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Montana Field Guide

Montana Field Guides

Black Locust - Robinia pseudoacacia
Other Names:  False Acacia

Non-native Species

Global Rank: G5
State Rank: SNA
C-value: 1

Agency Status


External Links

General Description
Trees to 20 m with furrowed bark. Herbage glabrate to puberulent. Stems sometimes with nodal spines. Leaves petiolate, odd-pinnate with 9 to 17 ovate to narrowly elliptic leaflets 2–6 cm long with pubescent petiolules; stipules linear, early-deciduous. Inflorescence axillary, pendent, densely-flowered raceme 5–20 cm long. Flowers papilionaceous, white; calyx pubescent; sepals deltoid,1–3 mm long, lower 2 larger; banner 14–19 mm long with a yellow center, ca. as long as the wings and keel; stamens 9 united, 1 separate. Fruit a linear, glabrous legume flattened parallel to the sutures, 4–10 cm long, slightly indented between the seeds (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Range Comments
Collected in Lake and Missoula counties. Introduced from eastern North America to much of the U.S. and Europe (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 9

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Relative Density



(Observations spanning multiple months or years are excluded from time charts)


The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus centralis, Bombus fervidus, Bombus pensylvanicus, and Bombus griseocollis (Thorp et al. 1983, Colla and Dumesh 2010).


  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
    • Little, E.L., Jr. 1979. Checklist of United States trees (native and naturalized). Agriculture Handbook No. 541. U.S. Forest Service, Washington, D.C. 375 pp.
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Citation for data on this website:
Black Locust — Robinia pseudoacacia.  Montana Field Guide.  .  Retrieved on , from