Giant Hogweed FAQs

What is Giant hogweed?

Giant hogweed (Heracleum mantegazzianum) commonly known as cartwheel-flower, wild parsnip, wild rhubarb, or giant cow parsnip is a non-native invasive perennial plant often found growing near watercourses, motorways and waste ground across the UK. Native to the Caucasus Region and Central Asia, Giant hogweed was introduced to Britain as an ornamental plant during the 19th century and has since thrived due to its natural resistance to frost and huge number of seeds produced.

What does Giant hogweed look like?

New Giant hogweed growth appears as dark green spiked leaves in March/April developing large hollow ribbed stems green in colour with spots of purple. Tiny, coarse hairs cover the stem and base of the leaves. Mature Giant hogweed produces large white flower heads which can contain up to 50,000 broad, flattened seeds. Once fully developed, Giant hogweed can stand 5m tall with enormous jagged leaves spanning 1m, shielding the surrounding vegetation from sunlight and preventing their growth.

Why is Giant hogweed a problem?

Giant hogweed is a phototoxic plant, secreting a toxic sap from the stem and leaves posing a serious health risk to humans and animals. If the sap comes into contact with bare skin and is then exposed to a source of ultraviolet radiation such as sunlight, it can cause severe burns and blistering. Due to the unusual appearance of the plant it can often be disturbed by passersby, particularly children, who are most at risk from exposure to the sap. As a result, the presence of Giant hogweed on or around footpaths and roads can restrict public access. Growth can affect the surrounding environment as it rapidly colonises large areas with dense clusters, their enormous leaves starving local plant life of sunlight.

What damage can Giant hogweed cause?

Giant hogweed can cause serious skin irritation and burns often becoming apparent 15-20 hours after direct contact with the plants phototoxic sap. Burns to the skin sustained from exposure to the sap can result in scarring and recurring skin sensitivity to ultraviolet light. Contact directly to the eyes can cause temporary blindness, in some cases resulting in permanent damage. Giant hogweed can be found growing near rivers and streams where seeds can be easily dispersed causing erosion to river banks as they develop and die back in the winter. The production of so many seeds annually can help Giant hogweed to rapidly colonise areas, denying native species the chance to grow unhindered and reducing biodiversity in the local environment. This can have devastating effects to the surrounding wildlife, tampering with the delicate balance of the ecosystem and potentially causing irreversible damage.

How can you kill Giant Hogweed?


It is possible to control and ultimately eradicate Giant hogweed using a number of methods, some more appropriate than others when factors such as timescale and the surrounding environment are taken into account. The main treatment options are chemical treatment, cutting or burning.

How can I prevent Giant Hogweed spreading?

Giant hogweed spreads its seeds by wind and water dispersal and is therefore difficult to prevent from reproducing. Thousands of loosely attached, low density seeds adorning the flower heads can easily be carried far and wide by light gusts, downstream from infestations on riverbanks and direct contact from humans and/or animals. The most direct means to prevent this from happening is to cut any new growth as and when it occurs, specifically targeting the flower heads of mature plants to prevent seed dispersal. Unfortunately this will not target the roots and dormant seeds underground which can be addressed through application of herbicides. Cattle, pigs, sheep and goats can all graze on Giant Hogweed with no apparent ill effects, suppressing new growth but unlikely to fully eradicate well established infestations.

Can I plant Giant Hogweed?

Under the Wildlife and Countryside Act 1981 it is an offence to introduce Giant hogweed into the wild, although there is no law stating you cannot cultivate it on your property we would highly advise against it!