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.

Flowers: June-August

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern

Edibility: EXTREMELY TOXIC EVEN IN SMALL AMOUNTS WHEN INGESTED BY HUMANS AND LIVESTOCK.

Pollination: Generalist

Perennial herbs, 10--15 dm, stems usually purple spotted below; axillary bulbils absent.

1-2-ternate-pinnately compound; leaflets linear to ovate, often with dark, shiny petiolule, 14-104 x 2-39 mm, areoles on abaxial leaf surface usually rounded or square, margins serrate, abaxial surface glabrous.

Umbels, terminal and axillary, compound, flat topped, convex, or hemispheric; peripheral flowers not different; involucral bracts narrow, herbaceous, or absent; involucel bractlets present, rarely absent.

Hermaphroditic; sepals reduced; petals white.

Schizocarps, widely elliptic to circular, 2.3--4.1 x 1.6--3.4 mm, commissure unevenly or not constricted; dorsal corky thickened ribs equaling to narrower or slightly wider than oil ducts in intervals between ribs on mature fruits.

EXTREMELY TOXIC EVEN IN SMALL AMOUNTS WHEN INGESTED BY HUMANS AND LIVESTOCK.