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Heracleum mantegazzianum
Also called Mantegazzi's Cow-Parsnip, Cartwheel Flower, Giant Cow Parsnip, Hogweed
Giant hogweed is a very large, monocarpic perennial in the carrot family that flowers once and then dies, usually reaching 2 to 5 m tall. It is best known as a dangerous invasive weed, since its sap causes severe skin burns in sunlight, so it should not be grown or handled bare-skinned.
Heracleum mantegazzianum, commonly known as giant hogweed, is a monocarpic perennial herbaceous plant in the carrot family Apiaceae. H. mantegazzianum is also known as cartwheel-flower, giant cow parsley, giant cow parsnip, or hogsbane. In New Zealand, it is also sometimes called wild parsnip (not to be confused with Pastinaca sativa) or wild rhubarb.
Giant hogweed is native to the western Caucasus region of Eurasia. Introduced to Britain as an ornamental plant in the 19th century, it has also spread to other areas of Western Europe, as well as the United States, and Canada. Its close relatives, Sosnowsky's hogweed and Persian hogweed, have similarly spread to other parts of Europe.
The sap of the giant hogweed plant is phototoxic. The sap contains furanocoumarins, which leads to phytophotodermatitis, a serious skin inflammation. A phototoxic reaction can begin as soon as 15 minutes after contact with the sap. Photosensitivity peaks between 30 minutes and two hours after contact but can last for several days. Authorities advise that all humans (especially children) should stay away from giant hogweed. Protective clothing, including eye protection, should be worn when handling the plant. Parts of the body that come into contact with the sap of giant hogweed should be immediately washed with soap and cold water, and further exposure to sunlight should be avoided for at least 48 hours. Other Heracleum species such as H. maximum, are likewise phototoxic, and hence similar caution is advised. Owing to physical similarities to other hogweeds in the genus Heracleum, giant hogweed and its close relatives are sometimes mistaken for harmless plants.
Giant hogweed is widespread throughout western and northern Europe, especially along terrains such as coastal areas and riverbanks. By forming dense stands, it can displace native plants and reduce wildlife habitats. It has spread in the northeastern and northwestern United States and southern Canada, and is an invasive species across western Europe; in sites where it has settled, it overtakes the local native species, H. sphondylium.
Persian Hogweed · Sosnowsky's Hogweed · Hogweed · Cowparsnip
Text excerpted from the Wikipedia article Heracleum mantegazzianum by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.
