Taxonomic name: Robinia pseudoacacia (L.)
Synonyms: Robinia pseudoacacia var. rectissima (L.) Raber
Common names: acacia blanc (French-Reunion (La Réunion)), black locust (English), false acacia (English), Post locust (English), robinia akacjowa (Polish), robinier (French), robinier faux acacia (French), robinier faux-acacia (French-France), yellow locust (English)
Organism type: tree
Robinia pseudoacacia is a leguminous deciduous tree native to the southeastern United States that has been widely introduced to other parts of North America. It is commonly found in disturbed areas such as old fields, degraded woods, forest edges, and roadsides, but it poses the greatest threat to dry and sand prairies and oak savannas. R. pseudoacacia has been planted on reclaimed land to control erosion and has been used for ornamental purposes. It reproduces vigorously by root suckering and stump sprouting to form groves of trees interconnected by a common root system.
R. pseudoacacia is described as a leguminous deciduous tree that grows from 30 to 80 feet tall. Young saplings have smooth, green bark; older trees have deep, furrowed, shaggy, dark bark with flat-topped ridges. Leaves are alternate and pinnately compound with 7 to 21 leaflets. Leaflets are thin, elliptical, dark green above, and pale beneath. Flowers are pea-like, fragrant, white to yellow, and born in large, drooping racemes. Seed pods are shiny, smooth, narrow, flat, 5cms to 10cms long, and contain 4 to 8 seeds (DNR, 2003). Smaller branches are armed with a pair of setaceous stipules, or stipular spines, that occur at the base of each petiole. These stipular spines are very pronounced on resprouts, and make working among these plants somewhat hazardous (Gover, pers. comm., 2004).
Gleditsia triacanthos, Sophora japonica
agricultural areas, natural forests, planted forests, range/grasslands, ruderal/disturbed
R. pseudoacacia is an early successional plant, preferring full sun, well drained soils, and little competition. It invades dry and sand prairies, oak savannas, and upland forest edges. R. pseudoacacia is commonly found in disturbed areas such as old fields, degraded woods, and roadsides (Weiseler, 1998).
Once introduced, R. pseudoacacia expands readily into areas where their shade reduces competition from other (sun-loving) plants. Dense clones of R. pseudoacacia create shaded islands with little ground vegetation. Lack of ground fuel limits the use of fire in natural disturbance regimes. The large, fragrant blossoms of R. pseudoacacia compete with native plants for pollinating bees.
DNR (2003) states that the wood of R. pseudoacacia is valued for its durability and high fuel value, and the tree also provides good forage for bees. R. pseudoacacia is planted on reclaimed land to control erosion and has been used for ornamental purposes.
Native range: R. pseudoacacia is reported to be native to the southeastern United States (lower slopes of the Appalachian Mountains with separate outliers north along the slopes and forest edges of southern Illinois, Indiana, and Missouri).
Known introduced range: Outside of its native range, R. pseudoacacia has become naturalized throughout the United States. It has also been reported in a few Canadian provinces (Converse, 1984). It has been reported as invasive in Cyprus, Korea and Italy.
Introduction pathways to new locations
For ornamental purposes: According to OPLIN (2001), R. pseudoacacia has been used for ornamental purposes.
Landscape/fauna "improvement": According to OPLIN (2001), R. pseudoacacia is planted on reclaimed land and to control erosion.
Local dispersal methods
Natural dispersal (local): Successful reproduction via vegetative runners has contributed to the naturalisation of black locust in upland forests, prairies, and savannas (DNR, 2003).
R. pseudoacacia produces shoots from its root system, so any control effort should be targeted against the roots (Art Gover Aliens-L., 2002).
For details on management of this species, please see management information
Wieseler (1998) states that R. pseudoacacia reproduces vigorously by root suckering and stump sprouting to form groves (or clones) of trees interconnected by a common fibrous root system.
According to Converse (1984), R. pseudoacacia is a good seed producer, with heavy seed crops at 1- or 2- year intervals and light crops in the intervening years. Best seed crops occur when the trees are between 15 and 40 years of age, but some trees will bear at 6 years and some as late as 60 years.
Reviewed by: Art Gover, PENNDOT Roadside Vegetation Management Project. Department of Horticulture, The Pennsylvania State University USA
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Friday, 17 June 2005