Giant hogweed may look impressive, towering over garden fences with its huge, umbrella-like flowers, but don’t be fooled. This invasive species is one of the most dangerous plants in the UK, capable of causing severe skin burns and long-term sensitivity to sunlight. Whether you’re managing land, tending a garden, or simply walking by a riverbank, knowing how to identify and remove giant hogweed safely is essential.
What is Giant Hogweed?
Giant hogweed (Heracleum mantegazzianum) is a non-native, invasive plant originally introduced from the Caucasus as an ornamental curiosity. It can grow up to 5 metres tall and produces large white flower heads in summer.
It’s now widely found along riverbanks, roadsides, and unmanaged spaces, and it spreads aggressively through its seeds. Worse still, it poses a serious risk to health.
🔥 Important: The sap of giant hogweed contains furanocoumarins. When it comes into contact with skin and is exposed to sunlight, it can cause serious burns, blisters, and scarring; a condition called phytophotodermatitis.
How to Identify Giant Hogweed
Recognising giant hogweed early is key to safe management. Here’s what to look for:
- Height: Up to 3–5 metres tall
- Leaves: Huge, jagged, deeply lobed, can be over 1 metre wide
- Stems: Thick, green with purple blotches and stiff white bristles
- Flowers: Large white umbels (umbrella-like clusters), up to 80cm across
- Seeds: Flat, brown, and oval-shaped. Spread by wind and water
Compare it to native cow parsley or hogweed, which are much smaller and less aggressive.
Why It’s a Problem
- Health hazard: The sap can cause burns and long-term skin sensitivity
- Environmental impact: It outcompetes native species and spreads rapidly
- Legal responsibility: Under the Wildlife and Countryside Act 1981, it’s an offence to plant or allow giant hogweed to spread in the wild
How to Get Rid of Giant Hogweed Safely
🚨 Never strim, mow, or brush-cut giant hogweed. This can spray sap and increase exposure risk.
Removal methods:
- Manual control (with extreme caution):
- Wear full protective clothing: waterproof gloves, long sleeves, trousers, face protection.
- Dig out plants before they set seed (ideally in early spring).
- Sever the root at least 15cm below the soil surface.
- Chemical control:
- Use a glyphosate-based herbicide applied directly to the leaves in spring or early summer.
- Repeat applications are often necessary.
- Avoid drift onto non-target plants.
- Professional removal:
- For large infestations or high-risk areas (e.g. near schools or footpaths), consider licensed contractors.
🌱 Note: While manual and cultural methods are always the preferred route, when invasive plants pose a threat to biodiversity and gardeners are struggling to control them effectively, the targeted use of regulated weedkillers may be an option.
Garden centres and large retailers that sell weedkillers usually have trained staff who can help recommend a suitable product for your specific situation. Always read and follow the label instructions carefully.
Disposal:
- NEVER compost. Cuttings and roots are classified as controlled waste.
- Follow local council advice for safe disposal or licensed removal.
How to Prevent the Spread
- Do not buy or grow giant hogweed seeds; it’s illegal to plant it intentionally.
- Clean tools and boots after working near infested areas.
- Remove young plants before they flower or set seed.
- Report large infestations to your local council or environmental body.
Common Questions
Typically June to July, with seeds forming soon after.
You may not feel anything immediately, but when the sap reacts with sunlight, it can cause burning, blistering, and long-term skin sensitivity.
Yes, it can harm animals in a similar way, especially if ingested or if sap contacts skin.
Each plant can produce up to 50,000 seeds, which are spread by wind and water, especially along rivers.
Further Reading
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