Scientific name: Heracleum mantegazzianum

What Is It?

Giant hogweed is a very large plant that can grow in a variety of environments. It spreads by seed and can be transported easily to backyards, ravines, parks, steams, and roadsides. It crowds out other plants and takes over natural areas, especially moist environments such as riverbanks. It is shade-tolerant, but also thrives in full sun. Giant hogweed was introduced from Asia as an ornamental.

Is It Here Yet?

Yes. Giant hogweed has been documented in numerous locations in Washington.

Why Should I Care?

Giant hogweed forms dense patches that out-compete native species and expose soil, making it more vulnerable to erosion. Giant hogweed’s sap can make skin vulnerable to severe sunburn and blistering.

How Can We Stop It?

Giant hogweed is on Washington’s Terrestrial Noxious Weed Seed and Plant Quarantine list, meaning it is prohibited to transport, buy, sell, offer for sale, or distribute giant hogweed plants, plant parts, or seeds. Giant hogweed is listed as a Class A Noxious Weed in Washington, meaning its eradication is required; however given giant hogweed’s harmful effects to people, seek assistance from your county noxious weed control board before attempting any eradication efforts. Importation and interstate transport of giant hogweed further is regulated by the U.S. Department of Agriculture under the Federal Noxious Weed list (7 CFR 360).

What Are Its Characteristics?

  • Grows more than 15 feet tall.
  • Large, wide leaves can be up to 3 feet long.
  • Many small, white flowers cluster together in a group that can be 2 feet long or longer.
  • Large, purple, hollow stems.

How Do I Distinguish It From Native Species?

Giant hogweed may be distinguished from native cow parsnip in that it is much larger. Cow parsnip rarely exceeds 6 feet in height. It also has smaller flower clusters, and the hairs on the underside of the leaf are soft, wavy, and shiny. Please note that cow parsnip sap also may cause burns or blisters.

Additional Photographs