ST. LAWRENCE EASTERN LAKE ONTARIO PARTNERSHIP FOR REGIONAL INVASIVE SPECIES MANAGEMENT
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 century, it was intentionally introduced to Europe and the United Kingdom as an ornamental 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.
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.
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
Control/Management:
Before beginning giant hogweed control, refer to DEC’s Giant Hogweed Control Guide (PDF) for safety precautions, step-by-step explanations of control methods, information on monitoring, and best management practices. 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.
PREVENTION
Prevent the introduction of invasive species into the SLELO PRISM.
EARLY DETECTION & RAPID RESPONSE
Rapidly detect new and recent invaders and eliminate all individuals within a specific area.
COOPERATION
Share resources, including funding personnel, equipment, information, and expertise.
INFORMATION MANAGEMENT
Collect, utilize, and share information regarding surveys, infestations, control methods, monitoring, and research.
CONTROL
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.
RESTORATION
Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.
EDUCATION & OUTREACH
Increase public awareness and understanding of invasive species.
INNOVATION
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.