Giant hogweed
Heracleum mantegazzianum                  Parsley Family

Key identifying traits

• Huge plant growing 15 to 20’ tall
• Plants have a stout, dark reddish-purple stem and spotted leaf stalks
• The 2-4”stems & stalks are hollow
• Leaves are compound with three deeply incised leaflets & may be as large as 5’ wide
• Flowers are a broad flat-topped umbel composed of many small white florets; may be 2 ½’  wide
•  Can be confused with cow parsnip which is a much smaller native species

Biology and ecology

• A biennial or perennial plant tuberous rootstocks
• The plant exudes a clear watery sap which can cause severe burns to the exposed areas
• Giant hogweed is native to the Caucasus mountain region of Eurasia & southwestern Asia; it has been introduced to many areas as a garden ornamental
• Giant hogweed may colonize a wide variety of habitats but is most common along rights-of-way, vacant lots, streams, and rivers
• It has been put on the federal noxious weed list; transporting or moving this plant is illegal

Control

Prevention – Learn to identify plants; start monitoring early in the season, do not plant ornamentals known to escape or be invasive

Biological – No known biological control in our area but cows and pigs have eaten it with no apparent harm

Cultural – Hogweed will crowd out other plants

Mechanical – Plants can be dug out but protective clothing and eyewear should be worn; mowing stimulates the bud growth on the rootstalks

Chemical – Glyphosate or simazine are recommended for control: refer to the PNW Weed Management handbook for specific chemical recommendations

Photo by Donna R. Ellis, Univ. of Connecticut

Photo by Terry English, USDA APHIS PPQ

Photo by Donna R. Ellis, Univ. of Connecticut

Where found – No known plants or infestations in Stevens County, but is known in Western WA.

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