Invasive plants and tree disease
Giant hogweed: identify it safely and get rid of it
Giant hogweed is a very tall invasive plant with thick blotchy stems, huge jagged leaves and large white umbrella-shaped flower heads. Its sap can cause severe, blistering skin burns that recur in sunlight. Never strim or cut it without protection. Identify it safely, keep clear, and use a specialist for removal.
- Also known as
- Heracleum mantegazzianum
- Easily confused with
- common hogweed (much smaller), cow parsley, hemlock, angelica
- How serious
- High: a genuine skin-burn hazard and a listed invasive plant
- Typical cost
- Specialist treatment varies with the size of the stand; expect a survey fee plus per-season treatment costs
How to identify giant hogweed
Giant hogweed is enormous, often 2 to 5 metres tall. The stems are thick, green with purple blotches and stiff white hairs. The leaves are large, deeply divided and jagged, and can be up to around 1.5 metres across.
The flower heads are large white umbrella-shaped clusters (umbels), similar in shape to cow parsley but far bigger, appearing in summer. The sheer size and the blotchy bristly stem separate it from the much smaller common hogweed and cow parsley. The RHS and Woodland Trust provide identification guidance.
How serious is it?
High: a genuine skin-burn hazard and a listed invasive plant
The main danger is the sap. The RHS warns that giant hogweed sap can cause severe skin burns and blistering, and makes skin sensitive to sunlight so that burns can recur for a long time after contact. Sap in the eyes can cause serious irritation.
It is also a listed invasive plant. gov.uk includes it among invasive non-native plants you must not allow to spread into the wild, and it spreads readily by seed along watercourses and verges, forming dense stands that crowd out native plants.
How to fix it yourself
- Do not strim, mow or cut giant hogweed, as this sprays sap and is a common cause of burns. Keep children and pets away.
- If you must work near it, cover all skin with waterproof clothing, gloves and eye protection, and wash any contact area immediately, then keep it out of sunlight and seek medical advice if sap touches skin or eyes.
- For small plants, carefully digging out the root before flowering, in full protective clothing, can work, but most people use a specialist.
- Glyphosate-based treatment over the growing season can control it, applied with full protection and following the label.
- Treat plant material as controlled waste and follow gov.uk disposal guidance; do not compost it.
When to call a professional
- Any large stand, plants near paths, schools or where people pass, or any situation where safe handling cannot be guaranteed.
- Spread along a watercourse or boundary, where coordinated treatment is needed.
Who to call
- A Property Care Association (PCA) Invasive Weed Control Group member or a specialist invasive-weed contractor.
- Your local council, especially where giant hogweed is on or beside public land or a right of way.
Indicative cost: Specialist treatment varies with the size of the stand; expect a survey fee plus per-season treatment costs. Prices vary by area, severity and access, so always get a written quote.
Frequently asked questions
What happens if you touch giant hogweed?
The RHS warns the sap can cause severe skin burns and blistering and makes skin highly sensitive to sunlight, so burns can recur for a long time. Wash the area immediately, keep it out of sunlight, and seek medical advice, especially if sap reaches the eyes.
How do I tell giant hogweed from cow parsley?
Giant hogweed is far bigger, often 2 to 5 metres tall, with thick purple-blotched bristly stems and huge jagged leaves up to around 1.5 metres across. Cow parsley and common hogweed are much smaller with slimmer, unblotched stems. The size and blotchy stem are the giveaways.
Is giant hogweed illegal in the UK?
Having it is not in itself an offence, but gov.uk lists it among invasive non-native plants you must not allow to spread into the wild, and the plant waste is controlled. It is best identified and managed carefully, with specialist help for larger stands.
Can I get rid of giant hogweed myself?
Small plants can sometimes be dug out or treated with glyphosate, but only in full protective clothing because of the burn risk. For larger stands, plants near where people pass, or any spread along a watercourse, a specialist invasive-weed contractor is much safer.
Sources
Editor, HomesAndHedge
Oliver leads HomesAndHedge's editorial coverage of home and garden problems. He researches and writes the plain-English explainers on pests, invasive plants, damp and mould, drainage and wildlife, drawing on guidance from bodies such as the Property Care Association, the RHS and the NHS, and is clear about when a job needs a qualified professional.
Last reviewed: 8 June 2026