Sap burns from giant hogweed and wild parsnip: what agencies say
What a New York, a Minnesota and an Ontario agency say about two roadside plants whose sap burns skin in sunlight, where they grow and what the agencies say causes the burn.
Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.
This page reports what the official source says. It is not legal advice: ask the office named here. It is not medical advice and gives no treatment steps. The agencies' own pages cover that. Crews working roadsides, ditches and field edges can meet both plants. The guide on health hazards in tree work covers poison ivy, oak and sumac, and the guide on trees on invasive plant lists covers lists of regulated plants.
The two plants side by side
| Plant | What the agency says |
|---|---|
| Giant hogweed, New York | A very large invasive herb. The agency says its sap can cause painful burns and scarring, and a severe burn within 24 to 48 hours when sunlight and moisture are present, after the plant is brushed against or broken. |
| Giant hogweed, Ontario | The clear watery sap carries toxins that can cause severe skin inflammation. The page says painful blisters appear within 48 hours and that purplish scars may last for many years. |
| Wild parsnip, Minnesota | The page calls skin burns from contact with the sap the largest concern. Sap on skin in sunlight can cause a chemical burn that may resemble a blistering rash with discoloration. |
Giant hogweed in New York
The New York State Department of Environmental Conservation giant hogweed page opens with a bold warning not to touch the plant. It describes a biennial or perennial herb of the carrot family that can grow to 14 feet or more, with hollow ridged stems 2 to 4 inches across carrying dark reddish-purple blotches, compound leaves up to 5 feet wide, and white flower heads up to 2 1/2 feet across. It says giant hogweed is a federally listed noxious weed and that state law bars possessing it with the aim of selling, importing, buying, moving, introducing or propagating it. The page has a lookalikes table. It lists cow parsnip and angelica as plants that may cause burns, and gives size, flower and leaf differences. Giant hogweed flowers late June to mid July in that table.
Giant hogweed in Ontario
The Ontario government's giant hogweed page says the plant is a garden ornamental from southwest Asia that is becoming more common in southern and central Ontario. It says it grows along roadsides, ditches and streams and invades old fields and open woodlands, with a scattered distribution south of a line from Manitoulin Island to Ottawa. It gives a height of up to 5.5 metres under ideal conditions. It says seeds can stay viable in the soil for up to 15 years. On health, it says eye contact has been reported in the media to cause temporary or permanent blindness, but evidence of permanent blindness linked to exposure cannot be substantiated by existing research.
Wild parsnip in Minnesota
The Minnesota Department of Natural Resources page on wild parsnip says the non-native plant was first found in the state in the 1990s and grows in open places, naming roadsides, pastures, disturbed areas, right-of-ways, abandoned fields and forest edges, and says shade does not suit it. It describes a two-year life cycle: a low rosette of leaves in the first year, then a flowering stalk about 4 feet tall with flat-topped yellow flower clusters that bloom from June to late summer. The page gives the medical name phytophotodermatitis for the burn. It says seeds can survive in the soil for up to four years.
What the pages do not say
None of the three pages is written for tree crews. The Ontario page names the Invading Species Hotline at 1-800-563-7711 for people who think they have giant hogweed on their property or see it in their community. The New York page names the DEC Invasive Plant Information Line at 845-256-3111 for reports, and the Minnesota page names Report a Pest at 1-888-545-6684. The New York and Minnesota pages are about their own states' laws and conditions.