black locust

Fabales > Fabaceae > Robinia pseudoacacia L.
Synonym(s): false acacia, yellow locust

Black locust is a deciduous tree that, while native to parts of the United States, has spread to and become invasive in other parts of the country. Trees grow from 40-100 ft. (12-30 m) in height. Trees grow upright in forests, but develop an open growth form in more open areas. Leaves are pinnately compound with 7-21 small, round leaflets per leaf. Leaflets are 1.5 in. (4 cm) long. A pair of long, stipular spines is found at the base of most leaves. Flowering occurs in the spring, when flowers develop in 8 in. (20.3 cm) long clusters. The showy, fragrant, white to yellow flowers give way to a smooth, thin seed pod that is 2 to 4 in. (5.1-10.2 cm) in length. The bark of black locust is light brown, rough, and becomes very furrowed with age. Black locust is native to the Southern Appalachians, the Ozarks, and other portions of the Midsouth, but is considered an invasive species in the prairie and savanna regions of the Midwest where it can dominate and shade those open habitats.


Identification, Biology, Control and Management Resources


Selected Images from Invasive.org

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Diagram or Graphic; 1. Branchlet with flowering and leafy shoots. Pea-flower shaped (papilionaceous) flowers open in pendulous terminal racemes. Odd-pinnate compound leaves with short petioluled leaflets. - 2. Shoot with ripe pods (f) and pendulous leaflets (B) during night. Fruits are many-seeded flat pods. - 3. Ripe seed as seen from two aspects. - 4. Seedling with cotyledons (c) and first ordinary leaves. - 5. Winter-branchlet - terminal bud is missing. Buds are small, naked, hidden inside the leaf scars and typically located between two modified spiny stipules. After Hempel & Wilhelm, 1889. Photos and explanations from the book: Zelimir Borzan. "Tree and Shrub Names in Latin, Croatian, English, and German, with synonyms", University of Zagreb, 2001.
Zelimir Borzan, University of Zagreb, Bugwood.org
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Foliage;
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Foliage;
Paul Wray, Iowa State University, Bugwood.org
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Foliage;
James H. Miller, USDA Forest Service, Bugwood.org
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Foliage;
James H. Miller, USDA Forest Service, Bugwood.org
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Bark;
Paul Wray, Iowa State University, Bugwood.org
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Feature(s); Stipular Spines
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Flower(s);
Paul Wray, Iowa State University, Bugwood.org
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Flower(s);
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Flower(s);
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Flower(s);
Bill Cook, Michigan State University, Bugwood.org
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Flower(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Flower(s);
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Flower(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Fruit(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Fruit(s);
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Fruit(s); fruits remaining in spring from previous year
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Fruit(s);
Paul Wray, Iowa State University, Bugwood.org
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Fruit(s);
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Fruit(s); fruit and seeds
Paul Wray, Iowa State University, Bugwood.org
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Feature(s); Clonal Growth
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Tree(s);
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Tree(s); in flower
Jan Samanek, State Phytosanitary Administration, Bugwood.org
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Tree(s);
Chris Evans, River to River CWMA, Bugwood.org
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Seedling(s);
Brian Lockhart, USDA Forest Service, Bugwood.org
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Sapling(s); Yound sapling growing within a 50 year old pine stand. Poland
Gil Wojciech, Polish Forest Research Institute, Bugwood.org
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Seed(s);
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
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Diagram or Graphic; Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 2: 375.
USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org
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Invasive Reference(s):

Check Invasive.org for most current lists.
  • California - Invasive Plant Inventory
  • Massachusetts - Noxious Weed Law
  • Rhode Island - Noxious Weed Law
  • Mid-Atlantic - EPPC List
  • Invasive Plants: Guide to Identification and the Impacts and Control of Common North American Species
  • Invasive Plants of the Upper Midwest
  • Invasive Plant Atlas of New England


External Links


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