E-Flora BC: Electronic Atlas of the Flora of British Columbia

Robinia pseudoacacia L.
black locust
Fabaceae (Pea family)

Introduction to Vascular Plants

© Brian Klinkenberg  Email the photographer   (Photo ID #21620)

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Distribution of Robinia pseudoacacia
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Black locust is deciduous weedy tree species in the Pea Family (Fabacaea). It is native to the southeastern United States but has been introduced across the US and parts of Canada where it has been used both ornamentally and in land reclamation (USDA 2010). In BC, it has escaped and naturalized in the southern part of the province in disturbed areas and forest edges. It is a tall (to 25 m), nearly glabrous, deciduous tree that reaches heights of 80 ft. It has dark-brown, deeply furrowed bark and prickly branches with alternate, large, and pinnate leaves that have (7) 11 to 21 leaflets. The white flowers are very fragrant, producing drooping, smooth, shiny pea pods that contain 4 to 8 seeds and remain on the branches in winter. It reproduces from seeds, suckers, and stump sprouts and can form thickets (Global Invasive Species Database 2010). Across its range, it is particularly invasive in "dry and sand prairies and oak savannas" (Global Invasive Species Database 2010). View more photos of this species.

Species Information

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Fast-growing, spiny tree with thick, furrowed bark, to 25 m tall, often spreading by underground suckers.
Alternate, deciduous, stalked, pinnately compound; leaflets 11 to 21, paired, lanceolate to elliptic-oval, 2-4 cm long, bright green on the upper surface, pale beneath; stipules modified into spines.
Inflorescence a stalked, axillary, drooping raceme 10-14 cm long, of 30 to 70 fragrant, pea-like flowers; corollas white, 14-20 mm long, the banner yellow-blotched at the base; calyces bell-shaped, 5-6 mm long, densely hairy.
Pods, oblong, flattened, 6-12 cm long, drooping, glabrous, becoming papery and darkening with age, persistent through winter.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Fruit/Seed characteristics:
Colour: Black
Present from Spring to Summer
Source:  The USDA

Habitat / Range

Mesic disturbed areas and forest edges; rare horticultural escape in SW and SC BC; native to E U.S.

Source: The Illustrated Flora of British Columbia


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Robinia pseudoacacia (Mirb.) Rehder
Robinia pseudoacacia var. pyramidalis Pepin
Robinia pseudoacacia var. rectissima (L.) Raber

Taxonomic and Nomenclatural Links

Additional Photo Sources

Species References

Bailey, L. H. 1949. Manual of Cultivated Plants Most Commonly Grown in the Continental United States and Canada. MacMillan Publishing Co. Inc., New York. Revised Edition.

Global Invasive Species Database. 2010. Robinia pseudoacacia. Compiled by the National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG).

Stone, Katharine R. 2009. Robinia pseudoacacia. In: Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Available Online.

USDA. 2010. Plant profile for Robinia pseudoacacia. USDA Plants Database. United States Department of Agriculture. Available Online.

General References