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Giant Hogweed

Submitted by Chief on 12/Jul/2010
24.58.132.69

Message:

Giant Hogweed

Background:

Heracleum mantegazzium, known as Giant Hogweed in popular vernacular, originated in Asia. It originally was cultivated in Victorian times, based on its impressive height and size of the plants, its leaves and its flowers.

In North America it has become a difficult to eradicate following its introduction as a cultivar in Highland Park, Rochester, in 1917. It is an invasive weed, most commonly found in moist soils along roadside ditches, stream banks, etc.

Identification:

Giant Hogweed is a member of the parsley and carrot family of plants.

It may attain a total height of 6 – 15 feet, making it the tallest herbaceous plant found in New York State. Its leaves range between 2 and 5 feet in total span! Its thick stem ranges from 2 to 4 inches in diameter, and is hollow. The stem is colorful, being predominately green, with areas of deep purple coloration. The stem, leaf and flower stalks are covered abundantly with hair, most notably at the base of the leaf stalks. Its small white flowers are maintained in wide, flat clusters that may approach 2.5 feet across.

Giant Hogweed flowers from mid-June to mid-July. At the conclusion of flowering, the flowers are replaced by small, green fruit, that quickly turn brown, before falling off to seed the ground. The plant is locally invasive as well, and will often regrow from cut off rootstock.

It may be confused with other members of the carrot family (Apiaceae), specifically: Angelica, Queen Ann’s Lace, and Wild Parsnip.

Angelica is differentiated by having a hairless purple stem with a plant height of 4 – 6 feet maximum, double compound leaves, and rounded white flowers that only reach 1 foot across.
Queen Ann’s Lace is differentiated by having thin stems, which are covered by hair, with a plant height of only 1 to 3 feet, fine (fern-like) leaves of 6 inches or less in span, and flat white flowers of 3 to 6 inches across.
Wild (Cow) Parsnip is differentiated by having grooved yellow-green stems, with a plant height of 2 to 5 feet, yellow-green leaflets, and flat yellow flowers of 4 to 6 inches across.

Health Effects:

Giant Hogweed produces secretions of clear, watery consistency that can cause contact reactions to skin and mucous membranes in a subset of the population. The secretions (sap) produced contain furocoumarins (Clarke, 1975), which sensitize the skin in some individuals to sunlight. A phyto-photo-dermatitis occurs, usually several days after exposure, which results in edema, vesicals, and bullae; more resembling burns than a typical contact dermatitis (Drever & Hunter, 1970).

Serious, potentially fatal reactions have occurred in the past when children played with the hollow stems of the plants, using them as pea shooters/telescopes. This has resulted in significant reactions involving the mucous membranes, which have resulted in airway occlusion.

If the skin reactions result in more than a partial thickness burn, permanent scarring may result, which is usually purple or black in color.



Treatment:

Those with involvement of the mucous membranes (oral) should s*** on ice chips/use ice compresses for 15 minute intervals 4 times daily, followed by an application of a medium potency steroid, such as Synalar.
If the pain is not controlled, 2% viscous xylocaine solution may be swished around in the mouth for 5 minutes, every 3 or 4 hours. For more severe cases, 40mg of triamcinolone (Kenalog) given once intramuscularly may be employed for an average sized adult.

For those with involvement of the skin, compresses of aluminum acetate (Burow’s solution), or concentrated boric acid solution may offer relief. Synalar may be applied topically to ease symptoms. Topical antihistamines have been found to not be helpful. For more severe cases systemic corticosteroids may be employed.


Control:

When working with Giant Hogweed wear disposable rubber gloves, long sleeve shirts and pants.
The chemical glyphosate (Roundup) is effective when applied during the growing season (before the plant flowers).

If the plant has flowered, cut off the flower heads before they set seed. The plant, along with its roots may then be removed. Plants can regrow from chopped off roots, so it is important to attempt to get as many as possible. Giant Hogweed is locally invasive, so its roots may extend for considerable distances in the soil.

If the seed has dispersed watch the general area for new plant growth, which may be delayed for as many as 7 to 8 years!

From: John Ingham [mailto:john@health.co.lewis.ny.us]
Sent: Friday, July 02, 2010 11:37 AM
To: Jim Martin (E-mail); Michele Ledoux (E-mail); Mark Tuttle (E-mail); Nick Hanno; Fred Munk
Cc: Carol Paluck (E-mail)
Subject: Giant Hogweed



Giant Hogweed seems to be a public health problem in areas of NYS this summer. See the attached map and general information.

There have been a few reports to LC Public Health of the weed being in the southern part of the county. According to the map it seems to be spreading.

I would like to gather any available information concerning Giant Hogweed in Lewis County.

Please let me know if you are aware of any human contacts with the plant, sightings, or complaints by the public and, also, any public information/education or eradication efforts concerning Giant Hogweed that are currently underway in the county.

Thanks,

John

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