Page authors: Don Knoke, David Giblin
Heracleum maximum
American cow-parsnip, American hogweed

Distribution: Widely distributed on both sides of the Cascades crest in Washington; Alaska to California, east across North America except in the southeastern U.S.

Habitat: Moist areas, including meadows and forest edge from low to middle elevations.

Flowers: June-August

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern

Pollination: Bumblebees, bees, flies


Robust, single-stemmed perennial from a taproot or a cluster of fibrous roots, 1-3 m. tall.


Leaves large, once ternate, with broad, petiolate, coarsely-toothed and palmately-lobed leaflets 1-3 dm. long and wide, the lateral ones narrower than the central, thinly woolly on the lower surface; petioles sheathing and expanded.


Inflorescence of compound umbels on terminal and axillary peduncles, the terminal umbel 1-2 dm. wide; rays mostly 15-30, up to 10 cm. long; involucre of 5-10 deciduous, narrow bracts, 0.5-2 cm. long; involucel of similar bractlets; pedicels 8-20 mm. long; calyx teeth obsolete, flowers white.


Fruit obovate, 7-12 mm. long and 5-9 mm. wide, strongly flattened dorsally, nearly glabrous, the dorsal ribs narrow, the lateral ones broadly winged.

Accepted Name:
Heracleum maximum Bartr.
Publication: Travels Carolina 344 (1791); cf. Fernald in Rhodora, xlvi. 50 (1944); Rickett in Rhodora,xlvi. 390. 1944.

Synonyms & Misapplications:
Heracleum douglasii
Heracleum lanatum Michx. [HC, IMF3, JPM, VPBC1]
Heracleum sphondylium L. ssp. montanum (Schleich. ex Gaudin) Briq.
Heracleum sphondylium L. var. lanatum (Michx.) Dorn
Pastinaca lanatum
Additional Resources:

PNW Herbaria: Specimen records of Heracleum maximum in the Consortium of Pacific Northwest Herbaria database

WA Flora Checklist: Heracleum maximum checklist entry

OregonFlora: Heracleum maximum information

E-Flora BC: Heracleum maximum atlas page

CalPhotos: Heracleum maximum photos

98 photographs:
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