Giant Hogweed

Arresting this colossal invader through collaboration

Giant hogweed (Heracleum mantegazzianum) was intentionally introduced from Eurasia in the early 1900s as an ornamental garden addition, although it was well-known that the plants contain toxic sap that prevents your skin from protecting itself from sunlight.

On average, an individual plant produces 20,000 seeds, which fall within 10 feet, causing giant hogweed to grow in dense patches and displace native species. The seeds are dispersed short distances by wind but can travel longer distances along waterways, where they can float for up to three days. Giant hogweed frequently spreads along roadsides due to the transportation of seeds during roadway maintenance activities. Seeds can survive for more than five years in the soil.

Since 2017, SEWISC has coordinated control of this gigantic invader, affecting sixteen South Sheboygan neighbors and a nearby railroad right-of-way. Nine consistent years of management have reduced the population to approximately 25 first-year plants. Due to a lack of partner funding in 2022, affected residents independently surveyed their yards, treated individual plants with herbicide, and removed seed heads. SEWISC will continue to collaborate with the affected residents, railroad staff, the City of Sheboygan, the Wisconsin Department of Natural Resources, and NES Ecological Services to monitor and control the populations over the next few years, ensuring the eradication of viable seeds. You can help by learning how to identify and control this threat to our region.