The False Acacia or Black Locust, Robinia pseudo-acacia, (L.) is a fascinating and common tree much planted both in the United States (it comes from the Southeastern states, in particular the Appalachian and Ozark mountains), in Europe, and other parts of the world. There is a Black Locust among the five "Old Lions" of Kew. In China it is called the "Foreign Scholar Tree". It is generally regarded as a very elegant landscape tree indeed. Robinia is a genus currently restricted to North America, but traces of it do occur in Europe from Eocene and Miocene rocks. It is sometimes referred to as the tree on which America was built. When the first European settlers arrived they found it already planted where the local inhabitants lived, the various peoples having planted it from the mountains of the interior, as it was used by them in a variety of ways, including bow-making. The settlers used it extensively for building and many other uses.
It is one of the genera that does form nitrogen-fixing nodules on its roots - and it is often used in mine-spoil reclamation. The young trees grow well and vigorously, but in the U.S. they are then often infected by locust borers, at least beyond its home range, which greatly reduces its potential as a timber tree. Overseas it shows quite interesting potential. The wood if harvested young is excellent for firewood. The timber is also tough, extremely hard and rot-resistant, due to flavenoids in the heartwood. Abraham Lincoln is said to have been among the many who have produced thousands of posts and split-rail fences from this tree.
The leaves and bark are toxic, but the seeds and young pods may be edible, cooked or perhaps uncooked. The tree is often used for honey production, which is reputedly delicious, but there is often an unreliable supply, year by year. The species is unsuitable for small gardens (Philip Hurling take note!) due to its large size, rapid growth and tendency to throw up root suckers, but the cultivar ‘Frisia’, a selection with bright yellow-green leaves throughout the summer, is occasionally planted as an ornamental tree. At the moment it appears to be suffering from a widespread but unexplained disease.
The genus is named after M. Jean Robin, and his son Vespasian, French royal gardeners of the 16th century. It was much planted in England in part due to the importation of seed from the States by William Cobbett (of Rural Rides) in the early 19th Century. It has also been said, incorrectly, that the Americans won the war of 1812 - 1815 against the British because their ships were held together with locust nails, while the British ships were held together with oak nails, and the American ships therefore survived cannonball impact so much better, that after the war the Americans made a great trade in selling locust nails to the British Navy, which insisted on them from 1813 onwards. Although this may have been partly used as an excuse for bad leadership, the locust nails did swell very effectively when wet, making their fixings fully waterproof!
The racemes of flowers which appear at the start of summer are said to smell of orange blossoms, and are edible. The colour may be whitish, pink or even apparently purple. The leaflets are said to fold together at night or when it rains - but I have never seen this! The mature shoots may carry thornless leaves, others have small paired stipular thorns of 1-2 mm. long, while the vigorous young shoots may have their stipular thorns of up to 2 cm. long.
The leaves are pinnate, 10 - 25 cm. long with 9 - 19 oval leaflets, blue-green in colour. Each leaflet may have a blunt or indented tip, with an absolutely tiny, soft spine at the very apex, only just visible. You can see the dark red colour of the young shoots behind and to the leaf, not always easy to pick out! These features tend to separate this tree from the honey locust, which has vicious spines, including often large clusters on the trunk!
The leaves are slender and hairy, with swollen bases (covering the buds of the next year's growth) - these can be seen in the pictures below.
The thorns on either side of one of the swollen stipule bases can just be seen here.
The pods are 5 - 10 cm long and dark brown, containing 4 - 10 seeds.
The bark is stated on Wikipedia to be dark grey-brown, tinged with red, deeply furrowed, with the surface inclined to scale. This particular tree is quite small and appears relatively young. The orange-red here appears mainly at the bottom of the furrows.
I have seen other photos on the internet that demonstrate a craggier bark, perhaps on older trees.
It is one of the genera that does form nitrogen-fixing nodules on its roots - and it is often used in mine-spoil reclamation. The young trees grow well and vigorously, but in the U.S. they are then often infected by locust borers, at least beyond its home range, which greatly reduces its potential as a timber tree. Overseas it shows quite interesting potential. The wood if harvested young is excellent for firewood. The timber is also tough, extremely hard and rot-resistant, due to flavenoids in the heartwood. Abraham Lincoln is said to have been among the many who have produced thousands of posts and split-rail fences from this tree.
The leaves and bark are toxic, but the seeds and young pods may be edible, cooked or perhaps uncooked. The tree is often used for honey production, which is reputedly delicious, but there is often an unreliable supply, year by year. The species is unsuitable for small gardens (Philip Hurling take note!) due to its large size, rapid growth and tendency to throw up root suckers, but the cultivar ‘Frisia’, a selection with bright yellow-green leaves throughout the summer, is occasionally planted as an ornamental tree. At the moment it appears to be suffering from a widespread but unexplained disease.
The genus is named after M. Jean Robin, and his son Vespasian, French royal gardeners of the 16th century. It was much planted in England in part due to the importation of seed from the States by William Cobbett (of Rural Rides) in the early 19th Century. It has also been said, incorrectly, that the Americans won the war of 1812 - 1815 against the British because their ships were held together with locust nails, while the British ships were held together with oak nails, and the American ships therefore survived cannonball impact so much better, that after the war the Americans made a great trade in selling locust nails to the British Navy, which insisted on them from 1813 onwards. Although this may have been partly used as an excuse for bad leadership, the locust nails did swell very effectively when wet, making their fixings fully waterproof!
The racemes of flowers which appear at the start of summer are said to smell of orange blossoms, and are edible. The colour may be whitish, pink or even apparently purple. The leaflets are said to fold together at night or when it rains - but I have never seen this! The mature shoots may carry thornless leaves, others have small paired stipular thorns of 1-2 mm. long, while the vigorous young shoots may have their stipular thorns of up to 2 cm. long.
The leaves are pinnate, 10 - 25 cm. long with 9 - 19 oval leaflets, blue-green in colour. Each leaflet may have a blunt or indented tip, with an absolutely tiny, soft spine at the very apex, only just visible. You can see the dark red colour of the young shoots behind and to the leaf, not always easy to pick out! These features tend to separate this tree from the honey locust, which has vicious spines, including often large clusters on the trunk!
The leaves are slender and hairy, with swollen bases (covering the buds of the next year's growth) - these can be seen in the pictures below.
The thorns on either side of one of the swollen stipule bases can just be seen here.
The pods are 5 - 10 cm long and dark brown, containing 4 - 10 seeds.
The bark is stated on Wikipedia to be dark grey-brown, tinged with red, deeply furrowed, with the surface inclined to scale. This particular tree is quite small and appears relatively young. The orange-red here appears mainly at the bottom of the furrows.
I have seen other photos on the internet that demonstrate a craggier bark, perhaps on older trees.
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