Giant Hogweed (Heracleum mantegazzianum) was introduced as an ornamental garden plant in the 19th century. However due to its successful invasive nature it has taken hold in areas where it quickly forms dense stands. It commonly grows along river banks, enjoying the damp areas and can often be found growing along roadside verges/waste-grounds.
A fine looking plant with large heads of small creamy white flowers (similar to our native hogweed) that appears from June – September. Its leaves are also stunning and it is understandable why the gardeners of yesteryear planted out this herbaceous plant. Its exotic leaves, that are sharply toothed, almost angry looking, can quickly grow up to 1-1.5 metre wide. Many seeds are produced but only after a number of years (commonly 3-5) when the plant has built up sufficient resources to flower and set seed.
However, as beautiful as it is, this plant comes with a serious health warning. Fine hairs/bristles on the stems, visible to the naked eye mark the glands that produce phototoxic sap that if allowed to get on human skin can result in serious burns and blisters after the skin is exposed to the sunlight. According to the Department of Agriculture it may cause livestock problems if eaten.
Giant Hogweed, also impacts on our local biodiversity by shading out our native river bank vegetation reducing plant diversity, leading to riverbank erosion and ultimately impacting on water quality.
After flowering, the plant dies completely. As a minimum we need to prevent flowering. However, due to its serious health warning, great care is needed and expert advice is needed for its successful and safe removal. We are asking members of the community to send us sightings to firstname.lastname@example.org
Sightings should also be recorded on the National Biodiversity Data Centre App