Honey Locust

Basic Information
Tree ID: 
Genus and species: 
The Gleditsia triacanthos, or honey locust as its commonly called, is a decidious tree native to the central United States. It blooms relatively late in the spring and produces yellow leaves in autumn. The tree gets its name from the sweet, sticky pulp it produces. Alternatively, the tree is known as the "thorny" locust due to the spines or thorns that it bears on wood of its main trunk or the base of its branches. The honey locust has also historically been used for a wide variety of medicinal practices, particularly in Native American culture. Today, the honey locust has a number of applications: its fruit is used in agriculture to feed livestock; its dense wood is used to make furniture and fences; and its unique compounds may have medicinal uses for treating diseases like rheumatoid arthritis and cancer. This honey locust is located at the corner of Yale University Science Hill parking lot near the intersection of Whitney Avenue and Bishop Street.
Kristina Kim, Nathan Adams and Hannah Friedman
Collected Data
Tree shape: 
Oval; Round; Spreading
Date of tree entry: 
6.18 m
Diameter at breast height: 
0.15 m

The bark of the honey locust is initially, gray-brown to red-brown to bronze in color, and smooth with many horizontal lenticels (raised pores used for gas exchange) that later turn into long, narrow, curling plates. In addition, the honey locust's bark often displays clusters of large, branched thorns on its trunk. Its wood is strong, coarse grained and moderately durable, which is why it is a material commonly used fence posts, railroad ties, furniture, interior woodwork and fuelwood.
Twigs & branches
The twigs of the honey locust may be either stout or slender and they can prominantly zig-zag. The color of these twigs are red-brown to light greenish-brown in color. The twigs and branches have numerous lenticels and they often feature branched thorns. Older twigs and branches can be found with single or three-branched or more thorns that can be between one and four inches long. The lateral buds found on the twigs are very small and sunken.
The honey locust has leaves that are compound (pinnately) or doubly compound (bipinnately) leaves that alternate. The pinnately compound leaves are 5 to 8 inches long with 15 to 30 leaflets. The bipinnately compound leaves have 4 to 7 minor leaflets which are 0.5 inches to 1.5 inches long. The shape of the leaves are ovate/elliptical. The leaves are a dark green color in the spring, but in the fall, the leaves of this deciduous tree become a golden yellow color.
Reproductive Structures
The honey locust in polygamo-dioecious, which means that the species has unisexual flowers with male (staminate) and female (pistillate) flowers on different trees, but also some perfect flowers (both male and female parts) on each tree. The flowers are small and they are displayed on 2 to 3 inch long narrow, hanging clusters. The flowers are greenish yellow in color, but they are not showy. Although the flowers are not showy, they are very fragrant. The flowers are pollinated by insects. The flowers tend to appear in the late spring and early summer. The male (staminate) flowers are found in elongated drooping clusters (about 2-3 inches long) on golden hairy branches coming out from the leaf forks. The female (pistillate) and bisexual flowers occur singly or in few-flowered clusters (3-4 inches long) on golden hairy, drooping branches in the leaf forks. As mentioned above, the flowers appear to be an inconspicuous, greenish or creamy-yellow color. The sepals of the flowers are about 3-4 mm long and the petals of the flowers are about 3-6 mm long. The male flowers have short stalks or no stalks and they have 5-7 hairy (pubescent) stamens. In contrast, the female and perfect flowers have longer stalks and have a hairy (pubescent) ovary. The ovary has a broad style and a two-lobed stigma on top of it.
The fruit of the honey locust is a compressed, flattened and leathery or slighlty hairy pod. The color of these pods ranges from green to red- or purple-brown and from dark brown to black. The shape of these pods is pendulant, curved and twisted. The pods range in size from about 6-18 inches long and about 1-1.5 inches wide. The pods are thick-walled and they taper at both ends. The pods of the honey locust are often found in clusters of two or three. The honey locust usualy produces a large fruit crop only every 2-3 years with the southern trees often having larger crops than the northern trees. Once formed, these pods can remain on the tree from September to February. After the pods fall to the ground, they remain unopened and do not open themselves to release their seeds. Instead, the honey locust relies on various species of wildlife and livestock to eat the pods and spread their seeds. These animals can include horses, cattle, rabbits, foxes and crows. Each pod has about 6-20 seeds and a yellow, brown or light green, sugary, sweet pulp, which makes sense given that they rely on animals for dispersal. The seeds are about 1/3 inches long, hard, flat, oval-shaped, shiny and dark brown. The thick seed coat requires a pass through an animal's digestive system in order to become permeable and allow for seed germination.
  • Winter (Photo by Kristina Kim)
  • Summer
  • Honey Locust in Fall (Photo by Famartin)
Natural range of distribution: 
The honey locust tree is found in central North America, usually in moist soil near river beds and in open plain regions or in mixed forests. It is quite adaptable and can survive in a variety of conditions such as drier areas and suburban and urban environments provided it receives enough sunlight. For this reason, it is often used as an ornamental tree in parks and in urban areas. It fares less well in densely wooded areas as it is intolerant of shade.
Origin, history, and uses: 

The honey locust originates from the central United States, ranging from central Pennsylvania in the east to Nebraska in the west and Southern Minnesota in the north to Louisiana in the south. They are most concentrated, however, in the stream valleys and wetlands of southern Illinois and Indiana.

Historically, this tree has been a source of good timber for human use. Gleditsia triacanthos features strong, dense wood that is resistant to rapid decomposition. Its durable properties have made it an attractive option for human construction. The Cherokees in Tennessee first used this wood to construct their bows. In modern times, this wood remains a solid option for small wooden construction projects such as fencing, crating, or furniture. Due to its sparse distribution though, the honey locust has not been exploited as a lumber source for bulk industry, but rather is used locally when available.

Additionally, the honey locust has a number of applications in agriculture. The nutrient-rich fruit of this plant (large seed pods) are edible by a number of species. In the wild, rabbit, deer, squirrels and a myriad of small birds (among other species) all eat the fruit produced by the honey locust. Following their lead, humans have implemented the use of this plant in agriculture to feed livestock, such as cattle and hogs. The pods produced by the honey locust provide a good option since they are especially rich in carbohydrates and proteins, possess a sweet flavor, and are readily available in certain regions. Flowers of this plant are also a target of many insect species and are important source of food for bees. Finally, Gleditsia triacanthos are planted in areas to prevent erosion and provide windbreaks.

The honey locust has a number of properties that provide potential avenues of use in scientific realms. For instance, the honey locust has been the subject of research into a potential source for biofuels. Extracts from the plant have also been found to contain a number of useful isolates. Seed extracts have yielded a Trypsin Inhibitor (which has potential clinical applications in a variety of biological investigations) as well as a number of antioxidant and phenolic compounds that could be used as a cheap alternative in food packaging. Further, other extracts of this plant have found compounds that are useful in a number of other areas like treating rheumatoid arthritis, anti-mutagenic and anti-cancer treatments, and inducing cytotoxic activity in a number of distinct cell lines. 

Phenology – study of how the biological world times natural events – is affected by three main non-biological factors: sunlight, temperature and precipitation. The honey locust flowers when its leaves are almost fully grown, which occurs between mid-late May (southern parts of its distributional range) to mid-June (northern region). The tree's seeds ripen between September to October and after ripening, they usually fall off of the tree. However, these seeds sometimes stay on the tree through the winter months to around February. The seed bearing age of honey locust trees is ten years old. The seed bearing frequency of the species is about every year with abundant crops occuring every year or two. The seeds are distributed through animals such as cows, birds and other small mammals. Although the seedlings of the honey locust are able to growth in shady environments with clay soils, the honey locust tree generally prefers full sun, which means it should receive at least six hours of direct, unfiltered sunlight daily for ideal growing conditions. The honey locust is able to grow in a variety of soils, temperatures and moisture conditions. The tree has moderate tolerance for flooding and drought. The honey locust cannot survive exposure to temperatures below -33 degrees Fahrenheit. Finally, the precipitation range for the honey locust's growth is about 35 inches per year.
  1. Arbor Day Foundation. (n.d.). Thornless Honeylocust: Gleditsia triacanthos form inermis. Retrieved April 26, 2016, from https://www.arborday.org/trees/treeguide/TreeDetail.cfm?itemID=852 
  2. Blair, R. M. (n.d.). Honeylocust. Retrieved April 26, 2016, from http://www.na.fs.fed.us/spfo/pubs/silvics_manual/volume_2/gleditsia/triacanthos.htm 
  3. Butko, A. (n.d.). Gleditsia triacanthos in Donetsk 1 [Digital image]. Retrieved April 27, 2016, from https://commons.wikimedia.org/wiki/File:Gleditsia_triacanthos_in_Donetsk…
  4. Cerqueira, M. A., Souza, B. W., Martins, J. T., Teixeira, J. A., & Vicente, A. A. (2010). Seed extracts of Gleditsia triacanthos: Functional properties evaluation and incorporation into galactomannan films. Food research international, 43(8), 2031-2038.
  5.  Famartin. (2014, October 11). 2014-10-11 12 49 16 Honey Locust foliage during autumn in Elko, Nevada [Digital image]. Retrieved April 27, 2016, from https://commons.wikimedia.org/wiki/File:2014-10-11_12_49_16_Honey_Locust…
  6.  Famartin. (2014, October 30). 2014-10-30 10 51 02 Honey Locust foliage during autumn on Farrell Avenue in Ewing, New Jersey [Digital image]. Retrieved April 28, 2016, from https://commons.wikimedia.org/wiki/File:2014-10-30_10_51_02_Honey_Locust…
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  10. Kevmin. (n.d.). Gleditsia triacanthos Maryhill Museum [A single legume from a medium (~12-15 foot tall) honey locust (Gleditsia triacanthos) tree planted on the grounds of the Mary Hill Museum, Washington, USA.]. Retrieved April 27, 2016, from https://commons.wikimedia.org/wiki/File:Gleditsia_triacanthos_Maryhill_M…
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  17. Shadow, R. A. (n.d.). HONEY LOCUST Gleditisia triacanthos L. Plant Fact Sheet [PDF]. Nacogdoches, TX: USDA/NRCS East Texas Plant Materials Center. Retrieved April 27, 2016, from http://plants.usda.gov/factsheet/pdf/fs_gltr.pdf. 
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Media and Arts

Oh Honey [Locust], How You’ve Grown!

by Nathan Adams and Hannah Friedman

There in your honey pod you rest

Lying snug among your friends.

Safely in your mother’s nest,

You hope it never ends.

New in life, you are green

(and I mean in more ways than one).

The world remains still unseen,

but bright beneath the summer sun.

Yet time goes by and Fall draws near

Your pod begins to dry.

Leaves rustle in the morning clear –

The time has come to fly!

Your pod it drops from quite a height

And breaks upon the ground

Your friends are strewn all out of sight

Your seedling cries make not a sound.

You burrow deep into the earth

As winter’s cold begins to bite

Soil covers your seedy girth

And soon you can’t see light.

The months go past

A blur of cold, lonely fear.

Yet you know the freeze won’t last

For Spring must come each year.

And soon it brings the sun’s warm rays;

The ground gets soft and wet.

With it comes the longer days,

A new spirit, a fresh mindset.

You stretch your neck up through the soil

To let your joy be known.

Leave behind your hardship and toil.

Oh Honey [Locust], how you’ve grown!

Once sprouted it quickly climbs

Beneath the sun it casually mimes

A man reaching, arms outstretched

Snatching all sunlight it can catch

It’s thorns burst from beneath the bark

Extending out in a graceful arc

Soon its leaves change from green to gold

No less splendid in the cold

Branching from the earth where the seed was sown

Oh Honey (Locust), how you’ve grown!