Giant Hogweed

Giant hogweed (Heracleum mantegazzianum) is a very large (up to 15-20 ft), herbaceous, biennial plant native to the Caucasus Mountain region between the Black and Caspian Seas. During the nineteenth centry, it was intentionally introduced to Europe and the United Kingdom as an oramental garden plant, and made its way to the United States in the early twentieth century via the nursery trade (NYSDEC). 


Giant hogweed grows earlier and faster than native vegetation and easily outcompetes native plants for resources which has a negative impact on native wildlife.  In addition, giant hogweed poses a threat to human health as direct skin contact with the plant’s toxic sap induces extreme photosensitivity causing slow to heal burns and scarring. this sap can also cause blindness upon contact with the eyes. Costs are incurred for both medical treatment and efforts to keep the plant under control. Over 100,000 seeds per plant are dispersed annually by water, wind, or humans. Giant hogweed is a designated Federal Noxious Weed.

Image taken from the NYS DEC Giant Hogweed Brochure
Photo provided by APIPP PRISM


Giant hogweed invades disturbed areas across both the Northeast and Pacific Northwestern United States. Although often found in open fields and along roadsides, it has been observed along streams in natural areas.

Distribution in New York State: 

Giant hogweed is found throughout New York State (view a distribution map). 


Giant hogweed begins to emerge in early spring. Their leaves differ depending on the life stage; emerging cotyledons have more rounded leaves that emerge from three thin stems, as the plant matures the leaves become deeply ridged and  compound in arrangement eventually forming a rosette after multiple growing seasons; mature giant hogweed plants can grow between 10-15 feet tall with leaves up to 5 feet wide, flowers are white and umbel shaped, and stems have purple blotches and white course hairs.

Images taken from the NYS DEC Giant Hogweed Brochure

Report Findings: 

  • Take pictures of the entire plant, as well as the stem, leaves, flower and/or seed.
  • Note the location and number of plants.
  • Email ghogweed@dec.ny.gov or call DEC’s Giant Hogweed Information Line at 845-256-3111
  • NYS DEC offers free site visits and management guidance for confirmed giant hogweed sites. 

NYS Department of Environmental Conservation Giant Hogweed Control Program

From late April through August, NYS DEC field crews visit each confirmed giant hogweed site and use the appropriate control method. This is free of charge to the landowner. In general, root-cutting is used at smaller sites with less than 400 plants, the herbicide is used at larger sites with greater than 400 plants and flower/seed head removal is used at all sites to limit seed dispersal. Sites are visited each year until the plants are eradicated. When no more plants are found the site will be monitored for three subsequent years.

For a site to be visited and controlled, landowners must give annual permission. For crews to use herbicide control, landowners must first sign a property permission form. Learn more at the NYSDEC website

Report: ghogweed@dec.ny.gov or call the Giant Hogweed Information Line: 845-256-3111. Provide photos, and detailed directions to the plant infestation (GPS coordinates and street address a plus) and estimate the number of plants.



NOTE: Make sure all skin is covered when working with giant hogweed!

Physical/Mechanical Control: Hogweed is difficult to control due to its toxic effects on the skin.  A small number of plants can be hand dug, but care should be taken to remove most of the roots and to protect skin and eyes.

Repeated mowing does not kill the plant and causes resprouting, but it may weaken the plant if done consistently and persistently enough to starve the roots. Take care to not get sap on skin. 

Chemical Control: Foliar treatments with glyphosate or triclopyr have been effective. Glyphosate is considered the most effective herbicide and should be used in spring and early summer when plants are less than three feet tall. A follow-up application in midsummer may be necessary. Use caution around desirable species since glyphosate is non-selective.


For More Information:

Difficult to control due to damage it posses to skin.  A small number of plants can be hand dug.  Repeated mowing weakens the plants but the large root can remain alive for many years. Foliar treatments with glyphosate or triclopyr have been effective.  Make sure all skin is covered when working with this plant.

Photo Credits:


Prevent the introduction of invasive species into the SLELO PRISM.

Rapidly detect new and recent invaders and eliminate all individuals within a specific area.

Share resources, including funding personnel, equipment, information, and expertise.

Collect, utilize, and share information regarding surveys, infestations, control methods, monitoring, and research.

Control invasive species infestations by using best management practices, methods and techniques to include: ERADICATION (which is to eliminate all individuals and the seed bank from an area), CONTAINMENT (which is reducing the spread of established infestations from entering an uninfested area) and SUPPRESSION which is to reduce the density but not necessarily the total infested area.

Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.

Increase public awareness and understanding of invasive species.

Develop and implement innovative technologies that help us to better understand, visualize, alleviate or manage invasive species and their impacts or that serve to strengthen ecosystem function and/or processes.

Rob Williams                              rwilliams@tnc.org                     Program Director

Megan Pistolese megan.pistolese@tnc.org
Outreach and Education

Brittney Rogers brittney.rogers@tnc.org 
Aquatic Invasive Species

Robert Smith       robert.l.smith@tnc.org 
Terrestrial Invasive Species

Zachary Simek    zachary.simek@TNC.ORG     Conservation and GIS Analyst

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