Giant Hogweed

Giant hogweed (Heracleum mantegazzianum) is a VERY LARGE, invasive plant that can cause painful burns and scarring. Brushing against or breaking the plant releases sap that, combined with sunlight and moisture, can cause a severe burn within 24 to 48 hours. Giant hogweed is a Federally listed noxious weed and NYS law prohibits its possession with the intent to sell, import, purchase, transport, introduce or propagate. Learn more about what to do if you touch giant hogweed.

Description

Giant hogweed is a biennial or perennial herb in the carrot family (Apiaceae) which can grow to 14 feet or more. Its hollow, ridged stems grow 2-4 inches in diameter and have dark reddish-purple blotches. Its large compound leaves can grow up to 5 feet wide. Its white flower heads can grow up to 2 1/2 feet in diameter. Some other plants look very similar.

Giant Hogweed and Lookalikes

Giant Hogweed and Common Lookalikes

Plant	Flower	Leaf	Stem
Giant Hogweed   7-14 feet tall   This plant can cause burns.   Do not touch.	White umbrella-shaped flower clusters   up to 2.5 feet wide. 50+ rays per cluster.   Flowers late June - mid July	Compound, lobed, deeply incised,   up to 5 feet wide	Green with purple splotches and coarse   white hairs - thick circle of hairs at base of   leaf stalk, 2-4 inches in diameter.
Cow Parsnip   5 to 8 feet tall   This plant may cause burns.	White flat-topped flower clusters no longer   than one foot wide. 15-30 rays per cluster.   Flowers late May - Late June	Compound, less incised than hogweed,   between 2 - 2.5 feet wide	Green and rigid with fine white hairs   1-2 inches in diameter.
Angelica   4 to 9 feet tall   This plant may cause burns.	Softball-sized and shaped clusters,   greenish-white or white   Flowers mid May - mid June	Compound leaves that may extend   up to 2 feet wide	Smooth, waxy purple, 1 to 2.5 inches   in diameter (no hairs or bristles)
Wild Parsnip   Up to 5 feet tall   Native of Eurasia   This plant can cause burns.   Do not touch.	Single flower stalk with flat-topped   umbel of yellow flower clusters   Flowers late May - early July	Compound, pinnate, 5 to 15 toothed   leaflets, variably lobed, yellowish-green	Yellowish-green with full length   grooves (no hairs or bristles)
Queen Anne's Lace   1 to 3 feet tall   Native of Eurasia	Flat-topped umbel of white flower clusters,   2 to 4 inches wide. The central flower   cluster usually deep purple.   When fruiting, the umbel becomes   concave and resembles a "bird's nest."	Compound, pinnate, fern-like.	Green, covered with bristly hairs.
Poison Hemlock   4 to 9 feet tall   Native of Eurasia   All parts of this plant are very poisonous.   DO NOT INGEST	Small and white arranged in numerous   flat-topped clusters on all branches   Flowers late May - late June	Bright green, small and fern-like,   may appear glossy	Smooth and waxy stem with purple   blotches, 1 to 2 inches in diameter   (no hairs or bristles)
Common Elderberry   Shrubs 5 to 12 feet tall   Spreads and forms thickets	White flat-topped or slightly rounded flower   clusters at branch ends, 2 to 6 inches   wide. Fruit is purple to black in color.   Flowers June - July	Compound, pinnate, 5 to 11 toothed leaflets	Older woody stems or young green stems   with prominent lenticels (pores), no hairs   or bristles
Pokeweed   Up to 10 feet tall   All parts of the plant are poisonous.   DO NOT INGEST	Greenish-white racemes (linear flower   clusters), with dark purple berries.   Flowers late June - October	Alternate, large, entire leaves (not leaflets)	Green to red or purplish, smooth   stout stems, no hairs or bristles

Distribution and Habitat

Giant hogweed is a native of the Caucasus Mountain region between the Black and Caspian Seas. It was introduced to the United States in the early twentieth century as an ornamental garden plant. It has become established in New England, the Mid-Atlantic Region, and the Northwest. Giant hogweed grows along streams and rivers, as well as in fields, forests, yards, and near roadsides. It prefers sunny areas and moist soils and can also grow in partial shade.

Environmental Impacts

Giant hogweed can grow in dense patches which crowds out and replaces native plants. Their large leaves can also shade out surrounding plants, leaving bare soil beneath them leading to soil erosion. Soil erosion is of special concern along stream banks and slopes where giant hogweed grows because the roots do not hold soil as well as native plants.

Spread

On average, a giant hogweed plant produces 20,000 seeds, with some plants producing up to 100,000 seeds. Most seeds fall within 10 feet of the parent plant, causing giant hogweed to grow in dense patches. The seeds are dispersed short distances by wind but can travel longer distances by water, where they can float up to three days. For this reason, giant hogweed is most commonly spread along rivers, streams, and other waterways. Giant hogweed is also often spread along roadsides when seeds are transported by mowers or construction equipment. Seeds can survive for more than five years in the soil.

Historically, gardeners planted giant hogweed for its impressive size and large flowers, causing it to be introduced throughout the New York State. Currently, it is a prohibited plant under NYS Regulation 6 NYCRR Part 575.

Safety Information

How Giant Hogweed Causes Burns

•  All parts of the giant  hogweed plant contain toxic sap that prevents your skin from protecting itself from sunlight.
• The sap contains harmful chemicals called furanocoumarins that when combined with sunlight can cause phytophotodermatitis; a serious skin inflammation.
• Heat and moisture (sweat or dew) can worsen the skin reaction.
• The reaction can begin as soon as 15 minutes after getting sap on your skin and can result in painful blisters that form within 48 hours and become dark and pigmented.
• Lasting impact of giant hogweed burns may include scars that last up to six years (though typically only last a few months) and long-term sensitivity to sunlight.

Take Precautions When Working Near Giant Hogweed

• Do not touch the plant with bare skin. The photosensitizing chemicals are present in all parts of the plant and burns can result from even lightly brushing against the foliage, stem, flower, or seed.
• Apply sunblock and wear long, waterproof gloves; long sleeves; pants; boots; and eye protection when working near or with giant hogweed. When possible, wear synthetic water-resistant materials (e.g., dishwashing gloves, a rain suit or TyvekTM suit, and rubber boots).
• Keep water, soap, and eyewash near your work area in case of exposure to sap.
• Maintain distance from others when controlling giant hogweed as sap can splash three to four feet when plants are cut or damaged. To avoid increased exposure to sap, DO NOT use a “weed-whacker” or brush cutter.
• When removing contaminated protective gear and work clothes, take care not to touch your skin.
• Wash equipment with soap and water and launder work clothes.
• If you cannot shower immediately after performing control activities, wash as best as you can on site and take a full shower as soon as possible, then limit your exposure to sunlight for the rest of the day.
• Additional precautions: consider wearing a face shield to protect against touching your face with sap-covered gloves, work after sunset or when the work area is shaded to limit sun exposure.

What to Do if You Come in Contact With Giant Hogweed 

• Wash the affected area thoroughly with soap and water as soon as possible;
• Keep exposed area covered and protected from sunlight for 48 hours; 
• See a physician if you have a reaction or any questions;
• If a reaction occurs, topical steroids applied early can reduce the severity of the reaction and ease discomfort;
• If sap goes in eyes, rinse them with water, wear sunglasses or cover your eyes, and seek medical care; and
• If a reaction has occurred, it is important to protect the skin from the sun until it is fully healed, which can take several years. Protect skin by applying sun block or cover the affected area when possible.

Management

From late April through August, DEC field crews visit each confirmed giant hogweed site, and use the appropriate control method. This is free of charge to the landowner. In general management is decided by the size and number of plants:

• root-cutting is used at smaller sites with less than 400 plants,
• herbicide is used at larger sites with greater than 400 plants; and
• flower/seed head removal is used at all sites to limit seed dispersal.

Sites are visited each year until the plants are eradicated. When no more plants are found the site will be monitored for three subsequent years.

For a site to be visited and controlled, landowners must give annual permission. For crews to use herbicide control, landowners must first sign a property permission form.

Past years' annual reports:

• 2023 Giant Hogweed Program Annual Report (PDF)
• 2023 Giant Hogweed Program Annual Summary (PDF)

What You Can Do To Help

Report Giant Hogweed

If you think you see giant hogweed, take photos of different parts of the plant (the entire plant, stem, leaves, and flowers/seed) while keeping a safe distance. Then, confirm identification and email DEC or call the Giant Hogweed Information Line: 845-256-3111. Provide photos, detailed directions to the plant infestation (GPS coordinates and street address preferred) and estimate the number of plants.

DEC has giant hogweed publications for distribution. Email DEC or call the Giant Hogweed Information Line at 845-256-3111 to let us know how many brochures and posters you can use. Provide your mailing address so we can mail them to you.

• Giant Hogweed Poster (PDF) - available in two sizes. 18' x 24' and 12' x 16'
• Giant Hogweed Brochure (PDF)
• Giant Hogweed Brochure (Spanish) (PDF)
• Giant Hogweed Poster (Spanish) (PDF)