Black locust

Latin Name: Robinia pseudoacacia

locust_flowers_robAlternative Name(s): False acacia, Locust tree, Yellow locust, Robinia

Family: Fabaceae

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.

Habitat: Woods and thickets, especially in deep well-drained calcareous soils.

Edibility Rating: 3 (1-5)

Medicinal Rating: 2 (1-5)

locust_small_branchPhysical Characteristics: Robinia is a small genus of about twenty species of trees and large shrubs usually with spines on the branches. Leaves have many leaflets giving a fine tracery when viewed upwards. Sweetly perfumed, white pea-like flowers borne in tresses are followed by small brown pods with several seeds.
The flowers are hermaphrodite (has both male and female organs) and are pollinated by Bees. It can fix Nitrogen. It is noted for attracting wildlife.

Edible Uses

Edible Parts: Flowers; Seed; Seedpod. 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.

Medicinal Uses

Antispasmodic; Antiviral; Aromatic; Cancer; Cholagogue; Diuretic; Emetic; Emollient; Febrifuge; Laxative; Narcotic; Purgative; Tonic. 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.


Other Uses

Dye; Essential; Fibre; Fuel; 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%.

Notes: Black locust produces root suckers when the roots are disturbed and dense clumps may develop crowding out other plants. It was often planted around homesteads and stockyards and sometimes the dense thicket is the living reminder of former farming ventures.
Although native to North America it has become naturalised in Europe forming thickets in disturbed land along roadsides and railways and reducing the view of the surrounding countryside for travellers. It has transformed grassland into open woodland in parts of Germany.
The characteristics which make it weedy have been used to advantage in erosion control work in Hungary. The roots also fix nitrogen in the soil.
Black locust is naturalised in WA, SA, Victoria, NSW and Queensland. It was sometimes planted in Canberra last century as a street tree and is a scattered weed in the ACT. It is still available in nurseries although ‘mop top’ cultivars are now more popular for small gardens. It is still used as the rootstock however and the problem of suckering has been reduced but not solved.

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