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Giant hogweed: the facts

You may have heard about the dangers of giant hogweed – a non-native invasive plant which can cause burns. So we’ve put together the facts for you, from identification to staying safe.

What is giant hogweed?

Giant hogweed (Heracleum mantegazzianum) is a plant in the Apiaceae family (previously known as the Umbelliferae). This family includes some well-known plants such as parsley, carrot, parsnip, cumin and coriander.

The flowers of giant hogweed are clustered on large, umbrella-shaped flower heads.

Credit: Appaloosa / Wikimedia Commons

Where does giant hogweed grow?

Giant hogweed is not native to the UK. It originates from the Caucasus Mountains and Central Asia. It was first introduced to the UK as an ornamental in the 19th century where it escaped and naturalised in the wild. It can now be found throughout much of the UK, especially colonising river banks where its seeds are transported by the water.

What does giant hogweed look like?

Giant hogweed looks like an enormous cow parsley. When it’s fully grown, it can reach towering heights of between 1.5m to 5m and have a spread of between 1 and 2m. It forms a rosette of jagged, lobed leaves in the first year before sending up a flower spike in the second year and then setting seed.

Stems: green with purple blotches and stiff, white hairs. Stems are hollow with ridges and have a thick circle of hairs at base of each leaf stalk.

Leaves: huge, up to 1.5m wide and 3m long and is deeply divided into smaller leaflets. It looks a bit like a rhubarb leaf, with irregular and very sharp or jagged edges – which has given rise to one of its other common names – wild rhubarb.The underside of the leaf is hairy.

Flowers: appear in June and July. They are small and white (or slightly pink) and are clustered on umbrella-like heads known as umbels that can reach a diameter of 60cm. All the flowers on the umbel face upwards.

Seeds: dry, flattened, and oval. Almost 1cm long with tan with brown lines extending 3/4 of the seed length.

How dangerous is giant hogweed. What happens if you touch it? How to tell if it is giant hogweed? We've put together the facts for you. ]]>