Distribution: Southern British Columbia to central California, east to Newfoundland and Virginia.
Habitat: Swampy places and shallow water, in the valleys and foothills.
Flowers: July - August
Conservation Status: Not of concern
Glabrous perennial form a short crown and fibrous roots, the roots also sometimes originating at the node above the crown; stem solitary, stout, ribbed, 5-12 dm. high, branched above.
Leaves alternate, usually basal and cauline, the lower long-petiolate, the petioles winged and progessively shorter upward, the blades pinnately compound with 7-13 sessile leaflets, serrulate to deeply pinnatifid and again cleft, the leaflets 2-9 cm. long and 1.5-10 mm. wide.
Inflorescence of compound umbels; involucre of 6-10 lanceolate or linear bracts 3-15 mm. long, entire or incised, unequal, reflexed; involucel of 4-8 narrow bractlets 1-3 mm. long; rays of the umbels 10-30, 1.5-3.5 cm. long; calyx teeth minute; flowers white.
Fruit glabrous, broadly elliptic to orbicular, 2-3 mm. long.