Black locust (Robinia pseudoacacia)
The black locust (Robinia pseudoacacia) belongs to the pea family (Fabaceae), in a subfamily called Mimosoideae.
It is also known as the False Acacia, the Locust Tree or Robinia.
The black locust is originally at home in the south-eastern region of North America. In 1492, it was introduced into Europe, where it is now cultivated in a wide range of locations. Natural regeneration occurs mainly in areas with high temperatures during the vegetation period.
Description of the wood
The very thin layer of sapwood, often only up to 1 cm, is bright yellow to greenish in colour and clearly differs from the heartwood, which can be of a range of different colours. When freshly cut, it is usually yellowish green to greenish brown, though it darkens under exposure to sunlight to become golden brown or sometimes even chocolate brown. When planed, its surface has a shiny golden appearance. The wood is very hard, even harder than oak, elastic and very tough. The basic density is, on average, 0.74 g/cm³ at 15 % wood moisture content. This makes the black locust one of the heaviest native timbers.
The black locust is good or moderate to work, usually by sawing. In contrast, it is excellently suited to turnery work. For nails and screws, holes should be drilled as the wood is hard and tough.
Black locust wood is more resistant and durable than oak. The heartwood is very durable to durable (durability class 1 – 2, acc. to DIN EN 350-2) in its resistance to wood-destroying fungi and termites, though it is at risk from wood-destroying insects.
The heartwood of the black locust is practically untreatable (treatability class 4, acc. to DIN EN 350-2), the sapwood however is permeable and easy to treat.
The availability of black locust wood is limited. Trees which are long, strong and straight-growing are scarce, so this robust wood is mostly put to use in a small range of special applications. These are usually uses which place particularly high demands on hardness, strength and durability. Besides its use as a constructional timber for special applications, black locust wood is also used in barrels, tool handles, fences, posts and bars. Because it is an excellent wood for turning, it is used for making nails for ships, in glazing and shoe-making tasks, and for sports equipment.