Page authors: Don Knoke, David Giblin
Acmispon americanus
American bird's-foot trefoil
WTU specimens
Other herbaria
WTU images

Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east to Rocky Mountains, south to Mexico.

Habitat: Chiefly in sandy to rocky, exposed or wooded areas, more common at low elevations

Flowers: April-September

Origin: Native

Conservation Status: Not of concern


Villous-pubescent annual, the stems 1-6 dm. tall, erect to decumbent.


Leaves sub-sessile, trifoliate, or the upper leaves simple; leaflets lanced-ovate to oblong-obovate, 6-30 mm. long and 3-10 mm. broad; stipules gland-like.


Peduncles axillary, 5-30 mm. long, with a small, simple bract just below the single flower; flowers pea-like, 4-8 mm. long, pale yellow or cream, usually reddish-tinged; calyx 3-6 mm. long, the 5 linear teeth up to twice as long as the tube.


Pod 15-35 mm. long and 2-2.5 mm. broad, slightly constricted between the 4-8 seeds.

Accepted Name:
Acmispon americanus (Nutt.) Rydb.
Publication: Bull. Torrey Bot. Club 40: 45 (1913). 1913.

Synonyms & Misapplications:
Lotus americanus (Nutt.) Bisch., homonym (illegitimate)
Lotus purshiana (Benth.) Clements & Clements, orthographic variant [HC]
Lotus purshianus Clem. & E.G. Clem.
var. americanus – American bird's-foot trefoil
Additional Resources:

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

WA Flora Checklist: Acmispon americanus checklist entry.

E-Flora BC: Acmispon americanus atlas page.

CalPhotos: Acmispon americanus photos.

USDA Plants: Acmispon americanus information.

29 photographs:
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