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Agriculture >> Resources >> Insect and Plant Diseases

Giant Hogweed - Heracleum mantegazzianum

Giant hogweed is a large flowering perennial (live for more than two years) that may cause severe skin irritations. Contacting the sap of this plant may increase the sensitivity of some people's skin to sunlight. The resulting dermatitis is more like a burn than a rash and is sometimes referred to as false or artificial sunburn causing painful, burning blisters. Blisters or blotches are likely to develop when sap comes into contact with moist skin in the presence of sunlight. People that have come in contact with this plant have reported symptoms that continue for months!

CONTROL Cutting off the flower heads before they go to seed will prevent the plant from self sowing. If cutting back the plant after seeds have formed, it is important to avoid scattering the seeds. Cut plants after sunset and launder clothing that comes into contact with plant juices. But the roots of the plant may persist and grow. The chemical glyphosate(Roundup) is effective in controlling hogweed. Glyphosate is a non-selective herbicide and will kill any adjacent plants that it comes in contact with.

SIMILAR PLANTS Giant hogweed is a member of the carrot family (Apiaceae). Plants that flower at the same time and may be confused with giant hogweed include Angelica, Queen Anne's Lace, Wild Parsnip, and Common Elderberry. Giant hogweed is distiguishable by its large size, over 6 foot tall, and purple spots on the stem. Only the sap of Wild Parsnip may also cause skin sensitivity in the sun. Click on the pictures below to see larger image.

To report a giant hogweed sighting contact your local Cornell Cooperative Extension. Include the county, township and address or nearest cross road of the plants.

 

Plants in the carrot family (Apiaceae)

	Giant Hogweed Heracleum mantegazzianum	Angelica Angelica atropurpurea	Queen Anne's Lace Daucus carota	Wild Parsnip Pastinaca sativa	Water Hemlock Conium maculatum
Height
	Height 6-12'	Height 4-6'	Height 1-3'	Height 2-5'	Height 4-7'
Flower
	White, flat, up to 20" wide	White, round, 8-12" wide	White, flat 3-6" wide	Yellow, flat, 4-6" wide	White, half round, 2-8"
Stem
	Hairy, thick, purple spots	hairless purple stem	Thin hairy stems	Grooved & yellow-green	Smooth & purple
Leaf
	Lobed leaf, 2-5' wide	Double compound leaf	Finely dissected, up to 6"	Yellow-green, 5-11 leaflets	Double compound leaf
	Giant Hogweed	Angelica	Queen Anne's Lace	Wild Parsnip	Water Hemlock

 

Other plants that you may confuse with giant hogweed
Common Elderberry Sambucus canadensis Height 2-10'	White, flat 4-6"wide		Woody, grey-brown	5-7 leaflets, 2-6" long

 

Wild Parsnip, Pastinaca sativa

Wild Parsnip, is of special concern due to its ability to cause phyto-photo-dermititis (severe sun burn on exposed skin) and its extensive spread along roadways in the southern tier of New York. Wild parsnip is a biennial. The first summer is appears as a rosette of leaves close to the ground. The following year, it sends up a single flower stalk that holds clusters of yellow flowers in flat-topped, umbel. The flower stalks can grow to be more than 4-feet tall. New York State Department of Agriculture and Markets CAPS program (Cooperative Agricultural Pest Survey) is currently identifying locations of Giant Hogweed, however, wild parsnip is not currently being surveyed.

A very effective control method is to cut the entire root just below ground level with a sharp shovel or spade. Cutting below ground level prevents resprouting. In some soil types in wet conditions, the plants can be pulled out of the ground by hand. All seeds must be removed from the site and disposed of in a landfill or by burning. If the population is too large to hand-cut or pull, a power brush-cutter can be used just after peak flowering and before the seeds set. Plants may resprout when cut above the ground, and should be cut again a few weeks later to prevent flowering. Cutting done after seed set will greatly reduce the likelihood that the plants will be able to resprout and flower. Plants cut at this time must all be gathered and removed from the site to prevent mature seed from developing and falling to the ground. Another effective way to eliminate reseeding is to hand-collect all seeds after they have set. If control of flowering or seeding plants is carried out over several years, the population will decrease as the seed bank is depleted.

 

More Information

Giant hogweed is a Federally listed noxious weed.

Please direct all giant hogweed inquiries to the NYSDEC Giant Hogweed Hotline 845-256-3111. The hotline is a place for people to report new
sites, ask questions about the plant and how to control it, and connect with our statewide control project. (Ag & Markets is no longer running the giant
hogweed hotline.)

Another giant hogweed resource is our NYSDEC giant hogweed web page ‘Giant Hogweed’, which provides information about the plant, how to identify
it, how to control it, a map of NY state sites, and more.