Giant hogweed

Heracleum mantegazzianum

Giant hogweed

Giant hogweed

Legal Status: Unwanted Organism - BNZ
Status in New Zealand: Established
Organism: Land plants

Other common names

wild rhubarb, cartwheel flower, wild parsnip


Giant hogweed is a perennial that grows 4-6 m in height. It has stout dark-reddish-purple stems, and spotted leaf stalks with sturdy pustulate bristles which contain a toxic sap. The stems and stalks are hollow, the stems being 5-10 cm in diameter. Giant hogweed has extremely large leaves (up to 1.5 m) and tuberous root stalks. When the plant is two to three years old it produces large umbrella-like clusters of greenish-white flowers. It usually grows on the banks of rivers or creeks.


Giant hogweed is poisonous to humans. Touching it, or exposure to dust from weed-eating, can irritate skin and cause blisters and swelling. The toxin actually causes photosensitisation so that the skin reacts badly to sunlight.

What to do

Contact your regional council to determine the status of this species and responsibility for control and/or advice on control.

Page last updated: 22 October 2008