GIANT HOGWEED
Heracleum mantegazzianum

THREAT: A native of the Caucasus Mountains of Asia, giant hogweed has been introduced as an unusual garden ornamental. Giant hogweed represents a threat to both public health and the environment. When skin contact occurs in the presence of sun-exposure, a glucoside contained in the sap of the plant can cause severe skin irritations, burns, and large watery blisters. The scars left behind can be permanent. In the environment, plants are now escaping home gardens and becoming problematic in riparian areas, excluding native vegetation and causing erosion problems.

DESCRIPTION: The most impressive characteristic of giant hogweed is its massive size. Plants reach a height of 10 to 15 feet. Its stout, hollow stems are 2 to 4 inches in diameter. The stems are covered with coarse, white hairs and purple blotches. Large, incised compound leaves can expand to 5 feet across. Numerous, small white flowers cluster to make an umbrella-shaped inforescence which is 2 to 3 feet in diameter. It is found along roadsides, gardens, vacant lots, barnyards, orchards, streams, and rivers.

MANAGEMENT OPTIONS: Large, tuberous roots, rapid growth and abundant seed production make giant hogweed difficult to control. Small numbers of plants can be hand-dug. If hand-digging, protective clothing should be worn to avoid contact with the sap. Immediate washing of the skin should be done if contact does occur. Not everyone experiences skin irritation. Repeated mowing during the season weakens plants, but the tuberous roots can remain alive for many years. It is important to recognize giant hogweed and not spread it through garden use or by collecting and drying the flower heads. Some chemical controls are effective. Contact the Weed Control Board for site-specific control recommendations.