Distribution: Occurring east of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.
Habitat: Marshes, ditches, and shorelines, from low to middle elevations in the mountains.
Growth Duration: Biennial, Perennial
Conservation Status: Not of concern
Edibility: EXTREMELY TOXIC EVEN IN SMALL AMOUNTS WHEN INGESTED BY HUMANS AND LIVESTOCK.
Annual to perennial herb, rarely a shrub or tree, generally from taproot; stems generally scapose, generally ribbed, hollow.
1-4 dm long, ovate to triangular-ovate, 1-2 or pinnate; leaflets 2-10 cm, lanceolate, acute or acuminate, coarsely to sparsely serrate, major veinlets on abaxial surface, generally circular or square, less often elongate.
Umbels compound, terminal and lateral; peduncles 2.5-12 cm; rays number 15-30, 2-4.5 cm each; pedicels number 15-30, 2-10 mm long.
Mericarps 3-4 mm long, generally ovate; rib width generally greater than intervals between.
EXTREMELY TOXIC EVEN IN SMALL AMOUNTS WHEN INGESTED BY HUMANS AND LIVESTOCK.