Black Locust

Black Locust
Basic Information
Tree ID: 
201
Family: 
Fabaceae
Genus and species: 
Robinia pseudoacacia
Description: 
This Black Locust Tree is found across Prospect Street from Sterling Chemistry Laboratory, and just up the hill from Ingalls Ice Rink. If you were a squirrel that lived in this tree, you would be able to see students walking to their laboratory classes in the morning and fans coming to cheer for the Yale hockey team in the evening. At lunchtime, you might even be able to smell the delicious scents of Thai and Mexican food from the food trucks by the intersection of Sachem and Prospect. At almost 70 feet tall, this particular Black Locust tree would give you an excellent bird's-eye view of campus. Despite its size, the Black Locust is actually a member of the pea family, Fabaceae. Black Locust trees produce fragrant flowers and pea pod-shaped fruits. While they are flexible with regards to soil type, and can grow in a variety of locations, Black Locust trees do require plentiful sunlight and open ground. Black Locust trees can be found throughout all of the United States except Alaska and Hawaii, as well as parts of Canada, Asia, Europe, and southern Africa. However, their normal range is limited to the southeastern United States. Black Locusts are valued for the honey produced from their flowers as well as its durable wood. However, this tree can become invasive due to its ability to produce large quantities of seeds and reproduce via root suckers.
Surveyors: 
Hannah Rubin and Usman Khalid
Location
Area: 
Prospect and Sachem
Collected Data
Tree shape: 
Irregular
Date of tree entry: 
02/04/2026
Height: 
20.82 m
Diameter at breast height: 
0.58 m

Bark
The bark appears thick, rugged, and strongly textured, with deep vertical grooves that form uneven ridges. These ridges do not form straight lines but instead twist and intersect, creating a rough, almost braided pattern across the surface. The bark has a slight variation in color, ranging from grayish to brown tones, with lighter areas appearing where the outer layers may have worn or split. The deep cracks and layered texture act as a protective outer surface that helps shield the tree from environmental stresses such as extreme temperatures, physical damage from wind or animals. The bark functions as a barrier that reduces water loss and limits infection, which helps the tree survive in harsh environments.
Twigs & branches
Black Locust twigs are either smooth or possess fine hairs. However, these twigs are also armed with pairs of spines at the base of each leaf. These spines, which are considered modified stipules, can also be found on the limbs and trunks of younger trees.
Foilage
The foliage of the black locust tree is made up of long, pinnately compound leaves, meaning each leaf is divided into many small, oval leaflets arranged along a central stem. These leaflets are typically smooth-edged and are dull green which contribute to a light, airy canopy that allows sunlight to pass through. The leaves are arranged alternately along the branches, which helps reduce overlap and improves light exposure for photosynthesis. This structure, along with the many small leaflets, allows the tree to efficiently capture sunlight while remaining flexible in wind and changing weather conditions. The leaves emerge later in the spring, remain green during the growing season, and then turn a yellow before falling in autumn.
Reproductive Structures
Black Locust trees flower between late April and early June depending on location. The flowers hang from the branches in long, axillary clusters 10 - 20 centimeters long. The flowers, white and fragrant, are about 2 centimeters long. The upper petal has a yellow spot on it. The fruit of the Black Locust is a dry, dark brown legume that resembles a pea pod. The fruits are 5 - 10 centimeters long and very thin. They split open to release their seeds.
Fruit
The fruit of the black locust tree develops from its flowers into legume pods which are pea-like pods that are typically flat, smooth, and about 2 to 4 inches long. They begin green and gradually turn dark brown as they mature. As the pods ripen, they dry out and become thin and somewhat papery, eventually splitting open to release their seeds. Each pod usually contains several small, hard seeds, often around four to eight, which are bean-like in appearance. The fruits often remain hanging on the branches well after ripening, sometimes lasting into the winter or early spring. This allows seeds to be released gradually as the pods dry and split open, with dispersal occurring through wind, gravity, and occasionally animals, which helps spread the seeds over a wider area and increases the chances of successful germination.
Seasons
  • Winter
  • Spring
  • Summer
  • Autumn
  • Spring
Research
Natural range of distribution: 
Habitat: 
The black locust tree is native to parts of the eastern United States, especially regions around the Appalachian Mountains, but it is widely found across North America. In its natural environment, it commonly grows in forested areas, particularly along slopes and stream edges, where the soil is moist but well-drained, meaning water can pass through easily without becoming waterlogged or overly saturated. This species grows best in direct sunlight as it is shade-intolerant. It is often found in disturbed areas, such as roadsides, old fields, or cleared land, where natural vegetation has been removed or disrupted and competition from other plants is low. Black Locusts can survive in nutrient-poor soils because it forms relationships with bacteria that fix nitrogen, allowing it to improve soil fertility and grow where other plants struggle. Its ability to tolerate harsh conditions, grow quickly, and spread through roots and seeds allows it to establish easily in open environments, especially after disturbances like erosion or land clearings.
Origin, history, and uses: 

The typical range of the Black Locust extends from the southern Appalachian mountains to the Ozark mountains of southern Missouri and parts of Arkansas and Oklahoma. However, it has also been planted in southern Canada, most of the United States, and abroad. The Black Locust is not a native species in Connecticut, and likely made its way here after being planted for specific purposes, such as erosion control or to use its wood.

Black Locust wood is considered to be one of the strongest woods in North America. It can be used for fence posts and ladder rungs, and it was also used for railroad ties before the days of modern wood preservation. Black Locust wood weighs 48.2 pounds per cubic foot, which is similar to the weight of oak wood.

The honey of Black Locust trees is prized for its fruity flavor and enticing fragrance. Unlike the honey commonly sold in stores, the color of Black Locust honey is clear white, pale yellow, or yellowish green. Black Locust bark was used by indigenous people as an emetic and to reduce toothache. The roots of a Black Locust tree contain nodules of nitrogen-fixing bacteria, so Black Locust trees were historically planted on old strip mines to restore the soil quality.

Several insects feed on the sap, leaves, and wood of the Black Locust. Some insects, such as Carpenterworms and Treehoppers, may not cause extensive harm to healthy trees. Others, such as Locust Leaf Miners and Bagworms, can stunt growth or cause loss of foliage. The Black Locust does not grow well in poorly drained soil or shady conditions, and its wood is susceptible to ice damage.

 
Phenology: 
The phenology of the black locust tree follows a seasonal pattern related to temperature and growing conditions. It is one of the earlier trees to leaf out in spring, typically producing leaves in late April to early May. Usually between May and June the tree flowers and produces clusters of white blossoms that are then pollinated. Following flowering, fruits develop through the summer and begin to ripen in early fall. By late fall, the pods dry and open, and seeds are gradually dispersed from around September through the winter months. Leaves begin turning yellow before dropping as the tree enters dormancy for the winter.
References: 

Concord, MA. (n.d.). Concordma.gov. https://concordma.gov/772/Black-Locust-Robinia-Pseudoacacia

Black Locust. (n.d.). Www.fs.usda.gov. https://www.fs.usda.gov/wildflowers/plant-of-the-week/Robinia-pseudoacac…

Black Locust : Indigenous Peoples’ Perspective Project : Programs | Events : Adkins Arboretum. (n.d.). Www.adkinsarboretum.org. https://www.adkinsarboretum.org/programs_events/ipp/black-locust.html

Burlew, R. (2012, April 28). Honey bee forage: black locust - Honey Bee Suite. Honey Bee Suite. https://www.honeybeesuite.com/black-locust-honey/

Intro to Trees of Indiana: Black Locust. (2022). Purdue University - College of Agriculture. https://ag.purdue.edu/news/department/fnr/2022/09/intro-to-trees-of-indi…

University of Connecticut Plant Database. (n.d.). Robinia pseudoacacia (Black Locust). https://plantdatabase.uconn.edu/detail.php?pid=434.

U.S. Department of Agriculture, Natural Resources Conservation Service. (2002). Black Locust (Robinia pseudoacacia) Plant Guide. https://plants.sc.egov.usda.gov/DocumentLibrary/plantguide/pdf/pg_ROPS.p…

Media and Arts

Couplet: A Wintery Silence (by Usman)

In winter’s still, the locust stands alone,

Its bark in twisted ridges, darkly grown.

Brown bark with braided seams hold tight,

Guarding life from cold and cutting night.

Its feathered leaves have long since turned and gone,

Fallen gold beneath the pale, low sun.

Yet slender pods still rattle in the air,

Dry, papery shells split open, seeds laid bare.

On windswept ground where light and silence meet,

It stands firm–weathered, enduring, and unyielding to the cold.

Sonnet: Spring (by Hannah)

Long after all the other trees have bloomed,

the Black Locust finally decides it’s spring!

Its fragrant blossoms clear away the gloom

that rainy days in May would surely bring.

In clusters, they pepper the branches white,

like stars to gazers on the grass below.

Honey bees, attracted to the sight,

sip nectar from the flowers, then they go.

Soon, I’ll pour sweet honey in a jar

and steep the petals into a sweet tea

I’ll can spring so it won’t ever be far,

so sunny days of hope will never leave.

And when the days are short and nights are dark,

I’ll have the taste of spring inside my heart!

 

Five Haikus: Summer (by Hannah)

summer vacation

time to photosynthesize

at last, some quiet

humans get bug bites

the black locust gets borers

they make twigs itchy

today it’s so hot!

gotta close those stomata

no water to lose

sunset, crickets chirp

drowsy evenings in August

softly rustling leaves

chatter, commotion

traffic scares away the birds

the students are back

 

Limerick: The Autumnal Echoes (by Usman)

There once stood a locust in fall,

With leaving yellow, then all

Drifting soft to the ground,

While its thin pods hung brown,

Rattling seeds as the wind gave a call.

Its bark, rough and ridged in the cold,

Held firm as the season grew old,

On open ground it stayed,

Where the sunlight still played,

Spreading roots through the fading gold.

Shrub Canopy Area: 
128.68sq.m.

Comments

Hannah Rubin on February 4, 2026:
Usman Khalid on April 22, 2026: