Named by Linnaeus after a French royal gardener, this thorny tree was introduced to Britain around 1636
Black locust. Jean Robin.
Nature · Trees
Black locust
Neophyte (introduced about 1636) · deciduous to 25 m · streets, parks and waste ground
Robinia pseudoacacia — Fabaceae
A spiny, suckering North American legume with drooping white pea-flower chains in early summer, introduced to Britain around 1636 and hugely promoted by William Cobbett from 1819. Its rot-proof timber and nitrogen-fixing roots are valued, but it spreads by suckers and seeds and is regarded as invasive across much of Europe, so it is one to watch in Britain. All parts other than the flowers are toxic.
How to know it
How to spot them
- ▸Leaves pinnate with 7 to 19 oval, blunt, entire leaflets, each notched at the tip; leaflets fold at night
- ▸Pairs of short, sharp thorns at the base of the leaves
- ▸Hanging chains of sweetly scented white pea flowers in late spring or early summer
- ▸Flat, brown, bean-like pods that persist through winter
- ▸Deeply furrowed, ridged and twisted grey-brown bark
- ▸Look-alikes: tree of heaven has toothed-based leaflets and no thorns; honey locust (Gleditsia) has huge branched thorns. Black locust has paired thorns and untoothed oval leaflets.
How to know it
From 1819 an English pamphleteer promoted it heavily, later calling it 'the tree of trees' and claiming to have sold over a million
Black locust. William Cobbett.
Hanging white pea-flower chains scent the air in early summer, and bees make a pale honey from them
Black locust.
Pairs of short thorns sit at the base of its pinnate leaves, whose leaflets fold at night
Black locust.
Its extremely rot-resistant timber is used for fence posts, and its roots fix nitrogen
Black locust.
Its suckering and abundant seed give it the potential to become invasive, as it has in much of Europe
Black locust (Oxford University Plants 400).
Quick-fire facts
- •Robinia pseudoacacia — named by Linnaeus for Jean Robin (1550–1629), gardener to French kings; pseudoacacia means false acacia
- •Introduced to Britain around 1636; promoted by William Cobbett from 1819, who called it 'the tree of trees' in The Woodlands (1825) and claimed to have sold over a million (Oxford University Plants 400)
- •Native to the south-eastern USA; family Fabaceae, so a nitrogen-fixing legume
- •Suckers and seeds freely; its traits add to its potential as an invasive species, and it is treated as invasive in many European countries
- •Timber is extremely durable and rot-resistant
- •Bark, leaves and seeds are toxic; the flowers are eaten in parts of Europe, but do not experiment
- •The golden-leaved 'Frisia' is a common garden cultivar
- •No notifiable pest specific to it is a current concern in Britain
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Sources
- Oxford University Plants 400 — Robinia pseudoacacia