Plants

Giant hogweed (Heracleum mantegazzianum) is an attractive, invasive plant with sap that can cause severe skin burns.

Do not place giant hogweed into the green garden or blue recycling bin. To dispose please use a specialist contractor.

The tall plant can reach over 3.5m (11.5ft) or more with flower heads as large as 60cm (2ft) across. The cow-parsley like plant can look attractive with thick often purple-blotched bustle stems.

While the plant is not illegal and there is no statutory obligation for home owners to eliminate giant hogweed Central Government introduced legislation to help control the weed.

The problem with Giant hogweed

Giant hogweed is invasive and potentially harmful. Chemicals in the sap can cause photodermatitis or photosensitivity, where the skin becomes very sensitive to sunlight and may suffer blistering, pigmentation and long-lasting scars.

While this is one of the species, there are as many as four other giant hogweeds at large in Britain some of which are biennial and others perennial. However, when tested all of these had high levels of furanocoumarins (the chemicals which cause burning by making the skin sensitive to sunlight) and so all pose a risk to public health. There is also a native hogweed, Heracleum sphondylium, which will be a familiar plant to gardeners and those who like walking in the UK. It can grow to 6 foot or so when in flower and can cause rashes and other skin complaints but reactions tend to not be as severe as with larger species.

Legislation

Giant hogweed has been applied to legislation within the Countryside Act 1981 and lists the plant under Schedule 9, Section 14 meaning it is an offence to cause giant hogweed to grow in the wild of England and Wales. The weeds can be subject to Anti-Social Behaviour Orders where occupiers of giant hogweed infested ground can be required to remove the weed or face penalties.

How to control giant hogweed

When controlling giant hogweed always wear gloves, cover your arms and legs, and ideally wear a face mask when working on or near it (this is so a strimmer will not cut the sap and it hits your face). Cut plant debris, contaminated clothing and tools are potentially hazardous too. Wash any skin that comes in contact with the plant immediately. Ensure any contractors working on your land are aware of the risks.

Non-chemical

• If in a garden pull up plants by hand when the soil is moist. Do this in May when the plant hogweed has reached a reasonable height, but before it has produced its flowering spike.
• Never let hogweed set seed, but allow the flower spike to form and then remove it before the flowers fades.
• Larger scale areas - leave to a specialist contractor

Chemical

• Weedkiller based on glyphosate is usually the best choice as this will also kill roots. Giant hogweed prefers moist fertile area often near waterways. Seek advice from the Environment Agency before undertaking spraying near rivers, streams and ponds.