Invasive Plants and Agricultural Pest Management
Welcome to Alaska's Invasive Plant Program. Our program coordinates prevention, outreach, and management strategies for invasive plant issues through collaboration with land managers, agencies, organizations, and policy makers across Alaska. These efforts are guided by the implementation of our Strategic Plan and relevant noxious weed regulation and policy. Our goal is to help keep Alaska's pristine landscapes and natural resources free from impacts of noxious and invasive plants.
Giant hogweed (Heracleum mantegazzianum)
First federally listed noxious weed in Alaska
- Taking Action
Grows up to 10-15 feet tall
Leaves are large, compound, and dissected measuring up to 3-5 feet wide
Umbel inflorescence grows up to 2.5 feet across
Flowers are small and white to light pink
Stems are hollow and have dark red or purple spots and bristles
It produces a watery sap that can cause severe dermal injury to humans, birds, and other animals
**This plant closely resembles native cow parsnip but can be distinguished by larger inflorescence size, deep leave dissection and overall plant height.
Giant hogweed reproduces by both seed, up to 50,000 per plant, and but fragmented roots. Due to its giant size, it has the potential to form dense canopies that enable it to outcompete and displace native riparian vegetation. The plant produces a watery sap that can cause severe blistering and burning of the skin, impacting human health and negatively impacting environmental resources.
In Alaska, there has only been one documented occurrence of giant hogweed in Kake. This infestation site has been successfully eradicated, and continually monitored.
Habitat: Riparian areas, river banks, streams, roadsides, gardens, and waste areas
If you think you have seen giant hogweed, report the site by calling 1-877-INVASIV.
Manual control must be taken with caution because of the toxic watery sap the giant hogweed produces. Always wear protective equipment when handling this plant. Manually remove by cutting roots at least 3-4 inches below the surface. Mowing repeatedly will also control this plant. Systematic herbicides may also be effective.