Giant Hogweed (Heracleum mantegazzianum) The photo above shows Giant Hogweed on the right in comparison to our native Common Hogweed (Heracleum sphondylium) on the left. Giant Hogweed facts: Perennial – grows 5-7m. Member of parsley family. Arrived in UK 1893 from Caucasus. Sap causes serious rashes when skin exposed to sunlight. Can cause blindness. Can be controlled by spraying, grazing, cutting or digging- up. Spraying with Glyphosphate (Round Up) is a successful treatment. Spread by rivers and seeds last 3 or more years For more details on Giant Hogweed, please see here.