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Weed Identification

black locust



Scientific Name

Robinia pseudoacacia

Other Common Names:

yellow locust
false acacia

Synonyms (former Scientific Names):

Robinia pseudoacacia var. rectissima
Robinia pseudoacacia f. inermis
Robinia pseudoacacia var. pyramidalis


Arranged alternately along the stem, approximately 8 to 12 inches in length. Leaves are divided into two rows of 7 to 19 leaflets that are elliptic to oval shaped in outline and range from 3/4 to 2 inches in length and 1/2 to 3/4 inch in width. Young seedlings have leaflets that are often densely covered with short hairs.

Identifying Characteristics

A tree that may reach as much as 100 feet in height when mature, but the seedlings of these trees often occur as weeds of landscapes, pastures, hay fields, gardens, and roadsides. The alternately arranged leaves that consist of many leaflets, stipules that develop into spines, and underground stems that can produce new plants are all characteristics that help in the identification of black locust. Several other locust species occur and are primarily differentiated from black locust by their flower color and type of fruit.

Flower Seed Head

Stems: Seedlings have stipules that develop at the base of the leaf petioles and the stems. These stipules develop into woody spines that may reach as much as 1 inch in length with age. Roots: Underground stems that are capable of regenerating new plants and a fibrous root system. Flowers: A drooping raceme, 4 to 8 inches in length, containing many fragrant flowers. Individual flowers are white and yellow in color.

Seed Fruit

A pod (legume) that is twisted, 12 to 18 inches in length and 1/2 to 3/4 inches in width. A narrow wing occurs along the upper surface of the legume.

Where Found

Black locust s native range follows the Appalachian Mountains from Pennsylvania to Alabama, and a secondary population exists primarily in the Ozark Mountains. Black locust is adapted to a wide variety of soil types, but grows best on sites that are deep, well drained, and derived from limestone. This tree tolerates a pH range of 4.6 to 8.2. It is commonly found on south and west slopes in West Virginia

Growth Habit

woody bush or tree

Thorns or Spines


Approximate Flower Diameter


Dominant Flower Color


Flower Symmetry

not symmetrical

Leaf Hairs

no hairs

Leaf Shape


Leaf Margin


Leaf Structure


Leaf Stalk

longer than leaf

Stem Hairs

has hairs

Stem Cross Section

round or oval

Milky Sap

not present

Life Cycle



not present

Plant Type