Giant Hogweed

Growth Form:  Forb

General:   Biennial, robust and herbaceous. Caution! Do not handle this species with bare hands and skin, sap is photoreactive and may cause severe blishering when exposed to sunlight.

Flowers:   White, clustered atop 50-150 stalks, forming umbrella-shaped cluster to 2.5 ft. wide.

Fruits and Seeds:   Seed heads distributed flat, 1/4 in. wide seeds.

Leaves:   Leaves large, to 6 ft. wide, once compound, leaf stalks spotted with hairs like the stem; leaflets coarsely toothed, deeply cut and pointed at tip.

Stems or Branches:   8-14 ft. high, 1-2 in. thick stems have purple blotches and coarse hairs.

Threatens:   Riparian corridors, fens, seeps, moist savannas, and wet prairies, but may grow in a variety of sunny, moist habitats.

Look-Alikes:   Cow Parsnip (H. maximum, H. lanatum), native, rays 15-30, rarely taller than 2 m. Angelica (Angelica atropurpurea), native, inflorescence hemispherical, leaves twice compound, stems 2-3 m tall, with purplish coloring, not blotches. Wild Parsnip (Pastinaca sativa), exotic invader, yellow flowers, rarely taller than 2 m.

Distribution:   Native to Eurasia, established in NE and NW U.S.

Other Links:  

http://www.kingcounty.gov/environment/animalsandplants/noxious-weeds/weed-identification/giant-hogweed.aspx
http://www.invasive.org/browse/subject.cfm?sub=4536