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Pesticide Safety Education Program

Ohio State University Extension


Giant Hogweed (Heracleum mantegazzianum)

Description: A herb in the carrot family (Apiaceae), growing 15 to 20 feet in height.

Life cycle: Biennial

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

Flower: Small white floret

Fruit: Large elliptic dry fruit

Leaf: Leaflets may expand to five feet in breadth.

Stem: Hollow stalks and stems

Root: Tap root

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