Black Locust is native to the southeastern United States, but has been widely planted and naturalized elsewhere in temperate North America, Europe and Asia. A less frequently used common name is False Acacia, which is a literal translation of the specific epithet. It was introduced into Britain in 1636.
Description
It grows to 14 – 25m tall, with a trunk up to 0.8 m diameter (exceptionally up to 27 m tall and 1.6 m diameter in very old trees), with thick, deeply furrowed blackish bark. The leaves are 10 – 25cm long, pinnate with 9–19 oval leaflets, 2–5 cm long and 1.5 – 3cm broad. Each leaf usually has a pair of short thorns at the base, 1 – 2mm long or absent on adult crown shoots, up to 2 cm long on vigorous young plants. The intensely fragrant flowers are white, borne in pendulous racemes 8–20 cm long, and are considered edible. The fruit is a legume 5 – 10cm long, containing 4 – 10 seeds.
Although similar in general appearance to Honey locust, it lacks that tree's characteristic long branched spines on the trunk, instead having the pairs of short thorns at the base of each leaf; the leaflets are also much broader.
Cultivation
In Europe it is often planted alongside streets and in parks, especially in large cities, because it tolerates pollution well. The species is unsuitable for small gardens due to its large size and rapid growth. Black locust has nitrogen-fixing bacteria on its root system; for this reason it can grow on poor soils and is an early colonizer of disturbed areas.
Toxicity
Like the honey locust, the black locust reproduces through its distinct hanging pods, but on the black locust they are smaller and lighter and thus easily carried long distances by the wind. Unlike the pods of the honey locust, but like those of the related European Laburnum, the black locust's pods are toxic.
