Black Locust

(Robinia pseudoacacia)

Interesting Information About Plant:

The Black Locust is native to the Eastern United States. It was brought to the Western United States (California) by gold miners, who grew the plant for mining timbers. Once in California, it was planted because the wood made excellent railroad timbers. Black Locust was later brought overseas to France in the 1600’s. In France the wood was used for shipbuilding, the flowers were used in cooking, and the fruit was used as a coffee substitute.

Black Locust is a very hardy and competitive plant. It adapts well to a variety of soils and can survive droughts and harsh winters. It reproduces by root suckering and stump sprouting to form clones, which are all connected by a fibrous root system. Because of this, Black Locust can be hard to control. Even though it grows very fast (it can reach heights of 50-100 feet), it rarely lives to be 100 years old.

The Black Locust inner bark, roots, and twigs are poisonous to livestock, especially horses, and can be fatal. The seed is poisonous to humans.

Today the Black Locust is primarily used to stop soil erosion and it is also important in bee keeping. It is often planted near hives so the bees can get nectar from flowers and make honey. The wood is also important, and it is used in shipbuilding (yachts), furniture, and fence posts.

As mentioned earlier, the Black Locust is a very hardy plant, but it is susceptible to damage from two native insects: the locust borer and the locust leaf miner. The Locust Borer only attacks the Black Locust. It tunnels into the trees trunk and branches and weakens the tree, making it susceptible to wind damage.

Common Name: Black Locust

Scientific Name: Robinia pseudoacacia

Family Name (Scientific and Common): Fabaceae (Pea Family)  

Continent of Origin: Southeastern United States

Most Distinguishing Morphological Features of This Plant: The leaves of the Black Locust are composed of 7-20 leaflets, which are oval and rounded and slightly pointed at the ends. The leaflets themselves are not that big (1/2-2 inches long). At nighttime, the leaflets fold up and droop. Because of all the leaflets, the Black Locust has a feathery appearance.

Plant Growth Habit: Large Tree

Height at Maturity:  More than 10 Feet

Life Span: Perennial

Seasonal Habit: Deciduous Perennial

Growth Habitat:  Full Sun

Manner of Culture:  Native Species

Thorns on Younger Stem?:   Yes

Cross Section of Younger Stem: Roundish

Stem (or Trunk) Diameter:  More Than The Diameter of a Coffee-Mug 

Produces Brownish Bark?:   Yes 

Bark Peeling in Many Areas?:   No

Characteristics of Mature (Brownish) Bark: Lines Go Up-Down

Type of Leaf: Flat, Thin Leaf

Length of Leaf (or Leaflet):  Less than Length of a Credit Card

Leaf Complexity:  Pinnately Compound

Shape of Leaf:  Pinnately-Lobed

Edge of Leaf?:    Smooth

Leaf Arrangement:  Alternate

Leaf has Petiole?:  Yes

Patterns of Main-Veins: Pinnate

Leaf Hairiness:  No Hairs

Color of Foliage in Summer:  Green

Change in Color of Foliage in October:  No Change

Flowering Season:  Spring

Flowers:   in Loose Group 

Type of Flower: Colorful Flower

Color of Flower:  White 

Shape of Individual Flower: Bilaterally Symmetrical

Size of Individual Flower: Between a Quarter and the Length of a Credit Card

Sexuality:  Hermaphroditic Flower

Size of Fruit:  Between a Quarter and the Length of a Credit Card

Fruit Fleshiness at Maturity?:   Dry

Shape of Fruit: Long Pod

Color of Fruit at Maturity:  Brown or Dry

Fruit Desirable to Birds or Squirrels?:      Yes   

Unique Morphological Features of Plant: The numerous leaflets and their small size gives the tree a feathery appearance.

Is the Plant Poisonous: Part of Plant

Pesty Plant (weedy, hard to control)?:    Yes

Common Name(s): Common Locust, Yellow or White Locust

Louisville Plants That Are Most Easily Confused With This One: None—no other plants in Louisville are commonly confused with it

Page prepared by: 

Ashlee Austin

 November 2005