Heracleum mantegazzianum is a biennial to short-lived perennial herb, fflowering only once (monocarpic), to 5 m tall, sap sensitizes skin to UV radiation, can cause severe dermatitis; stems to 10 cm thick, with purplish spots.
Leaves alternate, leaf stalk inflated, blade to 3 m long, 80 cm or more wide, triangular in outline, deeply pinnately divided, divisions to 130 cm, lobed and toothed, tips pointed.
Flowers white, petals to 1 cm long, in very large umbrella-shaped clusters to 75 cm wide with 50-150 rays, summer.
Fruit dry 0.8-1 cm long, strongly flattened, elliptic, lateral ribs winged.
Wetland status: UPL.
Frequency in NYC: Very infrequent in NYC but an invasive in other parts of NYS.
Habitat: Open, disturbed soil, riverbanks, ditches.
Notes: Introduced as an ornamental in 1917 (Douce et al. 2007). Federally listed as a noxious weed (Douce et al. 2007). Listed by the Invasive Plant Council NYS and IPM Program of Cornell University as an invasive in northern several states (Allee 2000; Uva et al. 1997). See USDA hogweed fact sheet: ttp:www.ceris.purdue.edu/napis/pests/ghw/facts.txt.