister within 48 hours, often hospitalising people and leaving them with permanent scars.

The injuries result in the skin becoming very sensitive to sunlight, which can lead to further blisters, scarring or sun damage years down the line. The sap can also lead to blindness if it gets in the eyes.

How is it recognised?

While giant hogweed typically grows near canals and rivers, experts warn it has spread to gardens, parks and verges in recent years.

Plant Tracker – an Environment Agency-based database of invasive, non-native plants – reports hundreds of sightings across all four UK nations, as far afield as Inverness, Pembrokeshire, County Londonderry and Kent.

It is often mistaken for cow parsley or hemlock due to its long stems and flat-topped clusters of white leaves.

While, like hemlock, its thick, bristly stems can also be pocked with purple blotches, it has less ferns and can grow significantly taller than either plant, with flower heads spanning up to two feet wide.

How can it be disposed of?

Although there is technically no statutory obligation for landowners to rid their properties of the weed, many property owners and local authorities choose to do so due to the dangers posed to the public.

It is, however, an offence to allow the weed to spread into the wild – so it is possible that landowners could be deemed responsible for outbreaks believed to stem from plants on their property.

Furthermore, landowners who fail to clear it from their land have in the past been handed anti-social behaviour orders.

Ideally, always wear gloves, face masks and ensure all skin is covered while dealing with giant hogweed, bearing in mind that anything coming into contact with it – be that clothing, tools or skin – will be contaminated and should be washed immediately.

Young plants can be pulled up using gloved hands when soil is wet, around May when it has reached a reasonable heigh but before it has produced its flowering spike, according to the Royal Horticultural Society.

For larger plants it might be necessary to loosen the roots with a fork first. Larger scale areas should probably be left to professionals to dispose of.

“There is no need to be scared of the plant – just use common sense – and take action if you identify it on your property,” a Mersey Rivers Trust spokesperson told The Independent, adding: “Keep children away from the plant until it has died off fully.

“The plant can produce up to 100,000 seeds, and the seed bank can last up to 15 years – meaning a prolonged period of vigilance for newly emerged seedlings and a prolonged period of treatment.”

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