Locust, or False Acacia – Robinia pseudoacacia

Trees & ShrubsFlowering Trees & Shrubs – Robinia / Locust, or False Acacia – Robinia pseudoacacia (syn Robinia pseudacacia)

Robinia pseudoacacia, also known in its native territory as black locust, is a tree of the genus Robinia in the subfamily Faboideae of the pea family Fabaceae. It is native to the southeastern United States, but has been widely planted and naturalized elsewhere in temperate North America, Europe, Southern Africa and Asia and is considered an invasive species in some areas. Another common name is false acacia, a literal translation of the specific name. It was introduced into Britain in 1636. (Wikipedia)

The Locust Tree (Robinia pseudacacia) (Edward Step)

Although the Locust, or False Acacia, is little planted now, it is only paying the penalty for having had its merits enormously exaggerated; just as human reputations sometimes sink into oblivion after a season of popularity achieved by the persistent “booming” of influential friends. The friend in this case was William Cobbett, who, on his return from the United States, about 1820, preached salvation to the timber grower through the planting of Robinia; “nothing in the timber way could be so great a benefit as the general cultivation of this tree.” So great was the demand thus created that Cobbett himself started a nursery for the propagation and supply of Robinias, and so great is the virtue of a name that people refused the Locust-trees that every nurseryman had in stock and wished to sell, and would be content with nothing but Cobbett’s Robinias, which could not be produced fast enough for the demand! They thought it was an entirely new introduction, though it had been grown in this country as an ornamental tree for nearly two centuries! Its wood is hard, strong, and durable, but liable to crack, and of limited utility.

The Locust was introduced to Europe from North America early in the seventeenth century, and was then thought to be identical with the African Acacia. Linnæus named the genus in honour of Jean Robin, a French botanist, whose son, an official at the Jardin des Plantes, was the first to cultivate the tree in Europe.

It is a tree of light and graceful proportions, its branches being long and slender, and the long narrow leaves being broken up into a large number of small oval leaflets, arranged pinnately, that is, feather-wise. The stipules, which are found at the base of the leaf-stalk in many plants, are in this genus converted into sharp spines. The flowers, of similar pea-shape to those of the Laburnum, are white and fragrant. They are in long loose racemes, which droop from the axils of the leaves in May. The legumes are very thin, and of a dark-brown hue.

This was one of the first American trees introduced to Europe, and its name of Locust came with it, the missionaries believing it must be the tree upon whose fruit, with the addition of wild honey, John the Baptist supported himself in the wilderness. It is also known as Silver Chain, in contradistinction to the Gold Chain or Laburnum; also as White Laburnum.

Webster listed the following Robinia in the 19th century.

R. PSEUD-ACACIA.—Common Locust, Bastard Acacia, or False Acacia. North America, 1640. A noble-growing and handsome tree, with smooth shoots, and stipules that become transformed into sharp, stiff spines. The flowers are in long racemes, pure-white or slightly tinged with pink, and with a faint pleasing odour. This species has been sub-divided into a great number of varieties, some of which are very distinct, but the majority are not sufficiently so to warrant special attention. The following include the best and most popular kinds:—R. Pseud-Acacia Decaisneana, a distinct form bearing light pinky flowers; R. Pseud-Acacia Bessoniana, with thornless branches and a dense head of refreshing Pea-green foliage; R. Pseud-Acacia angustifolia, with narrow leaves; R. Pseud-Acacia aurea, a conspicuous but not very constant golden leaved form; R. Pseud-Acacia inermis, of which there are weeping, upright, and broad-leaved forms, has narrow leaves that are glaucous beneath, and the characteristic spines of the species are wanting or rarely well developed. R. Pseud-Acacia monophylla is very distinct, the leaves being entire instead of pinnate; while R. Pseud-Acacia crispa has curiously-curled foliage. Then there is the peculiar R. Pseud-Acacia tortuosa, of ungainly habit; R. Pseud-Acacia umbraculifera, with a spreading head; R. Pseud-Acacia sophoraefolia, the leaves of which resemble those of Sophora japonica; and R. Pseud-Acacia amorphaefolia, with very large foliage when compared with the parent tree. The above may be taken as the most distinct and desirable forms of the False Acacia, but there are many others, such as R. Pseud-Acacia colutoides, R. Pseud-Acacia semperflorens, and R. Pseud-Acacia Rhederi, all more or less distinct from the typical tree.

ROBINIA DUBIA (syns R. echiuata and R. ambigua).—A very pretty garden hybrid form, said to have for its parentage R. Pseud-Acacia and R. viscosa. It is of quite tree-like growth and habit, with unusually short spines, and Pea-green foliage. The flowers are produced pretty freely, and are of a pale rose colour, and well set off by the light-green leaves, over which they hang in neat and compact spikes.

R. HISPIDA.—Rose Acacia. North America, 1743. Amongst large-growing shrubs this is certainly one of the most distinct and handsome, and at the same time one of the hardiest and readiest of culture. Under favourable conditions it grows about 16 feet high, with large oval or oblong leaflets, and having the young branches densely clothed with bristles. The flowers, which are individually larger than those of the False Acacia, are of a beautiful rosy-pink, and produced in June and July. It is a very ornamental, small growing species, and one that is peculiarly suitable for planting where space is limited. R. hispida macrophylla (Large-leaved Rose Acacia) is rendered distinct by its generally more robust growth, and by its larger foliage and flowers. The species, however, varies a good deal in respect of the size of leaves and flowers.

R. VISCOSA (syn R. glutinosa).—Clammy Locust. North America, 1797. This is a small-growing tree, and readily distinguished by the clammy bark of the younger shoots. Flowers in short racemes, and of a beautiful rose-pink, but varying a good deal in depth of tint. It is a valuable species for ornamental planting, and flowers well even in a young state.

Few soils would seem to come amiss to the Acacias, but observations made in many parts of the country conclusively prove that the finest specimens are growing on light, rich loam overlying a bed of gravel. They are propagated from seed, by layers, or by grafting.

Not considered an invasive species in Britain.