Giant hogweed poses a significant threat to native flora and fauna, and can also cause serious burns to human skin.
This terrestrial plant can grow up to five metres tall
Giant hogweed facts
Scientific name:Heracleum mantegazzianum
Family:Umbellifer
Native to: Central Asia
Type: Typically biennial, but can be perennial
Predators/herbivores: None
Location: On land, usually near larger canal banks, but can be found near any stretch of water. Widespread across the UK
Giant hogweed in Britain
In 1820, giant hogweed was intentionally planted in gardens close to rivers and ponds due to its striking visual presence. Eight years later, it was first recorded in the wild in Cambridgeshire.
Why is giant hogweed a problem for canals and native wildlife?
Reaching over five metres tall when fully grown, giant hogweed keeps other plants in the shade and prevents the sunlight from reaching them. This increases the risk of bank erosion when the weed dies off in the winter, exposing bare areas where other plants would normally grow.
It also reduces suitable habitat space for a variety of wildlife, including the endangered water vole.
Controlling its spread is challenging. Giant hogweed depends entirely on seed dispersal to spread, and can self-fertilise. Its flowers can hold as many as 50,000 seeds, which are paper thin and about the size of a penny.
The majority fall within four meters of a parent plant and create densely populated areas, but a large proportion also float down waterways, enabling it to grow elsewhere.
Giant hogweed, copyright GBNNSS
Is giant hogweed dangerous to humans?
Giant hogweed is harmful to humans. Coming into contact with any part of this plant (even loosely brushing past it) can burn skin and cause lifelong issues when exposed to sun. This means it is considered to be a serious and significant danger to public health.
You should not attempt to remove giant hogweed from anywhere yourself. It should only be treated by qualified, suitably protected contractors.
If you accidentally come into contact with giant hogweed, you should seek medical advice as soon as possible.
Whilst growing, giant hogweed is similar to cow parsley and our native common hogweed, but at full height it is much larger and easily distinguishable.
It has sharply serrated leaves, which can grow up to three metres long and have bristles on the underside. The plant stems can grow up to five meters tall and 10cm wide, and are also usually covered with sharp bristles.
The flowers, which can stretch to 80cm wide, are white and umbrella shaped.
Giant hogweed
How to report invasive species
If you see an invasive, non-native plant species on one of our canals or rivers, please contact us online or call us on 0303 040 4040 and we'll check if it is already included in our treatment schedule.