Traditional Uses and benefits of Black Locust

Robinia pseudoacacia, commonly known in its native territory as black locust, false acacia or post locust are actually a medium-sized tree, belonging to the tribe Robinieae and pea (Fabaceae) family. The plant is native to few small areas of the Eastern United States, but it has been widely planted and naturalized elsewhere in temperate North America, Europe, Southern Africa, Australia, New Zealand, Asia, other parts of North America  and is considered an invasive species in some areas. Due to its durability, adaptability to highly disturbed sites and because it burns well for firewood, it became a popular tree to plant in the early 1900s throughout North America. Black locust tree, Chinese scholar tree, common robinia, false acacia, locust tree, robinia, ship-mast locust, yellow locust, post locust, white acacia, acacia locust, honey locust, white locust, locust are some of the popular common names of the plant. Common name false acacia is a literal translation of the specific name (pseudo meaning fake or false and acacia referring to the genus of plants with the same name).

Genus name honors Jean Robin (1550-1629), of Paris, gardener to Henri IV and Louis XIII of France, who received new plants from Canada. A specific epithet pseudoacacia means false acacia. The name locust is said to have been given to Robinia by Jesuit missionaries. The Bible tells the story of how John the Baptist was kept alive in the wasteland by eating ‘locusts’, which were not the insects, but the pods of the Carob tree, which have some similarity to locusts. When the Christian immigrants discovered Robinia which has roughly similar pods, they were also called Locust tree. The tree’s fast-growing nature makes it widespread for mine reclamation, reforestation and erosion control, and it is still one of the most widely planted trees in North America. Black locust is commonly used for fence posts, mine timbers, poles, railroad ties, insulator pins, ship timber, nails for wooden ship construction, pulp, boxes, crates, etc. It is also a popular choice for woodworking projects, as the wood is naturally resistant to most rots.

Black Locust Facts

Plant Description

Black locust is a medium-sized, fast-growing, hardwood, deciduous, root suckering tree with a straight trunk and narrow crown that grows scraggly with age. The plant normally grows about 40–100 feet (12–30 m) with a diameter of 2–4 feet (0.61–1.22 m). Exceptionally, it may grow up to 52 meters (171 ft.) tall and 1.6 meters (5.2 ft.) diameter in very old trees. The plant is found growing in a forests, riparian habitats, grassland, rocky places, waste places, scrubland, forest margins and clearings, woods and thickets, dry prairies, sand prairies, savannas, riverbanks, roadsides, disturbed sites, gardens, urban bush land, open woodlands in temperate and sub-tropical regions. The plant grows in a variety of soils, except that extremely dry or compact plastic soils are undesirable. Limestone soils are especially favorable, and soils without pronounced subsoil development are best.

Roots

The extensive network of fibrous, lateral roots produce suckers. Radial roots typically extend 1 to 1.5 times the tree height, though lengths of 50 m have been documented. Taproots are rare but have been documented at lengths of up to 7.6 m with deep lateral roots.

Stems

Stems tend to be straight in forests but with spreading, curvy branches in open areas. The bark of young trees is brown or greenish, smooth and with conspicuous lenticels (pores) and spines. It becomes deeply tan or gray-brown and eventually becomes deeply furrowed with flat-topped ridges in older trees. The inner bark is orange. Two large spines 5-25 mm long with broad bases (i.e. stipular spines) are present near the base of some or all of its leaves.

Leaves

The alternately arranged leaves are 8-15 cm long and are once-compound (i.e. pinnate) and borne on stalks (i.e. petioles) 14-45 mm long. These leaves have several to numerous nearly 11-21 leaflets, which are borne on tiny stalks (i.e. petiolules) 1-3 mm long. The leaflets are 2-6 cm long and 1-2.8 cm wide and are oval (i.e. elliptic) or oblong in shape with entire margins and rounded or slightly notched tips (i.e. obtuse or emarginate apices). They are hairless (i.e. glabrous) or sometimes sparsely hairy (i.e. puberulent) when young.

The leaves come out of the bud folded in half, yellow green, covered with silvery down which soon disappears. Each leaflet initially has a minute stipel, which quickly falls, and is connected to the (rachis) by a short stem or petiolule. The leaves are attached to the branch with slender hairy petioles which are grooved and swollen at the base. The stipules are linear, downy, and membranous at first and occasionally develop into prickles. The leaves appear relatively late in spring. The leaf color of the fully grown leaves is a dull dark green above and paler beneath. In the fall the leaves turn a clear pale yellow.

Leaf arrangement	Alternate
Leaf type	Odd pinnately compound
Leaflet margin	Entire
Leaflet shape	Elliptic (oval); oblong; obovate
Leaflet venation	Pinnate
Leaf type and persistence	Deciduous
Leaflet blade length & Breadth	About 2-6 cm long and 1-2.8 cm wide
Leaf color	Dark green
Fall color	Pale Yellow
Fall characteristic	Not showy

 

Flower

The pea-shaped flowers are arranged in elongated clusters (10-15 cm long) that are borne in the leaf forks (i.e. in axillary racemes). These flowers are predominantly white, occasionally pink or purple and are borne on stalks (i.e. pedicels) 5-10 mm long. They have five hairy sepals 5-9 mm long that are fused together at the base (i.e. into a calyx tube) and five petals 15-20 mm long. The uppermost petal (i.e. standard) is larger, often with some greenish markings at the base. There are also two side petals (i.e. wings) and two lower petals are fused together and folded (i.e. a keel). The flowers also have ten stamens, nine of which are fused to each other and one of which is separate, and an elongated ovary that is topped with a style and stigma. Flowering occurs mostly during spring and early summer (i.e. from September to December).

Flower color	Predominantly white, occasionally pink or purple
Flower characteristics	Pleasant fragrance; spring flowering; very showy

 

Fruit

Fertile flowers are followed by elongated and flattened pea-like pod that are 3-8 cm long and 10-15 mm wide. Fruits are initially green turning to brown in color as it matures. These fruit are hairless (i.e. glabrous) and split open when mature to release seeds. The fruit usually consists of 4-8 seeds.

Fruit shape	Elongated and flattened Pod
Fruit length & Breadth	3-8 cm long and 10-15 mm wide
Fruit covering	Dry or hard
Fruit color	Green turning to brown as it matures
Fruit characteristics	Attracts birds; attracts squirrels and other mammals; inconspicuous and not showy; fruit, twigs, or foliage cause significant litter; persistent on the tree

 

Seeds

Seed pods consists of 4 to 8 flat, bean-like toxic seeds each about 3 to 5 mm long. The seeds are dark orange brown with irregular markings. They ripen late in autumn and hang on the branches until early spring. There are typically 25500 seeds per pound.

History

Black locust is native to the eastern United States, but the exact native range is not accurately known as the tree has been cultivated and is currently found across the continent, in all the lower 48 states, eastern Canada, and British Columbia. The native range is supposed to be two separate populations; one centered about the Appalachian Mountains, from Pennsylvania to northern Georgia, and a second westward focused around the Ozark Plateau and Ouachita Mountains of Arkansas, Oklahoma and Missouri.

Black locust’s current range has been expanded by humans distributing the tree for landscaping and now includes Pakistan, India, Australia, Canada, China, Europe, Northern and South Africa, temperate regions in Asia, New Zealand, and Southern South America. In Australia black locust has become naturalized within Victoria, New South Wales, South, and Western Australia. It is considered an environmental weed there. In South Africa, it is regarded as a weed because of its suckering habit.

Traditional uses and benefits of Black Locust

• Flowers are antispasmodic, aromatic, diuretic, emollient and laxative.
• They are cooked and eaten for the treatment of eye ailments.
• Flower is said to consist of the antitumor compound benzoaldehyde.
• Inner bark and the root bark are emetic, purgative and tonic.
• Root bark has been chewed to induce vomiting, or held in the mouth to allay toothache.
• The fruit is narcotic.
• The leaves are cholagogue and emetic.
• The leaf juice prevents viruses.
• In traditional medicine of India, different parts of R. pseudoacacia are used as laxative, antispasmodic, and diuretic.
• Dried leaves are helpful in treatment of wounds caused by burns.
• When used internally, it calms stomach burns, and is usually recommended to individuals who suffer from hyperacid gastritis and distensions.
• Black Locust is excellent in treatments of asthma and bronchitis.
• It could be very useful in cases of headaches and stress.
• Infusion added to baths can help young children who suffer from insomnia.
• Flower powder is used in cases of gastritis, duodenal and gastric ulcer.
• Many people chew the root bark of the tree to bring out vomiting and it is also retained in the mouth to alleviate toothache.
• Seed pods, have narcotic properties and are often used as an analgesic.
• Bark of young branches is used in the treatment of fevers and migraine.

Therapeutic Uses of Black Locust

Various parts of the black locust tree have different uses. They can be used to purify the body, cure spasms and encourage proper flow of bile. Some of the well-known health benefits and therapeutic uses of black locust are as follows

• Blossoms of the black locust are known for their diuretic, emollient and anti-spasmodic properties. Some also consume cooked flowers to relieve eye problems. The flowers are even known to contain a chemical which may help to combat tumors. The crushed flowers help in healing of the skin after burns. They may be applied to the affected area and left on for a couple of hours.
• Infusion can be prepared with a teaspoonful of black locust flowers and a cup of water. Drinking this after meals helps to alleviate burning in the stomach and is helpful for people with gastritis.
• Hot black locust tea helps in treating cough, sore throat, bronchitis and asthma.
• Add lime flowers to an infusion of black locust flowers to prepare a relaxing remedy for mental fatigue and nervousness.
• Inner bark and root bark of the black locust helps to remove waste from the body. The root bark is occasionally chewed to induce vomiting. It may also be placed in the mouth to cure a toothache.
• The fruits, berries and seedpods are used as an analgesic due to their narcotic properties.
• Leaves of black locust are known to improve secretion and flow of bile. The juice obtained from the leaves may also help to fight against viruses. The dried leaves may be used to heal burns and wounds.
• Black locust seeds are usually boiled to reduce the bitterness and then consumed. The seedpods may also be eaten as they contain a sweet pulp. The seeds are known to be rich in nutrients.

Culinary Uses

• Seed can be consumed after being cooked.
• They are boiled and used like peas.
• Young seedpods can be cooked.
• A strong, narcotic and intoxicating drink is made from the skin of the fruit.
• Piperonal is extracted from the plant; it is used as a vanilla substitute.
• Flowers can be consumed after being cooked.
• Fragrant aroma of flowers is used in making jams and pancakes.
• They can also be made into a pleasant drink.

Other Facts

• This species has been extensively planted for shelterbelts and windbreaks, and is also used to produce woody biomass for energy production.
• Its main use has been in the rehabilitation of former surface mine sites and for erosion control, but it is also used to rehabilitate contaminated soils, depleted soils, gravel pits, and logged areas, and to stabilize railroad embankments and highway edges.
• The plant is often found as a pioneer on old fields, burned areas, and lands strip-mined for coal.
• Flowers are a rich source of nectar. Honey produced from this nectar is considered to be of high quality and fetches a price premium.
• A drying oil is obtained from the seed.
• An essential oil is obtained from the flowers which is highly valued in perfumery.
• A yellow dye is obtained from the bark.
• Bark is used to make paper and is a substitute for silk and wool.
• Wood is close-grained, exceedingly hard, heavy, and very strong.
• It is considered a very good fuel, but it should be used with caution because it flares up and projects sparks.
• The wood is also used for making charcoal.
• Durable, tough and high quality wood can be used for many purposes, including shipbuilding, fence posts, tree nails, poles, piling, mine props, wall paneling, flooring, fence posts, vine props, woodenware, furniture, fruit boxes, pulp and paper, and biomass energy.
• In South Africa, it is regarded as a weed because of its suckering habit.
• Black locust was one of the first trees to be introduced from America into England.
• The tree has been used in reforestation and to control soil erosion because of its rapid, spreading growth and nitrogen-fixing ability.

Prevention and Control

Control

Black locust is quite difficult to control. Because this species is strongly clonal, all stems in a clone must be treated. It is critical to monitor the site to ensure that cut and treated stumps do not resprout—if a single stem survives, the entire clone may regenerate.

Mechanical control

Control of established black locust populations generally needs the use of herbicide although mechanical control may occasionally boost the effectiveness of other methods.

Hand-pulling/Digging/Bull-dozing

Since most black locust spread is vegetative, and saplings are connected underground, hand-pulling is not useful. In general, damage to the root causes sprouting also. On highly disturbed sites, cutting trees and removing the roots with a bulldozer has been recommended but does not appear practical in most settings.

Cutting/Mowing

Cutting without the use of herbicide produces prolific sprouts and is not advised. In a comparison of cut and uncut sites, those that had been cut had twice the growth rates of those that had not been cut, and began to flower in half the time.

Grazing

In a North Carolina effort, browsing by a combination of cattle and domestic goats effectively controlled the height growth of black locust. After 4 seasons, all black locust were dead. Since black locust can be toxic to cattle, caution is advised. Black locust is raised specifically to feed domestic goats in Pakistan and New Zealand, and they appear to be a better choice for control.

Chemical control

In most cases, effective control of black locust requires the use of herbicide. Factors that should be considered when selecting an herbicide for use on a particular site include proximity to water or wetlands, presence or absence of desirable native vegetation, potential for erosion and the effectiveness of the herbicide under consideration on black locust.

Prescribed burning

In fire-adapted communities, prescribed burning may enhance control of black locust over the long term, but should always be considered as part of an integrated management plan for the site as it will stimulate the species over shorter time spans. When prescribed burning is initiated, it should be supplemented with other control methods.

Biological control

Black locust is susceptible to witches’ broom disease caused by the virus Chlorogenus robiniae as well as fungal diseases that cause heart rot. It is also vulnerable to damage from two native insects, the locust borer (Megacyllene robiniae) and the locust leafminer (Odontota dorsalis).

Precautions

• All parts of the plant (except the flowers) and especially the bark should be considered to be toxic.
• Symptoms of poisoning include dilated pupils, feeble pulse, severe vomiting, and a death-like pallor.
• The plant is also said to be toxic to livestock, though sometimes it is purposely used for forage by farmers etc.
• Horses that consume the plant show signs of anorexia, depression, incontinence, colic, weakness, and cardiac arrhythmia.
• Humans may get dermatitis from exposure to black locust wood.

References:

https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=504804#null

http://www.hear.org/pier/species/robinia_pseudoacacia.htm

https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomydetail?id=5238

https://pfaf.org/user/plant.aspx?latinname=Robinia+pseudoacacia

https://www.cabi.org/isc/datasheet/47698

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=280476

https://www.fs.fed.us/database/feis/plants/tree/robpse/all.html

https://en.wikipedia.org/wiki/Robinia_pseudoacacia

https://wiki.bugwood.org/Robinia_pseudoacacia

https://www.invasiveplantatlas.org/subject.html?sub=3350

http://www.flowersofindia.net/catalog/slides/White%20Locust%20Tree.html

https://gd.eppo.int/taxon/ROBPS

http://www.theplantlist.org/tpl1.1/record/ild-8996

https://hort.purdue.edu/newcrop/duke_energy/Robinia_pseudoacacia.html

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