giant hogweed USDA PLANTS Symbol: HEMA17
U.S. Nativity: Exotic
Habit: Forbs/Herbs
Heracleum mantegazzianum Sommier & Levier

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Taxonomic Rank: Magnoliopsida: Apiales: Apiaceae
Native Range: Caucasus (BAIL);

Appearance
Heracleum mantegazzianum is a herbaceous biennial or monocarpic perennial that can grow up to 15-20 ft. (4.3-5.8 m) in height. The stem is hollow and usually blotched with purple. Both the leaf stalks and stem produce pustulate bristles. The stem can be 2-4 in. (4.8-9.6 cm) in diameter.
Foliage
The leaves are ternate or ternate-pinnate with pinnately lobed lateral segments. They can be up to 9.8 ft. (3 m) in breadth.
Flowers
Heracleum mantegazzianum flowers from June-July. The inflorescence has many white florets (with petals about 0.4 in. [1 cm]) that form a flat-topped umbel. Each inflorescence can have a diameter of up to 2.5 ft. (0.72 m).
Fruit
The fruits are dry and elliptic, measuring 0.3-0.4 in. (8-11 mm) long and 0.25-0.3 in. (6-8 mm) wide. The fruits have brown resin canals that can be up to 0.04 in. (1 mm) in diameter.
Ecological Threat
Heracleum mantegazzianum can outcompete species for habitat, especially in riparian zones, and it may cause increased soil erosion. This plant is on the federal noxious weed list because of its poisonous sap. This sap makes skin very sensitive to UV radiation, causing blistering and severe burns. Caution should be taken when handling this weed. Removing it manually becomes very difficult because of the danger caused by its sap.

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView All Images at Invasive.org


Fruit(s);
Jan Samanek, Phytosanitary Administration, Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
Thomas B. Denholm, New Jersey Department of Agriculture, Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
Terry English, USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Foliage;
Donna R. Ellis, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Infestation;
USDA APHIS PPQ - Oxford, North Carolina , USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Infestation; in flower
Jan Samanek, Phytosanitary Administration, Bugwood.org
Additional Resolutions & Image Usage

Control;
Terry English, USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
Randy Westbrooks, Invasive Plant Control, Inc., Bugwood.org
Additional Resolutions & Image Usage

Foliage;
Jan Samanek, Phytosanitary Administration, Bugwood.org
Additional Resolutions & Image Usage

Stem(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Feature(s); Stem cross-section
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Fruit(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Additional Resolutions & Image Usage

Flower(s);
USDA APHIS PPQ - Oxford, North Carolina , USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Infestation; In winter
Barbara Tokarska-Guzik, University of Silesia, Bugwood.org
Additional Resolutions & Image Usage

Seed(s);
USDA APHIS PPQ , USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Seed(s);
Cesar Calderon, USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
Randy Westbrooks, Invasive Plant Control, Inc., Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
Thomas B. Denholm, New Jersey Department of Agriculture, Bugwood.org
Additional Resolutions & Image Usage

Control;
Thomas B. Denholm, New Jersey Department of Agriculture, Bugwood.org
Additional Resolutions & Image Usage

Damage; Burn caused by plant (left leg, person lying down)
USDA APHIS PPQ - Oxford, North Carolina , USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org
 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.


Invasive Listing Sources:
Commonwealth of Pennsylvania, Department of Conservation and Natural Resources, 1994.
Faith Campbell, 1998
Invasive Plant Council of New York State
Mid-Atlantic Exotic Pest Plant Council, 2005
Native Plant Society of Oregon, 2008
Pacific Northwest Exotic Pest Plant Council, 1998
Virginia Invasive Plant Species List