Page authors: Don Knoke, David Giblin
Robinia pseudoacacia
black locust

Distribution: Occurring on both sides of the Cascades crest in Washington; introduced from Alaska to California, east to the Rocky Mountains, native from the Great Plains to eastern North America.

Habitat: Stream and river banks, forest edge, wastelots, abandoned homesteads, and disturbed areas.

Flowers: May-June

Origin: Introduced from central and eastern North America

Growth Duration: Perennial

Conservation Status: Not of concern


Well-armed tree to 25 m. tall, the bark thick.


Leaves odd-pinnate, leaflets 11-21, lanceolate to elliptic-oval, 2-4 cm. long, bright green on the upper surface, paler beneath; stipules often modified into thorns.


Inflorescence of large, pendant, axillary racemes 10-14 cm. long and 30- to 70-flowered; flowers fragrant, white, 14-20 mm. long; calyx broadly bell-shaped, thickly pubescent, 5-6 mm. long, the 5 teeth very broad; corolla pea-like, the banner reflexed, with a yellow blotch at the base.


Pod flattened, 6-10 cm. long, 2-valved.

Accepted Name:
Robinia pseudoacacia L.
Publication: Sp. Pl. 2: 722. 1753.

Synonyms & Misapplications:
Robinia pseudo-acacia L., orthographic variant [HC]
Robinia pseudoacacia L. var. pyramidalis (P├ępin) C.K. Schneid.
Robinia pseudoacacia L. var. rectissima (L.) Raber
Additional Resources:

PNW Herbaria: Specimen records of Robinia pseudoacacia in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Robinia pseudoacacia checklist entry.

OregonFlora: Robinia pseudoacacia information.

E-Flora BC: Robinia pseudoacacia atlas page.

CalPhotos: Robinia pseudoacacia photos.

USDA Plants: Robinia pseudoacacia information.

44 photographs:
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