Giant Hogweed: where does poisonous plant grow in UK, how to treat burns, and is it the same as cow parsley?

The dangerous plant is known to thrive in warm weather in the UK

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As the weather takes a turn for the better across the UK following an unusually wet May, many of us will be spending more time outdoors in a bid to catch some sunshine.

Whilst you’re out and about, whether by yourself, with friends or family, or walking your dog, you should be on the lookout for a plant called Giant Hogweed, as it could spell danger for those who come into contact with it.

This is everything you need to know.

What is Giant Hogweed - and is it dangerous?

Giant hogweed is dangerous and can cause burns - Credit: AdobeGiant hogweed is dangerous and can cause burns - Credit: Adobe
Giant hogweed is dangerous and can cause burns - Credit: Adobe

Giant Hogweed, also known by its Latin name Heracleum Mantegazzianum, originated in Southern Russia and Georgia.

The plant is part of something called the Apiaceae family, which includes well known vegetables and herbs such as parsley, carrot, parsnip and coriander.

Giant Hogweed was first introduced to Britain and Europe in the 19th century, from the Caucasus Mountains. The earliest documented reference to the plant has been traced back to the Royal Botanic Gardens Kew Seed List of 1817, where seeds of the plant were listed.

The plant itself can reach over 10ft in height and, according to The Royal Horticultural Society (RHS), “most gardeners will want to eradicate it, as it is potentially invasive and the sap can cause severe skin burns”.

The reason the plant is dangerous is because of its sap.

The sap contains a chemical called furocoumarin which makes the skin sensitive to the sun, and can cause bad blistering.

The blistering can even recur over the span of months, and even years.

What does Giant Hogweed look like?

The Woodland Trust outlines the appearance of Giant Hogweed so that you can better identify the dangerous plant:

- Stems: the stems are green with purple blotches and stiff, white hairs. The stems are hollow with ridges and a thick circle of hair at the base of each leaf stalk

- Leaves: the leaves are huge, and can measure up to 1.5m wide and 3m long, and are often divided into smaller leaflets. The Woodland Trust compares them to rhubarb leaves, with irregular and jagged edges, with the underside of the leaf being described as hairy

- Flowers: the flowers of the Giant Hogweed appear in June and July, and are small and white and appear in clusters on “umbrella-like heads” that face upwards

Seeds: the seeds are dry, flattened and an oval shape, almost 1cm long and tan in colour with brown lines

You can tell the difference between Giant Hogweed and regular hogweed by looking at the leaves - regular hogweed leaves are going to be more rounded versus the jagged edges of Giant Hogweed leaves.

Additionally, it can be easy to confuse Giant Hogweed and its lookalike cow parsley.

You can tell the difference between the two due to some distinct features - cow parsley can only grow about three to four feet tall, unlike Giant Hogweed, which can reach staggering heights of almost 12 feet.

Cow parsley also has smaller florets and broader leaves that are, again, much more rounded than the jagged leaves of Giant Hogweed.

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Where is Giant Hogweed found?

The plant is found throughout the UK, but more specifically, it’ll be growing by river banks where the seeds are transported via the water.

The RHS also says that areas affected by Giant Hogweed include “gardens and allotments adjacent to infected woodland, healthland or common land”.

You can view the distribution of Giant Hogweed reports across the UK on the What Shed website.

You can zoom into specific regions of the UK to see how many reports of Giant Hogweed have been made in certain areas.

How do I get rid of Giant Hogweed?

If you find your garden or allotment being invaded by Giant Hogweed, you’re going to want to get it removed.

While there is no statutory obligation for landowners to get rid of Giant Hogweed, you should be aware that it is illegal to plant or grow certain invasive and non-native plants in the UK, and this includes Giant Hogweed.

The UK government website states: “You must not import, transport, keep, breed, sell, use or exchange, grow or cultivate, or release into the environment certain invasive alien species.

“If you do, you can be fined or sent to prison for up to two years.”

The website goes on to explain that soil or plant material contaminated with invasive non-native plants can cause ecological damage, and could be classified as controlled waste - Giant Hogweed is classified as controlled waste.

To dispose of Giant Hogweed, the government website states that you must:

- Use a registered waste carrier

- Send it to an authorised or suitable disposal site - you can check with the site directly, contact your local authority or check the Environmental Agency public register

Your local authority can help arrange the disposal of Giant Hogweed. You can check who your local authority is by using the Government website.

You cannot compost most non-native plants because they will usually survive the composting process and can infect areas where compost is used.

When dealing with Giant Hogweed, the RHS says: “Always wear gloves, cover your arms and legs, and ideally wear a face mask when working on or near it.

“Cut plant debris, contaminated clothing and tools are potentially hazardous too.”

How do I treat Giant Hogweed burns?

If you accidentally get Giant Hogweed sap on your skin, Healthline says that you should wash the area with mild soap and cool water as quickly as possible. You should keep the skin covered when you’re outside to protect it from the sunlight.

If a rash or blister begins to form, you should seek medical attention. Your treatment will depend on how severe your reaction is.

“Skin irritation that’s caught early might be treated with a steroid cream and nonsteroidal anti-inflammatory drugs, such as ibuprofen, to relieve pain,” Healthline explains. “Severe burns could require surgery to graft new skin over the damaged skin.”

Healthline also explains that the Giant Hogweed sap can damage more than just your skin - if the sap gets in your eyes, you can experience either temporary or permanent blindness.

Additionally, breathing in sap particles can result in respiratory problems.