Page authors: Don Knoke, David Giblin
Sium suave
water parsnip, hemlock water-parsnip

Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.

Habitat: Swampy places and shallow water of lakes, ponds, and backwater channels, from low to middle elevations.

Flowers: July-August

Origin: Native

Growth Duration: Perennial

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.

Accepted Name:
Sium suave Walter
Publication: Fl. Carol. [Walter] 115. 1788.

Synonyms & Misapplications:
Sium cicutifolium Schrank
Sium floridanum Small
Sium suave Walter var. floridanum (Small) C.F. Reed
Additional Resources:

PNW Herbaria: Specimen records of Sium suave in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Sium suave checklist entry.

E-Flora BC: Sium suave atlas page.

CalPhotos: Sium suave photos.

USDA Plants: Sium suave information.

29 photographs:
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