Giant Hogweed

Heracleum mantegazzianum

ERADICATE

Giant hogweed (Heracleum mantegazzianum) is an aggressive invader that was first introduced to North America as a garden ornamental. It closely resembles our native plant cow parsnip, except the taller giant hogweed can grow up to 6-metres or more.

Family: Apiaceae (Carrot).

Other Common Names: Giant Cow-parsnip, Hogweed.

Origin: Asia.

Growth Form / Reproduction: Herbaceous perennial.  Reproduces by seeds and from perennial buds at crown.

Legal Status: Community Charters Act.

Impacts:
Agricultural: Can infest agricultural areas.
Ecological: Strongly competitive plant; dense stands of very, tall plants outcompete native species in riparian areas. Roots are shallow compared to mixed native communities, which may increase erosion risks in riparian areas.
Human: Sap on exposed skin causes hypersensitivity to sunlight resulting in irritation, blistering and dermatitis. Scarring and blindness may result.

Habitat: Adapted to rich, damp soil and tolerates a wide range of light regimes. Grows on wet to moist disturbed sites at low elevations. Inhabits streams, wetlands, ditches, roads, right-of-ways, agricultural areas, wooded ravines, vacant lots, and other disturbed sites.

Status and Distribution: Present in all CIPC Regional Districts. Widespread in Nanaimo, common in Comox Valley, Cowichan Valley and Strathcona. Limited in Alberni-Clayoquot, Capital and Powell River. Most common in CDFmm and CWHxm but also reported in CWHvm and CWHvh.

Management Strategy: Use protective clothing and eyewear when handling this plant. Cut off flowers to prevent seed formation. Excavate plants, severing roots 8-12 cm below the soil surface. Do not compost; dispose of all plant parts in strong garbage bags. Return to site to check for regrowth. Immature plants can be controlled by covering with black plastic or by mowing at 2 week intervals; 3-5 years of follow-up treatment may be required. Chemical controls can be effective. Foliar applications are most effective in spring followed by a summer application on late appearing sprouts. Stem injections or cut stem and injections are effective after heavy sap flow in spring. No biological control agents are available.

Additional Information:
www.al.gov.bc.ca/cropprot/gianthogw ...