Black Locust (False Acacia)

Basic Information
Tree ID: 
44
Family: 
Fabaceae
Genus and species: 
Robinia pseudoacacia
Description: 
Although it may not have any of the familiar green pods we've come to know from the food aisle, the black locust tree belongs to the pea family, Fabaceae. It's native to the southeastern United States and also the lower slopes of the Appalachian Mountains. A deciduous tree with short, irregular branches and feathery leaves, the black locust grows fast but is short-lived. Black locust trees can reach heights of 70 to 80 feet but are more often 30 to 50 feet tall. The black locust bears toxic pods that hang from its branches, but it also has white, fragrant flowers that bloom in late spring. These flowers produce a delicious and much sought-after honey that bees love. The black locust doesn't compete well with other trees and isn't a big fan of shade, but it's nevertheless a resilient species. It grows quickly, can survive drought and harsh winters, and creates new trees by sending up new sprouts from roots and stumps.
Surveyors: 
Mary Edgington and Hung Pham
Location
Area: 
Prospect and Sachem
Collected Data
Tree shape: 
Its crown has an irregular outline with general oval shape, while its branches grow mostly upright and do not droop.
Date of tree entry: 
02/05/2015
Height: 
17.64 m
Diameter at breast height: 
0.54 m

Bark
In its early stages, the bark of the black locust is smooth and green while mature trees have bark that is dark brown, deeply furrowed, and topped with ridges.
Twigs & branches
A remarkable feature of the black locust is its ability to grow new branches by sprouting new roots and shoots. The tree grows with a single leader and thorns can be found on the trunk or branches.
Foilage
In terms of foliage, it has an alternate leaf arrangement and odd pinnately compound structures. The blue to blue-greenish leaves have pinnate venation and grow no longer than two inches.
Reproductive Structures
The white, pleasantly flagrant flowers are found in drooping clusters 8 to 20 centimeters long in May and June. The flowers of the black locust are perfect, meaning they contain both male and female reproductive parts, stamens and carpels, respectively. A cultivar of the black locust tree, "purple robe," features flowers that range from lavender to a deep purple.
Fruit
The fruit of the black locust is classified as a legume. Pods are smooth, three to four inches long, and are either dark brown, black, or red. Pods typically contain four to eight seeds and ripen in late autumn. Pods hang on the branches of the black locust until early spring attracting birds and small mammals such as squirrels.
Seasons
  • As a deciduous tree, the black locust sheds all of its leaves in the winter.
  • In spring starting in May, black locust flowers are white.
  • In autumn, the white flowers turn a rich yellow.
  • As in the spring, the black locust flowers are a radiant white in the summer.
Research
Natural range of distribution: 
Habitat: 
Although it's native to the southeastern United States and on the lower slopes of the Appalachian Mountains, some black locust trees can also be found in the north along the slopes and forest edges of southern Illinois, Indiana, and Missouri. It flourishes in full sun, well-drained soils, and little competition. It's commonly sighted in areas that have been disturbed including roadsides, degraded woods, and old fields. It typically lives in cove or mesophytic forests.
Origin, history, and uses: 

Because of its need for minimal maintenance, the black locust is ideal for reclamation projects and roadside planting. Although a common misconception is that its wood is strong and durable (pioneers built ships and houses with black locust wood), its branches are actually brittle and damage easily in high winds.

The black locust has also been used for chemical pulping systems in the paper industry.

Its honey is not only cultivated by bees but also by humans commercially for trade and consumption. Its leaves are turned into livestock feed in Korea and Bulgaria and its flowers are edible.

The wood has a high heat content making it a good firewood. Young black locust wood is best for this use since burrowing by larvae in older trees causes the wood to split during burning, flinging burning coals several feet from the fire! 

References: 
Barrett, Robert P., Tesfai Mebrahtu, and James W. Hanover, “Black Locust: A Multi-Purpose Tree Species for Temperate Climates” in Advances in New Crops, ed. J. Janick and J.E. Simons (Portland, OR: Timberland Press, 1990), 278-283, https://www.hort.purdue.edu/newcrop/proceedings1990/v1-278.html#Wood.
 
“Black Locust (Robinia pseudoacacia),” National Park Service, last updated April 2, 2015, accessed April 14, 2015, http://www.nps.gov/whmi/learn/nature/black-locust.htm.
 
“Black Locust: Robinia pseudoacacia,” Fairfax County Public Schools, accessed April 14, 2015, http://www.fcps.edu/islandcreekes/ecology/black_locust.htm.
 
“Fact Sheet: Black Locust,” Plant Conservation Alliance’s Alien Plant Working Group, May 20, 2005, accessed April 14, 2015, http://www.nps.gov/plants/alien/fact/pdf/rops1.pdf.
 
Gilman, Edward F. and Dennis G. Watson, “Robinia pseudoacacia: Black Locust,” U.S. Forest Service, October 1994, accessed April 14, 2015, http://hort.ifas.ufl.edu/database/documents/pdf/tree_fact_sheets/robpsea.pdf.
Media and Arts
Informational video about the Black Locust and the honey it produces that bees covet, narrated by Steve Owens.
Poem, “The Sensitive Knife” by Gerald Stern
 
Every day the dark blue sky of brother Van Gogh
gets closer and closer,
and every day the blue gentians of brother Lawrence
darken my eyes.
it is blue wherever I go,
walking the towpath,
climbing the stone island,
swimming the river,
and everywhere I sit or kneel
the blue goes through me like a sensitive knife.
 
I am following my own conception now
and during the night I flap my two-foot wings
in the black locusts.
I move thoughtfully from branch to branch,
always loving the stiffness and shyness
of the old giants.
I think of my own legs as breaking off
or my wings coming loose in the wind
or my blossoms dropping onto the ground.
 
Across the river the sticks are coming to life
and Mithras and Moses and Jesus are swaying and bowing
in all directions.
I swim carefully through the blood
and land on my feet on the side of Carpenter’s Hill.
There on a flat rock
my father is placing the shank bone
and the roasted egg on a white napkin.
I climb over the rhododendrons and the dead trees to meet him. 
 
Spoken word poem, “It Never Lies” by Hung Pham
Imagine that all the oxygen I breathe, from the moment I begin to cry upon thundering into what is called life, the branches of one enormous tree exhaling with welcome. Breaths produced faster than mine, without expectation of compensation, breaths that give and keep giving as manifested memories of sunlight absorbed mornings ago—these breaths sit in between where the Black Locust and I trust each other.
 
It never lies to me. It never lies because it doesn’t know how like we know how to lie to each other. In this place, humming with an electricity that fosters a culture of hiding vulnerability as it pressures its worker bees to produce, to generate results, to forget how to breathe, I forget how to breathe.
 
It never lies to me. It never lies to me because when I found out mom got put into the hospital last week and the doctors didn’t know if she would make it, when I found out that dad who works as a day laborer couldn’t find work because of the California drought, when I found out that I had already been working 19 hours a week for all four years to send my paycheck home every week to my poor family but that they needed more to buy groceries now, I cried and forgot how to breathe. But what I could remember is that a sore heart and tired feet could be cured with short trips to see the Black Locust, with its naked sprawling branches from winter soon to blossom into the white flowers of spring, its petals chasing the light.
 
It never lies to me. The lampposts on Prospect illuminated the path to the Black Locust still tall, still strong, still with its brown, ridged bark in the 2:00 A.M. New Haven darkness. No matter how good the news or how sad the tragedies, the Black Locust remains the Black Locust remains tree #44 on the Yale Nature Walk remains what it promised to grow up to be. Unsure how to not be strong, my shaking arms wrapped around the furrowed, imperfect bark, learning themselves how to be imperfect. The Black Locust breathes faster than I do and with a larger, more altruistic purpose, without complexities, without pride, and with truth. As it sighs what I need to live, I exhale for it. This is how we talk.
 
It never lies to me. But I know, I know if I stand here for the rest of this lifetime, and the next, that I can’t lie to it either. Truth is inscribed within the breath, which it has reminded me how to make more of.
 
To the Black Locust, a resilient teacher that survives drought and harsh winters, and creates more of itself using itself to send up new sprouts: when I perish from the earth and return to it underneath the dirt upon which you triumph, I can only hope to make more of you as you have made more of me.
 
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