Giant Hogweed (Heracleum mantegazzianum)

Is the next best known invasive plant in the UK after Japanese Knotweed. It was also introduced by the Victorian’s as another spectacular horticultural specimen and had spread to the countryside in the 1900’s. Since then it has spread the length and breadth of the country, where it frequently colonises riverbanks.

Giant Hogweed is a perennial plant that can take four years before flowering. It can grow up to five metres tall producing a white umbrella-like flower half a metre in size and with leaves up to one metre across.

Each plant can produce 50,000 seeds, which can remain dormant for up to 15 years. Seeds are dispersed by wind and can be carried long distances by water or by human intervention, by means of soil on footwear or on vehicle tyres.

How to identify Giant Hogweed

Japanese Knotweed

Giant Hogweed

Common Ragwort

Himalayan Balsam

Buddleia

Aqautic Invasive Weeds

rosette

flowering

leaves

Why is it a problem

Giant Hogweed presents a public health threat. The stems and underside of the leaves are covered with small hairs coated with poisonous sap and the slightest touch can cause painful blisters and severe skin irritation. Symptoms may take a couple of days to develop, where the skin produces large watery blisters and the effects can be long lasting, resulting in recurrent dermatitis.

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