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Annual or biennial, slightly aromatic herb, from a taproot; stems erect, grooved, glabrous, branched above, 0.3-2.0 (rarely 3.0) m tall.
Stem leaves pinnately to bipinnately cut, glabrous, stalked, the segments lanceolate and sharp-toothed, 5-15 cm long.
Heads discoid, numerous in a compact spikelike inflorescence, short-stalked; involucres hemispheric, 2-3 mm tall; involucral bracts glabrous, the outer ones narrow and green, the inner with only a green midrib and broad, thin, dry, slightly papery margins; receptacles glabrous; female flowers fertile; disk flowers fertile.
Achenes 4-5-nerved, glabrous.
Source: The Illustrated Flora of British Columbia