Botanical Name: Robinia pseudacacia
Species: R. pseudoacacia
Synonyms: Locust Tree
Common Names: Black Locust, Yellow Locust, False acacia
Habitat:Robinia pseudacacia is native to Eastern N. America – Appalachian and Ozark mountain ranges. Naturalized in Britain . It grows in woods and thickets, especially in deep well-drained calcareous soils.
Robinia pseudoacacia is a deciduous Tree growing to 25 m (82ft) by 15 m (49ft) at a fast rate. Exceptionally, it may grow up to 52 metres (171 ft) tall and 1.6 metres (5.2 ft) diameter in very old trees. It is a very upright tree with a straight trunk and narrow crown which grows scraggly with age. The dark blue-green compound leaves with a contrasting lighter underside give this tree a beautiful appearance in the wind and contribute to its grace.
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Black locust is a shade intolerant species and therefore is typical of young woodlands disturbed areas where sunlight is plentiful and soil is dry, in this sense, black locust can often grow as a weed tree. It also often spreads by underground shoots or suckers which contribute to the weedy character of this species. Young trees are often spiny, however, mature trees often lack spines. In the early summer black locust flowers; the flowers are large and appear in large, intensely fragrant (reminiscent of orange blossoms), clusters. The leaflets fold together in wet weather and at night (nyctinasty) as some change of position at night is a habit of the entire leguminous family.
Description in detail:
*Bark: The bark is dark gray brown and tinged with red or orange in the grooves. It is deeply furrowed into grooves and ridges which run up and down the trunk and often cross and form diamond shapes.
*Root: The roots of black locust contain nodules which allow it to fix nitrogen as is common within the pea family.
The branches are typically zig-zagy and may have ridges and grooves or may be round. When young, they are at first coated with white silvery down, this soon disappears and they become pale green and afterward reddish or greenish brown.
Prickles: :Prickles may or may not be present on young trees, root suckers, and branches near the ground; typically, branches high above the ground rarely contain prickles. R. psuedoacacia is quite variable in the quantity and amount of prickles present as some trees are densely prickly and other trees have no prickles at all. The prickles typically remain on the tree until the young thin bark to which they are attached is replaced by the thicker mature bark. They develop from stipules (small leaf like structures which grow at the base of leaves) and since stipules are paired at the base of leaves, the prickles will be paired at the bases of leaves. They range from .25–.8 inches (0.64–2.03 cm) in length and are somewhat triangular with a flared base and sharp point. Their color is of a dark purple and they adhere only to the bark.
*Wood: Pale yellowish brown; heavy, hard, strong, close-grained and very durable in contact with the ground. The wood has a specific gravity of 0.7333, and a weight of approximately 45.7 pounds per cubic foot.
* Leaves: The leaves are compound, meaning that each leaf contains many smaller leaf like structures called leaflets, the leaflets are roughly paired on either side of the stem which runs through the leaf (rachis) and there is typically one leaflet at the tip of the leaf (odd pinnate). The leaves are alternately arranged on the stem. Each leaf is 6–14 inches (15–36 cm) long and contains 9-19 leaflets, each being 1–2 inches (2.5–5.1 cm)long, and .25–.75 inches (0.64–1.91 cm) wide. The leaflets are rounded or slightly indented at the tip and typically rounded at the base. 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 is grooved and swollen at the base. The stipules are linear, downy, membranous at first and occasionally develop into prickles. The leaves appear relatively late in spring.
The leave 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.
*Flower: The flowers open in May or June for 7–10 days, after the leaves have developed. They are arranged in loose drooping clumps (racemes) which are typically 4–8 inches (10–20 cm) long. The flowers themselves are cream-white (rarely pink or purple) with a pale yellow blotch in the center and imperfectly papilionaceous in shape. They are about 1 inch (2.5 cm) wide, very fragrant, and produce large amounts of nectar. Each flower is perfect, having both stamens and a pistil (male and female parts). There are 10 stamens enclosed within the petals; these are fused together in a diadelphous configuration, where the filaments of 9 are all joined to form a tube and one stamen is separate and above the joined stamens. The single ovary is superior and contains several ovules. Below each flower is a calyx which looks like leafy tube between the flower and the stem. It is made from fused sepals and is dark green and may be blotched with red. The pedicels (stems which connect the flower to the branch) are slender, .5 inches (1.3 cm), dark red or reddish green.
*Fruit: The fruit is a typical legume fruit, being a flat and smooth pea-like pod 2–4 inches (5.1–10.2 cm) long and .5 inches (1.3 cm) broad. The fruit usually contains 4-8 seeds. 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.
*Winter buds: Minute, naked (having no scales covering them), three or four together, protected in a depression by a scale-like covering lined on the inner surface with a thick coat of tomentum and opening in early spring. When the buds are forming they are covered by the swollen base of the petiole.
*Cotyledons are oval in shape and fleshy.
Landscape Uses:Erosion control, Firewood, Aggressive surface roots possible. Succeeds in any well-drained soil, preferring one that is not too rich. Succeeds in dry barren sites, tolerating drought and atmospheric pollution. Succeeds in a hot dry position. The plant is reported to tolerate an annual precipitation in the range of 61 to 191cm, an annual temperature in the range of 7.6 to 20.3°C and a pH of 6.0 to 7.0. A fast-growing tree for the first 30 years of its life, it can begin to flower when only 6 years old, though 10 – 12 years is more normal. The flowers are a rich source of nectar and are very fragrant with a vanilla-like scent. The branches are brittle and very liable to wind damage. When plants are grown in rich soils they produce coarse and rank growth which is even more liable to wind damage. The plants sucker freely and often form dense thickets, the suckers have vicious thorns. There are some named varieties selected for their ornamental value, some of these are thornless. Any pruning should be done in late summer in order to reduce the risk of bleeding. The leaves are rich in tannin and other substances which inhibit the growth of other plants. A very greedy tree, tending to impoverish the soil. (Although a legume, I believe it does not fix atmospheric nitrogen. A very good bee plant. This species is notably resistant to honey fungus. Special Features: North American native, Invasive, Naturalizing, All or parts of this plant are poisonous, Attracts butterflies, Fragrant flowers, Blooms are very showy.
Seed – pre-soak for 48 hours in warm water and sow the seed in late winter in a cold frame. A short stratification improves germination rates and time. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in the following summer. Other reports say that the seed can be sown in an outdoor seedbed in spring. The seed stores for over 10 years. Suckers taken during the dormant season.
Edible Uses: Condiment; Drink; Oil.
Seed – cooked. Oily. They are boiled and used like peas. After boiling the seeds lose their acid taste. The seed is about 4mm long and is produced in pods up to 10cm long that contain 4 – 8 seeds. A nutritional analysis is available. Young seedpods – cooked. The pods contain a sweetish pulp that is safe to eat and is relished by small children. (This report is quite probably mistaken, having been confused with the honey locust, Gleditsia spp.) 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. No further details. All the above entries should be treated with some caution, see the notes at the top of the page regarding toxicity. Flowers – cooked. A fragrant aroma, they are used in making jams and pancakes. They can also be made into a pleasant drink.
Figures in grams (g) or miligrams (mg) per 100g of food.
Seed (Dry weight)
*0 Calories per 100g
*Water : 0%
*Protein: 21g; Fat: 3g; Carbohydrate: 0g; Fibre: 28g; Ash: 6.8g;
*Minerals – Calcium: 1400mg; Phosphorus: 0.3mg; Iron: 0mg; Magnesium: 0mg; Sodium: 0mg; Potassium: 0mg; Zinc: 0mg;
*Vitamins – A: 0mg; Thiamine (B1): 0mg; Riboflavin (B2): 0mg; Niacin: 0mg; B6: 0mg;
Febrifuge. The flowers are antispasmodic, aromatic, diuretic, emollient and laxative. They are cooked and eaten for the treatment of eye ailments. The flower is said to contain the antitumor compound benzoaldehyde. The inner bark and the root bark are emetic, purgative and tonic. The root bark has been chewed to induce vomiting, or held in the mouth to allay toothache, though it is rarely if ever prescribed as a therapeutic agent in Britain. The fruit is narcotic. This probably refers to the seedpod. The leaves are cholagogue and emetic. The leaf juice inhibits viruses.
Tonic, emetic and purgative properties have been ascribed to the root and bark, but the locust tree is rarely, if ever, prescribed as a therapeutic agent.
Occasional cases of poisoning are on record in which boys have chewed the bark and swallowed the juice: the principal symptoms being dryness of the throat, burning pain in the abdomen, dilatation of the pupils, vertigo and muscular twitches; excessive quantities causing also weak and irregular heart action.
Though the leaves of Robinia have also been stated to produce poisonous effects careful examination has failed to detect the presence of any soluble proteid or of alkaloids, and by some the leaves have been recorded as even affording wholesome food for cattle.
The flowers contain a glucoside, Robinin, which, on being boiled with acids, is resolved into sugar and quercetin.
Dye; Essential; Fibre; Fuel; Oil; Soil stabilization; Wood.
A drying oil is obtained from the seed. An essential oil is obtained from the flowers. Highly valued, it is used in perfumery. A yellow dye is obtained from the bark. Robinetin is a strong dyestuff yielding with different mordants different shades similar to those obtained with fisetin, quercetin, and myricetin; with aluminum mordant, it dyes cotton to a brown-orange shade. The bark contains tannin, but not in sufficient quantity for utilization. On a 10% moisture basis, the bark contains 7.2% tannin and the heartwood of young trees 5.7%. The bark is used to make paper and is a substitute for silk and wool. Trees sucker freely, especially if coppiced, and they can be used for stabilizing banks etc. Wood – close-grained, exceedingly hard, heavy, very strong, resists shock and is very durable in contact with the soil. It weighs 45lb per cubic foot and is used in shipbuilding and for making fence posts, treenails, floors etc. A very good fuel, but it should be used with caution because it flares up and projects sparks. The wood of Robinia pseudoacacia var. rectissima, the so called ‘Long Island’ or ‘Shipmast’ locust, has a greater resistance to decay and wood borers, outlasting other locust posts and stakes by 50 – 100% .
Known Hazards: All parts of the plant (except the flowers) and especially the bark, should be considered to be toxic. The toxins are destroyed by heat. The inner bark contains a poisonous proteid substance, Robin, which possesses strong emetic and purgative properties. It is capable of coagulating the casein of milk and of clotting the red corpuscles of certain animals.
Disclaimer : The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplement, it is always advisable to consult with your own health care provider.