Common Name: Black Locust, Yellow Locust, Locust Tree, Robinia, False Acacia – The name locust tree is attributed to the religious sects that immigrated to North America in the 17th Century. According to the Bible, John the Baptist ate locusts and wild honey (Matthew 3:4). The “locusts” are believed to have been pods of the Carob tree, a member of the legume or pea family indigenous to the Middle East. Since the Locust tree resembles the Carob tree, its name reflects the biblical reference. The Carob tree is also called Saint John’s Bread, and, ironically, Locust tree.
Scientific Name: Robinia pseudoacacia – The genus is named for Jean Robin, the herbalist of the King Henri IV of France who introduced the tree to the Jardin des Plantes in Paris. The species name means “false acacia” which also reflects the similarity in the appearance with the Acacia tree, also a member of the legume or pea family.
Potpourri: The black locust is indigenous to the lower slopes of the Southern Appalachian Mountains. It has hard, strong, handsome dark brown wood that is virtually impervious to fungal decay. The longevity of locust wood is an article of faith in the lore and legend of agrarian society; locust fence posts reportedly lasting for over one hundred years and pioneer homes with locust corner posts still standing. It was used in
virtually any application calling for high strength and durability, notably tool handles, dowels and pins to fasten the planks to the ribs of wooden ships, hubs for wagon wheels, and gates. Due to its resistance to decay, it was also used as an alternative to teakwood for ship decking, paneling and floorboards. The aesthetic appearance of the wood led to its use in furniture, notably tabletops and music cabinets. However, the quality of Locust tree wood is dependent on a number of environmental conditions. When grown in poor soils, the wood is harder and denser due the slower growth relative to faster growing trees in fertile soils, which tend to be brittle. Forest grown Locust trees produce straight, limbless trunks; those grown in the open tend to be crooked and forked.
Since Black Locust is a legume, it has specialized bacteria living in swellings called root nodules. These bacteria reduce free nitrogen from the air to produce ammonia, which is “fixed” in the soil, and which can then be used by other crops to improve their yield. The robust root structure rapidly spreads from an original parent tree to produce groves of clones through the process of root suckering. This led to its promotion by state and federal agencies as a means of erosion control, particularly in areas of coal strip mine reclamation. It is considered a threat to vegetation outside its native range due to its aggressive, rapid growth. It is difficult to control because trying to eradicate it by plowing or digging so as to damage the roots only serves to further accelerate the growth.
Because of its many attributes, the Locust tree has been spread by the conscious actions of good-intentioned arborists throughout the world. It was one of the first New World trees to be exported to Europe, entering England in the 1630’s. Ebenezer Jessup proposed that ten thousand acres of Locust trees be planted for the British Navy in 1791. In the early 1800’s William Corbett, the author of The English Gardener, promoted the Locust tree, predicting that it would eventually replace all hardwoods in Britain. He established nurseries that sold the trees at inflated prices. However, the zeal abated when the resultant trees were found to be excessively brittle and forked, probably due to the environmental factors of soil condition and tree density. The Locust tree has been a great success as an introduced tree in Israel, China, the Himalayas and New Zealand. In Korea, it is used as a biomass source in fuel-wood plantations due to its rapid growth. A fifth of Hungary’s forests are planted with the Locust tree, predominantly a cultivar named “Shipmast Locust” that originated in New York.
The resistance of the Locust tree to decay is due to chemicals that it produces that are toxic to some forms of life, particularly insects and fungi. Some testing has been done to try to isolate these chemicals, for potential use as natural wood preservatives. High concentrations of a flavenoid called robinetin and a fungal growth inhibitor called taxifolin are thought to play a role. Ironically, parts of the locust tree are consumed as food by both humans and animals. Honey produced by bees from Locust tree nectar is considered among the finest in the world; the Robinia or Acacia Honey from the Danube River basin is of worldwide renown The seed pods are edible when cooked, and the flowers are used to make fritters and are added as a flavoring to pancake batter.. Locust leaves are used for animal fodder in the Himalayas and Bulgaria.
The toxicity of the Locust tree is also responsible for its historic use as a treatment for disease. The Cherokee Indians chewed the root bark to induce vomiting and to ameliorate the pain of a toothache. The flowers contain the glycoside robinin, which has been shown experimentally to act as a diuretic. A tea made from the flowers was used to treat everything from headache to nausea. Juice from the leaves purportedly inhibited viruses.