Virginia Tech Weed Identification Guide

Black Locust: Robinia pseudoacacia

Weed Description:  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.

Leaves:  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.

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.

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.

Identifying Characteristics:  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.