Acorus americanus
American sweetflag, several-vein sweetflag

Distribution: Very limited distribution in Washington along eastern border with Idaho; widely distributed throughout northern half of North America from Alaska to Newfoundland.

Habitat: Wetlands, lake margins, and riparian zones.

Flowers: May-July

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern


Herbaceous perennials; rhizomes branched, creeping horizontally at or near surface; emits distinctive and pleasant odor when bruised or broken.


Leaves bright green, basally white with pink or red, sword-shaped; venation parallel along length of blade, prominent veins 2-6; swelling in center evident in cross section, tapering toward both ends; vegetative leaves to nearly 1.5 m, sheathing base 18-52 cm or more, distal portion of leaf generally 31-89 cm long and 0.3-1.2 cm broad, margins entire; sympodial leaf typically 57-148 cm long, usually equal to or slightly longer than vegetative leaves, sheathing base 25-75 cm long, distal portion 28-78 cm long and 0.3-1.3 cm broad.


Inflorescence a solitary spadix, from 3-angled axis, spadices 3.3-7.4 cm long and 4.7-10 mm broad during flowering period, 3.5-8 cm long and 7-18.2 mm broad when in fruit, nearly cylindric, tapering, apex obtuse; distal sympodial leaf extending beyond spadix; true spathe absent; flowers 2-3 mm; tepals 6, light brown; stamens 6, distinct; anthers yellow, turning inward toward flower center; pollen grains usually deeply staining in aniline blue; ovaries 1, green, usually 3-chambered, sessile; stigmas sessile, minute.


Berries, shaped like upside down pyramids, 4-6 mm; seeds usually 6, tan, slenderly oblong to obovate, 3-4 mm.

Accepted Name:
Acorus americanus (Raf.) Raf.
Publication: New Flora and Botany of North America. 1: 57. 1836. 1836.

Synonyms & Misapplications:
Acorus calamus L. var. americanus Raf.
Acorus calamus L. var. americanus H. Wulff
Additional Resources:

PNW Herbaria: Specimen records of Acorus americanus in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Acorus americanus checklist entry.

E-Flora BC: Acorus americanus atlas page.

CalPhotos: Acorus americanus photos.

USDA Plants: Acorus americanus information.

1 photographs:
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