Beyond its impressive size, Giant Hogweed is notorious for its sap effects on skin - worse and longer lasting than than poison ivy. The sap sensitizes skin to the suns UV rays within 15 minutes, causing blisters to form within 24-72 hours, which can leave scars behind lasting months to years. The affected areas often remain sensitive to UV light, potentially leading to a recurrence of blisters years later. Even worse, if the sap if gotten in the eye, it can cause blindness.
The N.Y. Department of Health recommends that if the sap contacts skin, it be washed off with cold water immediately and either apply sunscreen or cover up the affected areas since this can prevent further reactions. The toxic reaction can begin as soon as 15 minutes after contact. If Hogweed sap gets into the eye, rinse with cold water immediately and put on sunglasses.
Giant Hogweed also is considered invasive, and quickly crowds out native species in areas it colonizes. In a dominant stand, up to 80% of incoming light is absorbed by its large leaves and flowers, shading out any species which fall under its canopy.
According to the NY DEC, the plant grows in New York, Pennsylvania, Connecticut, Ohio, Maryland, Oregon, Washington, Michigan, Virginia, Vermont, New Hampshire and Maine.
Hogweed control is difficult; it produces a prodigal amount of seeds, between 20,000 to 100,000 per year, which can remain viable for upto 7 years in the soil. Additionally, its large root can survive multiple cuttings. Control using multiple applications of herbicide over a few growing seasons is most successful. Additional info here:
Giant Hogweed in CT
Giant Hogweed Control
Hogweed Control
The Giant Hogweed Best Practice Manual, (available in multiple languages):
