Not to be semantically confused with :
Honey Locust (Sophora japonica) [a tree of similar name belonging to a differing Genus within the Pea Family (Fabaceae)]
Some similarities to : Laburnum (Laburnum anagyroides) but that has yellow flowers in drooping spikes (racemes).
Uniquely identifiable characteristics
Distinguishing Feature :
No relation to :
False Cypress [a coniferous tree with similar name] or
False Grass-poly, False Fox Sedge,
False Oat-grass. Nor is it an
Acacia, it just looks a bit like one, hence the 'pseudoacacia' part of its scientific name.
It is thought to occur naturally in only 2 locations in the World: the Appalacian Mountains south of Pennsylvania and the Ozark plateau west of Mississippi, which are both in the USA. But it is now widely cultivated worldwide. Its wood is one of the hardest woods of any tree in North America (so the book says, but like most American books, doesn't mention the rest of the world where it also occurs (but not naturally). It was first introduced to Europe in 1601 and to Britain in 1636. In the Royal Botanical Gardens at Kew, it is the oldest tree of known date still in those gardens, although most of the trunk is dead wood held together by metal bands!
The flowering spikes droop in up to 65mm long racemes, shorter than most Laburnums. Only after a hot previous year does the plant produce flowers in early summer, 2013 had a long hot and warm spell so the above tree flowered in 2014. The bark is pale grey and smooth at first but quickly develops deep mostly vertical long fissures and becomes very craggy. The shoots are dark-red, ribbed, with the stronger ones having pairs of sharp spines not easily visible to catch the unwary. Like most, if not all plants of the Fabaceae family, it is capable of fixing its own nitrogen.
It propagates by suckering, only seldom by seed. It sometimes forms thickets and is found in woods, and heaths. It is non-native, introduced into the UK in 1636. Originally native to the SE of USA, it is now found naturalised in the UK, temperate parts of North America, Europe, Asia and South Africa, being regarded as invasive in some regions, such as the UK.
It is poisonous containing
Robin, a phytotoxin and a toxalbumen which inhibits protein synthesis, also
Robitin the glycoside of Robin. Heating Robin destroys its toxicity. The poisons are mostly present in the seeds, young leaves and the inner bark. Robitin is present in the bark at 1% and is a recognised poisoner of cattle, rabbit, and horse the toxic dose in horses being just 1.5mg, 20mg for cattle and 500mg in rabbits. Black Locust also contains another phytotoxin, phasin.
Ingestion can cause anorexia and bloody diarrhoea, cold arms and legs, dilation of pupils, paleness, shock, colic, depression, weakness, tachycardia and irregular heartbeat but it is rarely fatal although the laminitis can be a severe after-effect.
Some of the toxins within the Black Locust are harvested to make pharmaceuticals, as an analgesic and to treat ulcers and intestinal problems.
The flowers can apparently be battered, deep fried then eaten and are toxic only if consumed in large quantities. They are very fragrant and yield an aromatic essential oil that is used to make perfumes. The essential oil is dominated by two ingredients, 2-AminoBenzaldehyde which is present mostly in the flowers and is responsible for their perfumery and 3(Z)-Hexen-1-ol (aka 'Leaf Alcohol' present mostly in the leaves.
Additional constituents are
Robinetin (aka Robinethin) (a flavonoid and colourant contained in the bark which, with alum, can be used as a brownish-orange dye), but their toxicity is not known.
The bark is highly combustible but is apt to release sparks when burning. The Robinetin (and the other flavonols DiRobinetin and Taxifolin [aka 'Toxifolin'?]) within the bark, which comprise up to 6% of the dry weight, render the wood highly resistant to rotting. Compared with Quercetin, another flavonol (but one not found in False Acacia), Taxifolin has low toxicity. The wood is highly prized for its water and weather resistance and its durability, and for this reason is used to build ships hulls, the decking on ships and masts as well as for outdoor posts and roofing. The effectiveness of these inherent flavonols in preserving the wood has been shown to be just as efficacious as impregnation with PentaChloroPhenol or Chromated Copper Arsenate and much more environmentally friendly, containing neither organochlorides, chromium, copper or arsenic.
The tree also contains the non-toxic
Robinin (aka Robinine) (a flavonol glycoside being the triple rhamnoside glycoside of Kaempferol). The kaempferol flavonol moiety is shown in black, the glycoside moieties in red.
The lectins called Robin are poisonous and found within False Acacia, but they are not as toxic as the lectin called
Abrin (which are found in the genus Abrus) nor the lectin called
Ricin (found in the genus Ricinus - the
Castor Oil Plant Ricinus communis).