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Invasive Species of Concern in Maryland
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April 2003

May 20 Workshop Slated to Build Awareness
Giant Hogweed

Contact: Don R. Robbins | 410-841-5920

Giant Hogweed
Photo: A. Gibbs, Maine Department of Agriculture

ANNAPOLIS, MD (April 2, 2003) - Beware of the Giant Hogweed, a giant perennial plant named by the Maryland Invasive Species Council(MISC) as April's "Invader of the Month." While interesting for its unusually large size and flower, the Giant Hogweed is on the federal noxious weed list because of its potential as a public health hazard. The plant has been found in neighboring Pennsylvania and Washington D.C., but not in Maryland. "Giant Hogweed exudes a clear, watery sap that causes the skin to become photosensitive to ultraviolet radiation," said Don R. Robbins, weed control administrator for the Maryland Department of Agriculture. "Contact with the sap can result in severe burns, blisters and dermatitis, possibly leading to future complications, namely skin cancer, which is the primary reason for concern in Maryland." Giant Hogweed (Heracleum mantegazzianum) is an escaped ornamental that was introduced into the United States as a garden curiosity. It may also have been brought into this country for its fruit, which is used as a spice (golmar) in Iranian cooking. Native to the Caucasus Mountains and southwest Asia, it is related to carrots and parsley and was cultivated in North America as early as 1917. Under U.S. Department of Agriculture (USDA) regulations, introduction of the plant into the United States is illegal as is interstate and intrastate movement. Giant hogweed may colonize a wide variety of habitats, but it is most common along road sides, vacant areas, streams and river edges. It is a perennial and, as its name indicates, is characterized by its size and may grow to 15 or 20 feet in height. Giant Hogweed is further distinguished by a stout dark reddish purple stem and spotted leaf stalks that are hollow and produce sturdy bristles. Stem size varies from 2-4 inches in diameter with deeply incised compound leaves that grow up to 5 feet in width. It has a tap root or, occasionally, a fibrous root.

Giant Hogweed flowers mid May through July with numerous white flower clusters that are shaped like an umbrella (up to 2.5 feet in diameter). The plant produces flattened, 3/8 inch long, oval, dry fruits that have a broadly rounded base and broad marginal ridges. If you think you see this plant, avoid contact with sap and report it to the Maryland Department of Agriculture Weed Control office. The Maryland Department of Agriculture, in cooperation with USDA Animal Plant Health Inspection Service, will be conducting a workshop on May 20, 2003, at the Howard County Fairgrounds to build awareness about the Giant Hogweed. The workshop is for surveyors, foresters, landscapers, landowners and others who are likely to be along roadsides, streambeds and forest edges and other areas known to be favorable habitat. To make reservations for the workshop, for more information about the Giant Hogweed, or to report the presence of the plant, contact Don Robbins at 410-841-5932. For more information about the Giant Hogweed and other invasive species of concern, visit the MISC website at http://www.mdinvasivesp.org. Invasive species of many types present a threat, second only to habitat loss, to the conservation of desirable animals, plants and their environments.

Note: Photo and descriptive brochure available electronically upon request.

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