black locust

(Robinia pseudoacacia)

Conservation Status
black locust
Photo by Randy
  IUCN Red List

LC - Least Concern


N5 - Secure

SNA - Not applicable


not listed

Weed Status

Restricted Noxious Weed

Black locust is listed as an invasive terrestrial plant by the Minnesota Department of Natural Resources.

Wetland Indicator Status
  Great Plains

UPL - Obligate upland


FACU - Facultative upland

  Northcentral & Northeast

FACU - Facultative upland


Black locust is a medium-sized, fast-growing, short-lived, deciduous tree rising on a single trunk from a shallow, wide-spreading root system. It can be 30 to 100 in height and 12 to 40in diameter at breast height, though in Minnesota mature trees are usually no more than 60 tall and 6in diameter. It reproduces by seed and spreads aggressively by suckers. It often forms thickets.

The trunk is often crooked. The crown is narrow, open, and irregular. The branches are spreading to ascending, short, crooked, and brittle.

The bark on young trees is smooth and gray or brown. On mature trees the bark is gray or brown, thick, and separated into long, forking ridges and deep furrows.

First-year twigs are light green and slightly hairy. Second-year twigs are slender, brittle, brown or reddish-brown, and hairless, with scattered lenticels. There is a pair of spines at each node. The spines are broad-based, sharp, and ½ to 1 long. The leaf scars are triangular to 3-lobed. They have 3 bundle scars and often 3 irregular cracks.

There are no terminal buds. Lateral buds are tiny, hairy, and not easy to see. Clusters of 3 or more buds are concealed in the leaf scar beneath the base of the leaf.

The leaves are alternate, deciduous, and 3 to 8 long. They are pinnately divided into 7 to 19 leaflets. They are on to 1 long, sparsely to moderately hairy leaf stalks.

The leaflets are elliptical to oblong, ¾to 2 long, and to 13 16 wide. They are rounded at the base and rounded or blunt at the tip. The leaf tip is occasionally slightly notched and has a short, sharp, abrupt point. The upper surface is dark green, not shiny. The lower surface is pale green and is usually sparsely covered with short, appressed hairs. The margins are untoothed.

The inflorescence is a drooping, unbranched cluster (raceme) rising from upper leaf axils of current-year branches. Each raceme is 2 to 5 long and has 8 to 30 flowers.

Individual flowers are ¾ to 1 long and white. They are on on 3 16 to long, hairy stalks. The 5 green, finely hairy sepals are fused for most of their length into a bell-shaped, to 5 16 long tube (calyx), then separated into 5 shallow lobes.

The 5 petals are butterfly-like, as is typical of plants in the Pea family. They are organized into a banner petal, two wing petals, and two fused keel petals. The banner is upright and bent backward along both sides. The wings are straight and project forward. The keel is curved upward. There are 10 stamens and a single style. The flowers are strongly scented.

The fruit is a drooping, narrowly oblong, flat, hairless seedpod containing 2 to 10 seeds. It is 13 16 to 4 long, to 1 wide. It is green at first, turning brown as it ripens. The pod matures early August to early September.




30 to 60




Records are not kept for nonnative species.


Flower Color




Similar Species


Moist. Forest borders and openings. Shade intolerant.




Mid-May to mid-July


Pests and Diseases






Distribution Map



2, 3, 4, 5, 7, 8, 22, 24, 28, 29, 30.




Native to Pennsylvania, West Virginia, Illinois, Missouri, Oklahoma, Georgia, and Kentucky. Introduced and naturalized in Minnesota.





  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Rosanae  


Fabales (legumes, milkworts, and allies)  


Fabaceae (legumes)  
  Subfamily Faboideae  
  Tribe Robinieae  
  Genus Robinia (locust trees)  



Robinia pseudo-acacia

Robinia pseudoacacia f. inermis

Robinia pseudoacacia var. pyramidalis

Robinia pseudoacacia var. rectissima


Common Names


black locust

false acacia

yellow locust















The upper angle where a branch, stem, leaf stalk, or vein diverges.



The group of outer floral leaves (sepals) below the petals, occasionally forming a tube.



A corky, round or stripe-like, usually raised, pore-like opening in bark that allows for gas exchange.



On a compound leaf, having the leaflets arranged on opposite sides of a common stalk. On a bryophyte, having branches evenly arranged on opposite sides of a stem.



An unbranched, elongated inflorescence with stalked flowers. The flowers mature from the bottom up.



An outer floral leaf, usually green but sometimes colored, at the base of a flower.



A basal shoot rising from the roots or from a bud at the base of a shrub or tree.

Visitor Photos

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    black locust   black locust  
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    black locust   black locust  


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  Robinia pseudoacacia
Blake C. Willson
  Robinia pseudoacacia  

Black Locust

  Black Locust
  Black Locust  

Copyright DianesDigitals

  Robinia pseudoacacia - Black Locust
Virens (Latin for greening)
  Robinia pseudoacacia - Black Locust  

Leguminosae - Pea Family (alt. Fabaceae - Bean Family)

Robinia pseudoacacia - Black locust poses a serious threat to native vegetation ecosystems outside of its historic North American range.

Southeastern United States and other separate outliers.

Source: Plant Conservation Alliance, Alien Plant Working Group

  Black Locust (Robinia pseudoacacia)
Andree Reno Sanborn
  Black Locust (Robinia pseudoacacia)  

Prohibited in Massachusetts and Connecticut.

  Black locust (Robinia pseudoacacia)
Jim Hamilton

Uploaded on Jun 18, 2008

Species information for black locust.




Visitor Videos

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Other Videos
  The Black Locust

Uploaded on Jul 9, 2011

The Black Locust (Robinia pseudoacacia) ranks among the 40 worst invasive tree species in the world. In 1601 its first seeds were sent from the Americas to France. Since then it has made its way into gardens in Africa, Asia and Australia. Unfortunately it also spreads readily into the wild where it overgrows all native vegetation.

Watch this related video on mail order invasions:

  Comparing toxic Black Locust pod and an edible Honey Locust pod

Uploaded on Nov 21, 2011

Many people on YouTube, including some nursery owners (who should know better!), cannot tell the difference between a toxic Black Locust pod and an edible Honey Locust pod.

Just a quick look, in the garden, today, at the difference between Black Locust pods and Honey Locust pods. You can see that the Black Locust pods are only tiny in comparison to the giant (brown-coloured) Honey Locust pods. There is also a leaf difference, too. The Gleditsias have smaller leaves and the Robineas have larger leaves.

This video is for entertainment purposes only. Always seek the advice of botanists, medical and wild food experts before ever ingesting any wild or foraged foods.

  Trees with Don Leopold - black locust

Uploaded on Oct 21, 2011

No description available.

  Black Locust identification video

Published on Aug 6, 2012

Black Locust identification (Robinia Pseudoacacia). It is the tree for fence post because the wood last forever.

  Black Locust Tree (rev 5-11)

Uploaded on May 29, 2011

No description available.




Visitor Sightings

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Location: Albert Lea, MN

Black locust in Albert Lea

black locust  






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