Download MSdoc - Stevens County

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
Photo by Donna R. Ellis, Univ. of Connecticut
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
Photo by Terry English, USDA APHIS PPQ

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
Control
Where found – No known plants or infestations in Stevens County, but is known in W.WA
Stevens County Noxious Weed Control Board, February 2007