Weed Department
Idaho State Noxious 
Weed Law
Giant Hogweed


Giant hogweed is a perennial distinguished by its large size, capable of growing to a height of 15-20 feet. It has stout dark reddish-purple spotted stems and leaf stalks. Stalks and stem produce sturdy pustulate bristles.

Flower Description: Giant hogweed has broad, flat-topped flower clusters (umbels) of many small white flowers. Each flower cluster may grow to a diameter of 2.5 feet.

Leaf Description: The compound leaves of giant hogweed may expand to five feet in breadth. Each leaflet is deeply cut.

Stem Description: The stem and stalks are hollow and vary 2 to 4 inches in diameter.

Fruit/Seed Description: The flowers produce large elliptic dry fruits marked with brown swollen resin canals.


Interesting Facts:

It forms dense canopies outcompeting native species and increasing soil erosion. It exudes a clear watery sap which sensitizes the skin to ultraviolet radiation, resulting in severe burns to the affected area causing blistering and painful dermatitis.