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Pesticide Safety Education Program

Ohio State University Extension


Giant Hogweed (Heracleum mantegazzianum)

Giant Hogweed (Heracleum mantegazzianum)

Description: A herb in the carrot family (Apiaceae), growing 15'-20' in height in large clusters. Sap may cause servere skin irritation.

Life cycle: Biennial

Habitat: Along railroads, roadsides, rights-of-ways, vacant lots, streams, rivers, uncultivated or waste lands and agriculture areas.

Leaf: Leaflets may expand to three feet in breadth.

Stem: Hollow stalks and stems light green with purple blotches throughout. 

Flower: Large white inflorescences that can grow up to 2.2' in diameter.

Fruit: Large elliptic dry fruit, seeds orange and 0.5" in length

Root: Extensive taproot.

The problem is….an aggressive competitor. It outcompetes native plant species because of its size, rapid growth and heavy seed production. It contains a substance within its sap that makes the skin sensitive to ultra violet light which is a public health hazard. Large watery blisters usually appear 15 to 20 hours after contact with the sap and sunlight.

mature giant hogweed

giant hogweed leaves

giant hogweed stem

giant hogweed seed head