History in the United States
Black locust has been planted extensively for its nitrogen fixing abilities, as a source of nectar for honeybees, and for fenceposts and hardwood lumber. The clonal pattern of growth and connected roots are promoted for erosion control. It is also used for mine soil reclamation. Black locust is susceptible to some damage from two native insects, the locust borer (Megacyllene robiniae) and the locust leafminer (Odontota dorsalis).
J. C. Huntley
Black locust (Robinia pseudoacacia), sometimes called yellow locust, grows naturally on a wide range of sites but does best on rich moist limestone soils. It has escaped cultivation and become naturalized throughout eastern North America and parts of the West.
Black locust is not a commercial timber species but is useful for many other purposes. Because it is a nitrogen fixer and has rapid juvenile growth, it is widely planted as an ornamental, for shelterbelts, and for land reclamation. It is suitable for fuelwood and pulp and provides cover for wildlife, browse for deer, and cavities for birds.
Black locust has a shallow, aggressive root system. The bark of black locust is deeply furrowed and is dark reddish-brown to black in color. It has an alternate branching pattern, which creates a zigzag effect. A pair of sharp thorns grows at each node. They are ½ to ¾ inches long, and very stout.
The pinnately compound leaves are 8 to 14 inches long, with 7 to 19 short stalked leaflets. These dull green leaflets are ovoid or oval, 1 to 2 inches long, thin, scabrous above and pale below.
The separate male and female plants have sweetly fragrant flowers that are creamy white with five petals (bean-like) arranged in a pyramidal spike. They usually bloom in May or June. Heavy seed production can be expected annually or biannually. The legume type seed is produced in a flat, brown to black pod, which is 2 to 4 inches long. There is an average of 25,500 seeds per pound. Although black locust is a good seed producer, its primary means of spread is by both rudimentary and adventitious root suckers.
False acacia, yellow locust
Regularity: Regularly occurring
Regularity: Regularly occurring
Range and Habitat in Illinois
Black locust is native to the United States, though the extent of its original range is not accurately known. It is thought that black locust was originally found in 2 regions. The eastern region was centered in the Appalachian Mountains and ranged from central Pennsylvania and southern Ohio south to northeastern Alabama, northern Georgia, and northwestern South Carolina. The western region included the Ozark Plateau of southern Missouri, northern Arkansas, and northeastern Oklahoma and the Ouachita Mountains of central Arkansas and southeastern Oklahoma. It is thought that outlying native populations existed in southern Indiana and Illinois, Kentucky, Alabama, and Georgia (review by ). The US Geological Survey provides a distributional map of black locust's native range in North America.
Black locust has been widely planted and frequently escapes cultivation ([53,123,124,128,190,215,325,360], review by ). As of 2009, it occurred throughout the conterminous United States and a number of Canadian provinces. Plants Database provides a map of black locust's distribution in North America. Black locust also occurs in parts of South America, Europe, Asia, Africa, and Australia (review by ).
Distribution in the United States
Black locust has been planted in many temperate climates and is naturalized throughout the United States, within and outside of its historical range, and in some parts of Europe.
central Arkansas and southeastern Oklahoma. Outlying populations appear in southern Indiana and Illinois, Kentucky, Alabama, and Georgia (26). Black locust has been planted widely and has become naturalized throughout the United States, southern Canada, and parts of Europe and Asia.
-The native range of black locust.
Distribution and adaptation
Black locust’s native range follows the Appalachian Mountains from Pennsylvania to Alabama, and a secondary population exists primarily in the Ozark Mountains. Black locust is adapted to a wide variety of soil types, but grows best on sites that are deep, well drained, and derived from limestone. This tree tolerates a pH range of 4.6 to 8.2. It is commonly found on south and west slopes in West Virginia.
For a current distribution map, please consult the Plant Profile page for this species on the PLANTS Website.
Black locust is a fast growing tree that can reach 40 to 100 feet in height at maturity. While the bark of young saplings is smooth and green, mature trees can be distinguished by bark that is dark brown and deeply furrowed, with flat-topped ridges. Seedlings and sprouts grow rapidly and are easily identified by long paired thorns. Leaves of black locust alternate along stems and are composed of seven to twenty one smaller leaf segments called leaflets. Leaflets are oval to rounded in outline, dark green above and pale beneath. Fragrant white flowers appear in drooping clusters in May and June and have a yellow blotch on the uppermost petal. Fruit pods are smooth, 2 to 4 inches long, and contain 4 to 8 seeds. Two other locusts native to the Appalachians, Robinia viscosa (with pink flowers), and Robinia hispida (with rose-purple flowers), are used in cultivation and may share black locusts invasive tendencies.
Catalog Number: US 462258
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): C. G. Pringle
Year Collected: 1906
Locality: Valley near Tula., Hidalgo, Mexico, North America
Elevation (m): 2073 to 2073
- Holotype: Rose, J. N. 1909. Contr. U.S. Natl. Herb. 12: 274.
Catalog Number: US 1177134
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): C. G. Pringle
Year Collected: 1906
Locality: Valley near Tula., Hidalgo, Mexico, North America
Elevation (m): 2073 to 2073
- Isotype: Rose, J. N. 1909. Contr. U.S. Natl. Herb. 12: 274.
Habitat and Ecology
Range and Habitat in Illinois
General In its native range, black locust occurs in a wide range of forest communities (see Habitat types and plant communities for specific community associations), as well as a variety of disturbed sites such as old fields ([169,225,332], reviews by [167,314]) and logged areas [15,46,184,220,228,288,317]. It generally occurs at low density within the forest interior but establishes well in forest openings, edges , and other early-successional habitats. See Successional Status for more information.
Elevation: A silvics guide states that in its native range, black locust thrives best on moist slopes of the eastern mountains below 3,400 feet (1,040 m) (review by ). It occurs below 300 feet (90 m) in parts of Kentucky  and Tennessee  and above 4,000 feet (1,200 m) in Great Smoky Mountains National Park (, review by ).
Soils: Black locust occurs in a variety of soil types within its native range. Numerous sources associate black locust with limestone ([39,41,121,172,268,311], reviews by [167,312]), but it is also associated with sandstone , chert , and mica-gneiss substrates . Soils tend to be loams (, reviews by )) or sandy loams . Other soil characteristics associated with black locust include "rich" (, reviews by [167,312]), deep (, review by ), well-drained ([2,38,129], review by ), and moist (, review by ) conditions.
Black locust may not grow well on very sandy, very acid, or wet soils (review by ). It is sensitive to soil conditions that produce either minimal or excessive aeration and drainage (reviews by [66,167]). Black locust growth is limited by water-logged soils or soil compaction (review by ).
In its native range, black locust tolerates a range of soil acidities; a pH of 4.6 to 8.2 is listed as "acceptable" in 2 reviews [26,167]. Soil at a site within its native range in the Nantahala Mountains of western North Carolina had a pH of 4.7 . In the Great Smoky Mountains of Tennessee and North Carolina, black locust was found in soils with a pH of 5 .
Topography: Black locust is often found on slope forests within its native range ([1,2,29,211,350], review by ). In the Monongahela National Forest in central West Virginia, black locust occurred on slopes of 45% to 55% . In the Nantahala Mountains of western North Carolina, it occurred on a 21.6° slope . Black locust has been found on northwestern slopes in eastern West Virginia  and southerly slopes in North Carolina and Tennessee .
Black locust occurs in a variety of forest types in the Black and Craggy Mountains of western North Carolina, though at very low densities .
Relative density of black locust in xeric to mesic oak forests 
Percent density of all trees
mixed-oaks, yellow-poplar, red maple, American beech, hickories
2,500-3,400 ft, moderately sheltered low ridges, flats and valleys, dry-mesic, moderate nutrients
white oak, American beech, red maple
well-drained valley flats and terraces,
scarlet oak, red maple, sourwood
<3,400 ft, south- and west-facing ridges, slopes, and flats, dry-mesic, intermediate in nutrients and pH
Northern red oak, chestnut oak, yellow-poplar
northern red oak, chestnut oak, yellow- poplar, red maple
3,200-4,000 ft, open slopes of all aspects, intermediate nutrients and pH
chestnut oak, scarlet oak, black oak, northern red oak, pignut hickory, red maple, black tupelo
3,000-4,500 ft, south- and southwest-facing slopes and narrow ridges of most aspects, xeric, nutrient poor
northern red oak, red maple, sweet birch, American beech, eastern hemlock
4,000-5,000 ft, middle and upper slopes, ridgetops, intermediate in moisture and nutrients
Relative density of black locust in mesic to wet forests 
Percent density of all trees
sugar maple, basswood, American beech, yellow buckeye (Aesculus flava), yellow birch
<5,000 ft, low, predominantly north-facing slopes, coves, and sheltered slopes, wet-mesic, high nutrients and pH
Northern red oak
northern red oak, yellow-poplar, sugar maple, eastern hemlock, American beech
slopes adjacent to cove forests, slightly lower moisture, nutrients and pH compared to cove forests
American sycamore, yellow birch, eastern hemlock, red maple
floodplains and terraces of large streams, mesic, moderate nutrients
yellow birch, eastern hemlock, red maple, sweet birch, witch-hazel (Hamamelis virginiana)
slopes and hollows adjacent to mesic red oak forests, upstream from alluvial forests, 1st- and 2nd-order stream flats and in ravines, mesic, low nutrients and pH
Climate: Climate conditions in black locust's native range are humid, though it has been successfully introduced into many parts of the world where climate conditions vary widely from those listed below (review by ).
Climate conditions for black locust's native range (review by )
|January normal daily temperatures||-7 to 2 °C||2 to 13 °C|
|August normal daily temperatures||13 to 21 °C||27 to 32 °C|
|Mean length of average frost-free period||150 days||210 days|
|Normal annual total precipitation||1,020 mm||1,830 mm|
|Mean annual total snowfall||5 cm||152 cm|
General Outside of its native range, black locust thrives in disturbed ([12,91,210,231,237,272], review by ) or "waste" areas [31,329]. Specific examples of disturbed areas include roadsides ([53,85,113,128,153,215,329], reviews by [26,72]), railroad right-of-ways , constructed wetland edges , disturbed hammock margins , man-made sandflats , and channel levees .
Many disturbed black locust sites are also associated with human habitation and agricultural operations. Black locust occurs in fencerows and hedgerows ([85,113,124,143,161,325,329,341], review by ), abandoned agricultural fields [60,80,97,160,165,210,237,327,329,332] and pastures ([113,128,313], review by ), and near old home or farm sites [53,152,153,156,192,198,231,231,325,341].
Black locust spreads from disturbed sites into areas such as forests ([58,113,116,161,232,329], forest edges [124,165], reviews by [71,72]), woodlands , woodland openings , thickets [128,232], or prairies and other grasslands (, review by [72,173,289]). See Habitat types and plant communities for descriptions of plant communities where black locust occurs outside its native range.
Black locust often establishes in riparian areas such as stream- and riverbanks and floodplain forests throughout its nonnative range, including locations in the Southeast [77,294], Northeast [12,116,200,224,254,332], Great Lakes , Northern Great Plains , Northern and Central Rockies [91,192] Northwest [17,156,198,259], Southwest (review by ), and California ([73,94,111,152,153,197,279,296], reviews by [26,95,290]).
Elevation: In its nonnative range, black locust is found at a wide range of elevations. The following table demonstrates that black locust may occur anywhere from 30 to 6,500 feet (10-2,000 m) in its nonnative range.
|30-350||southeastern Louisiana |
|80-240||central Maryland |
|160-6,300||California (, review by )|
|1,000||southwestern Wisconsin |
|3,115-3,135||Grand Canyon National Park, Arizona (review by )|
|3,770||Las Cruces, New Mexico |
|4,450||midwestern Himalaya of India |
|4,920-7,545||southwestern New Mexico |
|5,000-6,200||Sierra Nevada, California |
|6,500||New Mexico (review by )|
Soils: In its nonnative range, black locust is found in a wider range of soil conditions than within its native range. An association with limestone or calcareous soil is noted in the Southwest , the Northeast, and Canada . In contrast to its native range, a strong association with sandy soils is found in the Northern Great Plains , north-central Texas , Illinois [5,133], the Northeast , Maryland , California (, review by ), and Hungary (, review by ). Many of these locations are either sand dunes or sand prairies [5,133], or stream or river deposits [236,254,296]. Black locust was found on fertile loam near the Sacramento River in California , Richfield silty loam in the high plains regions of the Oklahoma panhandle , silty-clay loam in eastern Nebraska , well-drained loams in eastern Washington and northern Idaho , and silty or sandy loams with loose structure in Hungary (review by ). Clayey soils were listed as "inappropriate" in Hungary (review by ), and sandy or constantly wet soils were not conducive to growth in eastern Washington and northern Idaho .
A preference for moist sites is noted in the Northern Great Plains , northern United States and southern Canada , and Hungary (review by ). Black locust's deep rooting ability may allow it to grow in locations much drier than in its native range (review by ). Black locust was one of the most abundant trees establishing in dense stands on "poor", dry soils on man-made sandflats along the Hudson River in eastern New York . Several sources suggest that as in its native range, black locust does best on well-drained sites ([313,325], review by ). One source states that black locust prefers deep soils in the Southwest , though another states that it may grow well on shallow soils in the Northeast (review by ). Black locust is found on sites that range from low (, review by ) to intermediate  and high  soil fertility in its nonnative range. The ability of black locust to establish and persist in areas with low soil nutrient levels (like the pitch pine-scrub oak forest type in New York  or dry grasslands in Europe (, review by )) is highly problematic to land managers (see Impacts).
Black locust has been planted on soils with a wide range of pH and tolerates extremely acidic soils, particularly in strip-mine reclamation sites . For example, 21% of 1- to 2-year-old black locust seedlings survived soil pH as low as 2.85 on acid strip-mine spoil in southwest Indiana, though higher survival was observed when lime was added to raise the pH . One biofuel plantation site in Las Cruces, New Mexico, had a soil pH of 7.9 .
Topography: Black locust is commonly found on slopes across its native and nonnative ranges. In southwestern Michigan, it occurred on the south slope of a large moraine . In Ohio, black locust was most abundant on dry hillsides . In California, it was locally abundant on canyon slopes . In the Palouse prairie region of eastern Washington and northern Idaho, black locust occurred on hills and slopes too steep to plow .
Climate: Black locust is highly susceptible to frost and cold weather damage (reviews by [167,312]), which may limit expansion of its range. Black locusts planted in Ontario were limited by hard winter frosts that killed new growth . Frost is listed as the most important abiotic threat to black locust in Hungary; it may damage shoots and decrease growth, leading to dwarfed trees over time (review by ).
Few authors report climate data for areas where black locust has either been planted or established outside its native range. Plantations of black locust were started in Las Cruces, New Mexico, an area with a minimum winter temperature of 18.1 °F (-7.7 °C) and a maximum summer temperature of 100.9 °F (38.3 °C) . Near Albany, New York, black locust established in a region with average temperatures of 21 °F (-6 °C) in January and 72 °F (22 °C) in June . Black locust also established in western Maine, where January temperatures ranged from 4.5 to 27.0 °F (-15.3 to -2.8 °C) and July temperatures ranged from 54.7 to 80.8 °F (12.6-27.1 °C) .
Black locust grows well in the Palouse prairie region of eastern Washington and northern Idaho, where average annual high and low temperatures for Moscow, Idaho, are 58.1 °F (14.5 °C) and 35.8 °F (2.1 °C) respectively, and average annual high and low temperatures for Colfax, Washington, are 59.9 °F (15.5 °C) and 36.5 °F (2.5 °C) respectively. This area infrequently experiences long periods of subzero temperatures in the winter .
Low precipitation may also limit black locust persistence or range expansion. Only 8% of black locust survived that were planted in the sagebrush desert of south-central Oregon, an area receiving less than 10 inches (250 mm) of annual precipitation (review by ). For rehabilitation in Utah, a reclamation handbook notes that black locust grows as a shrub at temperate climate sites that receive more than 12 inches (305 mm) of annual precipitation, and as a small tree at sites receiving more than 15 inches (380 mm) of annual precipitation (review by ). Black locust was found in southwestern Wisconsin, an area with an average annual precipitation of 30.6 inches (777.2 mm) , as well as in western Maine, where average annual precipitation was 44 inches (1,116 mm) .
Habitat in the United States
Black locust is an early successional plant, preferring full sun, well drained soils and little competition. It is commonly found in disturbed areas such as old fields, degraded woods, and roadsides. Due to its rapid growth, black locust has been promoted by state and federal agencies and nurseries, and is sometimes planted in or near prairies, oak savannas and native woodland edges.
Soils and Topography
Black locust is very sensitive to poorly drained or compact plastic soils. Excessively dry sites are also poor for the species. Yellow, brown, or reddish-brown subsoils without pronounced mottling are better than gray, bluish-gray, or yellow subsoils mottled any color. Silt loams, sandy loams, and the lighter textured soils are superior to clay, silty clay loams, and the heavier soils. In the Central States, growth of black locust plantations was found to be closely correlated to plasticity, compactness, and structure of the subsoil, all of which influence drainage and aeration. Growth was unfavorably affected by insufficient or excessive drainage. Soil pH from 4.6 to 8.2 and the amount of mineral nutrients present showed no relationship to growth. Growth was best on limestone-derived soils and soils without pronounced subsoil development (37).
On West Virginia spoil banks, black locust was the most successful species, but survival declined as slope increased. On slopes greater than 25 percent, each 10 percent increase in slope decreased survival 3.4 percent. On slopes steeper than 40 percent, growth was inversely related to slope steepness. Survival was about 80 percent at elevations of 340 to 670 m (1,100 to 2,200 ft). Above 670 m (2,200 ft), survival decreased steadily with increasing elevation and at 1330 m (4,350 ft) survival was less than 65 percent (7).
Although black locust has done well in mine spoil banks in the Central States, it has failed consistently when planted on badly eroded, compacted, clayey soils of the southern Appalachian Region (21). In the Arkansas Ozarks, many plantations on worn out and eroded fields were complete failures. On the southwestern Coastal Plain of Arkansas, plantations on sites previously in agricultural crops failed because of slow growth due to low soil fertility, repeated attacks by the locust borer (Megacyllene robiniae), and invasion of pine (32).
Native black locust appears under the following ranges of climatic conditions (45). January normal daily temperatures: maximum, 2° to 13° C (36° to 55° F); minimum, -7° to 2° C (20° to 36° F); average -4° to 7° C (25° to 45° F); August normal daily temperatures: maximum, 27° to 32° C (81° to 90° F); minimum, 13° to 21° C (55° to 70° F); average, 18° to 27° C (64° to 81° F); mean length of frost-free period, 150 to 210 days; normal annual total precipitation, 1020 to 1830 mm (40 to 72 in); mean annual total snowfall, 5 to 152 em (2 to 60 in). Black locust has been successfully introduced into many parts of the world where the climatic conditions are different from those of its native range.
Due to the ease of vegetative reproduction, black locust is seldom grown from seed. If seedling production is desirable, the hard seed coat must first be reduced or broken to allow germination; this can be done with sulfuric acid or hot water. Once treated, the seed can be sown on raised nursery beds or directly on to field sites. Black locust seed combined in grass and legume mixtures can be broadcast, drilled, hydroseeded, or aircraft dispersed. Limit locust to 3 pounds per acre in such mixtures.
Black locust is easily propagated from softwood, hardwood, and root cuttings. Preparing 6 to 12 inch hardwood cuttings, collected while dormant is often the most effective procedure. This form of cutting responds well to root-inducing chemicals. Grafting is also a viable propagation option to maintain varietal integrity.
Flower-Visiting Insects and Birds of Black Locust in Illinois
(Hummingbirds & insects suck nectar; butterflies & moths are non-pollinating; all observations are from Robertson)
Trochilidae: Archilochus colubris sn fq
Apidae (Apinae): Apis mellifera sn; Apidae (Bombini): Bombus auricomus sn fq, Bombus fraternus sn, Bombus griseocallis sn, Bombus impatiens sn fq, Bombus pensylvanica sn fq; Anthophoridae (Eucerini): Synhalonia speciosa sn
Nymphalidae: Danaus plexippus sn np; Papilionidae: Papilio marcellus sn np
Sphingidae: Hyles lineata sn np
immersed in bark, in clusters of 2-5, stromatic pseudothecium of Aglaospora profusa is saprobic on dead twig of Robinia pseudoacacia
Remarks: season: 10-1
In Great Britain and/or Ireland:
Foodplant / parasite
fruitbody of Agrocybe cylindracea parasitises branch of Robinia pseudoacacia
Other: minor host/prey
Foodplant / pathogen
Armillaria mellea s.l. infects and damages Robinia pseudoacacia
Foodplant / internal feeder
larva of Bruchidius cisti feeds within pod wall of Robinia pseudoacacia
Remarks: Other: uncertain
Plant / associate
adult of Bruchidius varius is associated with Robinia pseudoacacia
Remarks: season: (late 7-early 10, late 4)5-6
Fungus / saprobe
pycnidium of Camarosporium coelomycetous anamorph of Camarosporium robiniae is saprobic on dead wood of Robinia pseudoacacia
Foodplant / saprobe
clustered or linear, subiculate pseudothecium of Cucurbitaria elongata is saprobic on dead twig of Robinia pseudoacacia
Foodplant / saprobe
immersed, plurilocular stroma of Cytosporina coelomycetous anamorph of Cytosporina ludibunda p.p. (Robinia form) is saprobic on branch of Robinia pseudoacacia
Foodplant / saprobe
immersed, in small groups perithecium of Diaporthe oncostoma is saprobic on dead twig of Robinia pseudoacacia
Remarks: season: 12-2
Foodplant / saprobe
fruitbody of Ganoderma australe is saprobic on dead trunk of Robinia pseudoacacia
Foodplant / parasite
fruitbody of Ganoderma lucidum parasitises live stump of Robinia pseudoacacia
Other: minor host/prey
Foodplant / saprobe
sometimes effuse Gliocladium anamorph of Gliocladium roseum is saprobic on wood of Robinia pseudoacacia
Foodplant / saprobe
fruitbody of Meripilus giganteus is saprobic on dead trunk (large) of Robinia pseudoacacia
Fungus / parasite
Microsphaera pseudacaciae parasitises Robinia pseudoacacia
Foodplant / saprobe
stromatic perithecium of Nectria pallidula is saprobic on dead twig of Robinia pseudoacacia
Remarks: season: 8-1
Foodplant / open feeder
larva of Nematus tibialis grazes on leaf of Robinia pseudoacacia
Other: sole host/prey
Foodplant / gall
larva of Obolodiplosis robiniae causes gall of rolled leaf margin of Robinia pseudoacacia
Foodplant / parasite
fruitbody of Perenniporia fraxinea parasitises live trunk (base) of Robinia pseudoacacia
Other: minor host/prey
Foodplant / spot causer
amphigenous, numerous, very small, scattered, immersed, pallid acervulus of Phloeospora coelomycetous anamorph of Phloeospora robiniae causes spots on live, fading leaf of Robinia pseudoacacia
Remarks: season: autumn
Foodplant / feeds on
gregarious to linearly arranged, covered, then raising and bursting pycnidium of Phomopsis coelomycetous anamorph of Phomopsis oncostoma feeds on branch of Robinia pseudoacacia
Remarks: season: 1-7
Foodplant / feeds on
crowded or solitary, embedded in rows, then erumpent pycnidium of Phomopsis coelomycetous anamorph of Phomopsis petiolorum feeds on branch of Robinia pseudoacacia
Foodplant / gall
Phytoplasma (ined) causes gall of twig of Robinia pseudoacacia
Foodplant / saprobe
fruitbody of Rigidoporus ulmarius is saprobic on dead, white-rotted stump (large) of Robinia pseudoacacia
Foodplant / pathogen
Robinia Mosaic virus infects and damages mosiaced, deformed leaf of Robinia pseudoacacia
Foodplant / hemiparasite
haustorium of Viscum album is hemiparasitic on branch of Robinia pseudoacacia
Associated Forest Cover
In the forest cover type Black Locust (Society of American Foresters Type 50) the species is in pure stands or makes up the majority of stocking (15). Black locust is listed as an associate in only two other types: Yellow-Poplar (Type 57) and Yellow-Poplar-White Oak-Northern Red Oak (Type 59). Black locust is a pioneer type, usually man-influenced, and temporary. It follows disturbances and may be natural or planted. The type is found locally throughout the Eastern United States and in southern Canada. Black locust makes up a majority of the stand during early stages but is short lived and seldom matures to a sawtimber stand. A wide variety of species become associated with black locust and usually replace most of it. On good sites, single trees or small groups may persist, grow to a large size, and form a small part of the ultimate canopy layer.
Diseases and Parasites
Locust borer attacks can begin at a young age and damage can be so extensive that trees are not suitable for fence posts. Many plantations planted in reclamation projects were seriously damaged, but more trees could be used if cut as soon as they reach post or mine-prop size. Slow-growing trees on poor sites are most susceptible to borer attack. On sites where tree vigor is low, repeated attacks often reduce black locust to sprout clumps. Damage to the sprouts is often as severe as in the original stem (37).
Outbreaks of the locust leafminer (Odontota dorsalis) occur almost yearly. Black locust trees throughout an entire region are often defoliated, and during years of low rainfall many are killed. Attacks by the locust twig borer (Ecdytolopha insiticiana) occur over a wide area and in heavily infested areas seedling mortality may be high. Black locust is attacked by a wide variety of other insects that cause some degree of damage (3).
Common diseases are heart rot and witches' broom disease, caused by a virus, Chlorogenus robiniae. In the southern Appalachians most large trees are infected with heart rot and decay of trunk wood is extensive. In the Texas root-rot belt, black locust is extremely susceptible to Phymatotrichum omnivorum (21). In New Brunswick, plantings of black locust are not recommended because of high mortality and dieback of branches caused by Nectria cinnabarina and because of superior performance by conifer species (40).
Although black locust is moderately frost hardy in the southern and central Plains, cold weather damage has occurred in the colder parts of its range (37). In the Appalachian region, it is highly susceptible to frost damage (44). Although the species has been reported to be very susceptible to fire damage, researchers concluded that parts of a study area in Illinois would be rapidly converted to black locust thickets if fire was the only management tool used (2).
Fuels and Fire Regimes
Fuels: Outside its native range, black locust may alter fuels in 2 ways that influence FIRE REGIMES. First, black locust may increase the extent and relative density of forest compared to native plant communities. This change in structure was noted specifically in open habitats in the Northeast and mid-Atlantic states [83,273], and is likely of concern in other open habitats where black locust establishes. Second, black locust may produce a litter layer that differs from that produced by native vegetation. Natural and planted stands of 21- to 35-year-old black locust in Illinois, Indiana, and Ohio contained 10,200 dry-weight pounds of litter/acre . On the Albany Pine Bush Preserve in New York, black locust stands had a 2-fold greater litterfall mass compared to native vegetation . Black locust litter decomposes quickly [9,272] and is generally moist, which may differ from the litter characteristics of native vegetation . One author suggests that black locust stands in pitch pine-scrub oak forests have higher live:dead fuel ratios and fuel moisture than native vegetation, slowing surface fire rate-of-spread and consequently altering FIRE REGIMES . It is therefore unclear whether the quantity of litter represents an increased fuel load or the characteristics of the litter represent a decreased fuel hazard.
FIRE REGIMES: Vegetation in the native range of black locust was historically maintained by a variety of disturbances, including fire (see Successional Status for more information on disturbances). Black locust is well adapted to disturbances such as fire (see FIRE ADAPTATIONS AND PLANT RESPONSE TO FIRE), and fires in these ecosystems likely played a historical role in black locust establishment.
The current distribution of black locust includes ecosystems that historically experienced both frequent and infrequent fires of various severities. The impacts of black locust on these FIRE REGIMES is largely unknown, though there is some concern that black locust may alter FIRE REGIMES in fire-adapted ecosystems like the pitch pine-scrub oak forests in the Northeast. In these systems, black locust is less flammable than the vegetation it is replacing . Some managers even consider black locust "nonflammable" . In a series of laboratory trials, black locust had significantly lower combustion rates and total heat release than pitch pine (P<0.0001) . Black locust litter lies flat on the forest floor and tends to stay relatively damp due to the closed-canopy conditions under dense stands. High live:dead fuel ratios and fuel moistures develop under these stands, which may slow surface fires . These characteristics lead a number of authors to suggest that fire intensity, fire-return intervals, and FIRE REGIMES may be altered in pitch pine-scrub oak forests where black locust is established [81,83,90]. In pitch pine sites, black locust may lengthen the fire-return interval to an unsustainable level, with pitch pine eventually being shaded out along with native fire-adapted understory plants . In this and other ecosystems, black locust also facilitates the establishment of nonnative grasses and other invasive species [82,90,133,252], which might further alter FIRE REGIMES.
See the Fire Regime Table for further information on FIRE REGIMES of vegetation communities in which black locust may occur in its native and nonnative ranges.
Vegetative regeneration is important to the establishment, spread, and persistence of black locust. It is thought to be a more common means of reproduction than seed (reviews by [26,131,314]). Black locust commonly sprouts from roots [90,102,133,156,239,258,272,291,306,363] or the stump ([90,102,108,291,306,365], reviews by [72,167,226]). Sprouting often occurs in response to stem or root damage (, reviews by [167,226]) due to cutting ([108,306,365], reviews by [72,167]), fire ([108,133], review by ), wind, or disease (review by ). Root sprouting is also a common means of reproduction following logging treatments [15,363] and a means of spread into revegetating reclamation sites  and out of plantations and into abandoned fields .
Root sprouting usually begins when plants are 4 to 5 years old (reviews by [131,167]) and increases rapidly in full sun, open areas, and particularly in sandy soils (review by ). Though sprouting is a common response to disturbance, sprouts need sufficient light to survive .
See Physical and/or mechanical control for more information on how black locust's regenerative abilities impact control efforts.
Seedling establishment and plant growth
Establishment: Black locust requires open conditions for establishment ([252,297], reviews by [167,314]). Establishment is often linked to natural ([37,164], review by ) and manmade ([99,103,285], review by ) disturbances. See Successional Status for more information on this topic.
Growth rate: Black locust is known for its rapid juvenile growth rate ([24,59,126,137,202,291,361], review by ). In mixed-oak, cove, and northern hardwood forests in North Carolina, the 5-year average radial growth rate for black locust was 1.31 mm/yr, which was the highest of the 7 species tested . The growth rate of black locust seedlings is limited by plant density (, review by ) and insect infestations [120,365] and enhanced by light , moisture [23,185], and fertilization [23,365].
In its native range, black locust grows rapidly following disturbances such as logging or mining. In regenerating hardwood forests in North Carolina, black locust seedlings grew 26 feet (8 m) in 3 years. They grew faster than any other species for 10 to 20 years . Black locust had the second-tallest mean height of dominant hardwood species 5 years after clearcut treatments in mixed-oak stands in Virginia, with trees as tall as 8.6 feet (2.6 m) . After overstory removal in Pennsylvania mixed-oak stands, black locust seedlings were 3.4 feet (1.0 m) tall 1 year after treatment and 8.1 feet (2.5 m) tall 4 years after treatment . On limestone and acid-shale mine sites in Ohio, direct-seeded black locust reached an average height of 25 feet (8 m) in 7 years, which was higher than any other plant species .
Black locust growth rates are also high in its nonnative range. A review states that black locust growth rates in plantations in the central states could average as much as 42 feet (12.8 m) in 10 years, 68 feet (20.7 m) in 25 years, and 84 feet (25.6 m) in 40 years . In experimental old-field rehabilitation plantations in Iowa, 12- to 15-year-old black locust had the highest annual height growth (µ=2.47 feet (0.75 m)) of any species planted . On mine reclamation sites in southeast Kansas, black locust had the fasted growth of all planted species, growing 23 feet (7 m) in 10 years .
Density: Black locust may grow at high or low densities depending on local site characteristics. Within its native range, seedling densities are variable. There are often few seedlings under canopies containing mature black locust [172,297]. Black locust seedling density was 125 seedlings/ha in an old-growth mixed-hardwood forest in West Virginia . In contrast, in the Nantahala National Forest in North Carolina, oak-hickory-poplar forest gaps created by clearcutting contained numerous black locust seedlings (3,854 seedlings/ha) and sprouts (2,616 sprouts/ha) 2 years after treatment .
Within mature forests of its native range, black locust usually occurs as a canopy tree at low density [1,2,7,40,47,88,92,106,172,205]. For example, there were significantly more black locust stems in 35-year-old, second-growth (22.3 stems/ha) compared to old-growth (4.1 stems/ha) mixed-hardwood forest in eastern Kentucky (P<0.05) . See Successional Status for more information.
In its nonnative range, black locust trees may establish in high densities outside of plantation settings ([231,252], reviews by [72,226]). In a disturbed forest regenerating after a horticultural area was abandoned in New York, black locust established 97 stems/acre (240 stems/ha) in the 8- to 12-inch (20-30 cm) size class and 32 stems/acre (80 stems/ha) in the 12- to 16-inch (30-40 cm) size class in 20 to 40 years. Black locust also dominated the seedling and sapling layer of a mixed-oak dry forest, occurring at a density of 898 stems/acre (2,220 stems/ha) in the 0- to 1-inch (0-2.5 cm) size class . In a pine barrens community near Albany, New York, black locust occurred in nearly pure patches covering 1.2 to 12 acres (0.5-5 ha); these patches were surrounded by pitch pine and scrub oak . In restored oak savanna and woodland sites in Minnesota, black locust stem densities ranged from 4 to 400 stems/acre (10-1,000 stems/ha), with some areas completely dominated by black locust (Kruger personal communication cited in a review ).
Black locust seeds require scarification (, reviews by [167,181]) and bare mineral soil ([164,216], review by ) for successful germination. Though one source cites germination rates as high as 68% in its native range , most sources suggest that seed germination is low (review by ) due to high seed coat impermeability (, review by ) and shade intolerance [164,252]. Direct-seeded black locust on limestone and acid-shale sites in Ohio had low germination rates, ranging from 3% to 17%. Survival of these germinants ranged from 23% to 78% . Fifteen to 33 days after planting in a greenhouse, fall-collected black locust seeds from New Haven, Connecticut, exhibited 45% germination. The addition of various salt concentrations delayed and slightly lowered percent germination .
In greenhouse trials, black locust seeds germinated uniformly over a 5-week period .
Black locust seeds may persist in the soil for long periods of time. A Michigan flora states that seeds may survive for more than 88 years in the soil . In a laboratory study, seed from 107 plant species was buried up to 42 inches (107 cm) in soil. Black locust was 1 of 16 plant species with more than 15% of seeds viable after 39 years . Other sources state that seeds remain viable for more than 10 years (, review by ) or "many" years [87,113]. In mixed-oak and northern hardwood forests of western North Carolina, black locust seeds remained viable in the soil for more than 1 year. Soil seed densities were higher than seed rain, suggesting low annual seed mortality and the presence of seeds from previous years .
Because black locust seeds are persistent, they may accumulate to great levels in the seed bank. In Hungary, seeds accumulated over decades in the top 4 inches (10 cm) of soil (review by ). In a second-growth mixed-hardwood forest in Great Smoky Mountains National Park, black locust seeds were found in the soil at a density of 29,817 seeds/acre (73,680 seeds/ha) . In contrast, in a mature mixed-oak-maple forest in southwest Virginia, black locust seeds were found at a density of only 121 seeds/acre (300 seeds/ha). The authors suggested that the continuous cover of mature forest would make it difficult for early-successional species like black locust to produce a large quantity of seeds .
Large size causes most black locust seeds to fall near the parent plant (review by ), and black locust is generally considered to have a low dispersal rate . However, long-distance dispersal is possible; black locust recruited by seed onto a revegetating landfill site on Staten Island, New York. The closest seed source was 397 feet (121 m) from the landfill .
Pollination and breeding system
Growth Form (according to Raunkiær Life-form classification)
More info for the terms: geophyte, phanerophyte
Raunkiaer  life form:
Reaction to Competition
Except for reclamation, most forest managers consider this tree a weed species and a strong competitor against more desirable species. Two years after clearcutting a mixed hardwood stand from a good site on the southern Cumberland Plateau, 28 percent of all woody stems taller than 1.4 in (4.5 ft) were black locust. Ten years after clearcutting a high-quality hardwood stand in the southern Appalachians, the number of free-to-grow black locust had decreased but it was still the most abundant tree species (28). Dense black locust thickets occupied at least 15 percent of the area and suppressed the growth of more desirable species (4). Frill treatment with 2,4,5-T controlled the thickets. Glyphosate effectively controlled black locust in Christmas tree plantations in Maryland (17).
Life History and Behavior
In its nonnative range, flowering occurs mostly from May to June in the Pacific Northwest , California , the Southwest , Northeast and Canada , and Great Plains [128,313]. Earlier flowering occurs from March to May in north-central Texas , while later flowering occurs in some parts of New England, extending into July . In the uplands of the Adirondacks, flowering generally occurs only in June .
Fruit begins ripening as early as July in the Carolinas  or August in Arkansas , and ripening extends into November [165,261]. In the Southwest, fruit ripens from September to October . Black locust seeds persist through the winter [113,165], though dispersal is described as occurring from September to April in both its native (review by ) and nonnative  ranges.
Biology and Spread
Black locust reproduces vigorously by root suckering and stump sprouting to form groves (or clones) of trees interconnected by a common fibrous root system. Physical damage to roots and stems increases suckering and sprouting, making control difficult. Black locust clones easily spread in quality and restorable natural areas. Although black locust produces abundant seeds, they seldom germinate.
During seedling development, the first leaf appears within a week after germination and is 8 to 10 cm (3 to 4 in) long after 2 months. The young stems are zig-zag, round to slightly angular, and in the latter half of the first year develop pairs of thorns from stipules at the base of leaf petioles (29). Black locust seedlings grow rapidly when planted on good sites and competition is sparse. Control of competition aids in the establishment and growth of seedlings because black locust is intolerant of shade and herbaceous competition. In plantations in the Tennessee Valley, it was a very site-exacting species and grew poorly on severely eroded sites (1). Average annual height growth of 5-year-old plantations ranged from 0.3 m (1.1 ft) on severely sheet-eroded sites to 0.8 m (2.6 ft) on sites with little or no erosion. In the Central States, annual height growth for the first 10 years averaged 0.5 m (1.5 ft) on below-average sites but was 1.2 m (4 ft) or more on good sites (37). Black locust can be established on poor and disturbed sites. It has been widely planted for erosion control along roadsides and for reclamation of surface mine spoil banks. Throughout the Eastern and Central States, reclamation plantings have been successful across a wide range of spoil bank conditions.
Flowering and Fruiting
Growth and Yield
Young trees grow very fast on good sites, but the species matures early and growth rate decreases rapidly after 30 years, especially on poor sites (table 1). Sprouts grow more rapidly than seedlings. Average yields from 27-year-old plantations in the Central States were 126 m³/ha (1,800 ft³/acre, 1,100 posts/acre, or 4,100 bd.ft./acre). On the best sites, black locust requires 15 to 20 years to produce post-size trees and 30 years to produce 20 cm (8 in) bolts (37). Little information is available on the growth and yield of black locust in natural stands, but numerous studies have documented its early growth in reclamation plantings (5,7,11,20,37). In West Virginia, slope percent, aspect, elevation, and extent of regrading accounted for 60 percent of height growth variation. Estimated annual height growth on surface-mined sites was tabulated (8).
Table 1- Average size of plantation-grown black locust in the Central States (37) Site index at basde age 50 years Plantation
Age 9.1 m or 30 ft 18.3 m or 60 ft 27.4 or 90 ft D.b.h. Height D.b.h. Height D.b.h. Height yr cm m cm m cm m 10 4 3.7 7 8.2 11 12.8 25 10 7.6 15 14 21 20.7 40 -- 9.1 -- 17.7 27 25.6 yr in ft in ft in ft 10 1.6 12 2.8 27 4.4 42 25 4.1 25 6 46 8.4 68 40 -- 30 -- 58 10.8 84 Early growth information is available for black locust plantations on abandoned fields in the Arkansas Ozarks (32). On the best 11-year-old plantations, heights ranged from 7.8 to 11.5 m (25.7 to 37.8 ft) and diameters ranged from 6.9 to 10.4 cm (2.7 to 4.1 in). Many of the plantations were complete failures, and established plantations were often severely damaged by insects.
Molecular Biology and Genetics
Selection and propagation of trees with superior vigor, form, and resistance to borers have been attempted. The most promising selections were tested in several States. Early results indicate significant differences in borer attack between clones and between sites; however, differences were small and may have no practical application (33).
Four hybrids are recognized (27). These are crosses with Kelsey locust, Robinia kelseyi Hutch. (R. x slavinii Rehd.); New Mexico locust, R. neomexicana Gray (R. x holtii Beissn.); clammy locust, R. viscosa Vent. (R. x ambigua Poir.); and bristly locust, R. hispida L. (R. x margaretta Ashe).
Barcode data: Robinia pseudoacacia
Statistics of barcoding coverage: Robinia pseudoacacia
Public Records: 8
Specimens with Barcodes: 21
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Pests and potential problems
There are 2 primary insects inflicting damage on black locust: locust leaf miner and black locust borer. The leaf miner attacks the tree in spring, turning the leaves brown by mid-summer or early fall. Overall tree growth is impacted, but not seriously. The larvae
of the locust borer carve tunnels through the trunk of the tree, weakening it enough for wind breakage. Planting on good quality sites or in conjunction with other hardwood species and shading trunks will discourage infestation by locust borers. Heart rot is the only noteworthy disease effecting black locust.
Please contact your local agricultural extension specialist or county weed specialist to learn what works best in your area and how to use it safely. Always read label and safety instructions for each control method. Trade names and control measures appear in this document only to provide specific information. USDA, NRCS does not guarantee or warranty the products and control methods named, and other products may be equally effective.
Cultivars, improved and selected materials (and area of origin)
Ornamental varieties have been developed which are available from commercial nurseries. The Steiner group black locust was selected and released by the NRCS Plant Materials Program, for critical area re-vegetation in the Appalachian region. The three cultivars in the Steiner group, 'Appalachia' (VA), 'Allegheny' (WV), and 'Algonquin' (WV) are clonally propagated.
During establishment, protection from weeds and deer are the main management priorities. Due to the rapid early growth, two years of protection are usually sufficient. Pre-plant site preparation to control weeds with tillage or herbicides is recommended, with continued weed control after planting. Where exceptional deer pressure exists, tubes or mesh sleeves may be required. Once established this species will not require active management unless straight trunks are desired for fence posts- see Pests for information about controlling locust borers.
This plant is considered noxious and/or invasive in some states. This plant may become weedy or invasive in some regions or habitats and may displace desirable vegetation if not properly managed. Please consult with your local NRCS Field Office, Cooperative Extension Service office, or state natural resource or agriculture department regarding its status and use. Weed information is also available from the PLANTS Web site at plants.usda.gov.
Relevance to Humans and Ecosystems
Other uses and values
The wood of black locust is heavy, strong, and durable [85,113,156,165,311] and shrinks little upon drying . Its strength is due to high lignin content . Consequently, the wood of black locust is valuable for a variety of uses, such as fenceposts [3,31,97,113,165,311,313,344], railroad ties ([165,313], review by ), insulator pins (, review by ), mine timbers (, review by ), shipbuilding ([3,311], review by ), furniture , handles , barrel staves (review by ), boxes and crates, pulp, and fuelwood (review by ).
Black locust has been widely planted for windbreaks and shelterbelts ([97,277], review by ), as woody biomass for energy production , and as a street or ornamental tree (, reviews by [145,167]). It has also been widely planted for honey production (, reviews by [145,167,181]). One author claims that black locust plantations provide the basis for Hungary's commercial honey industry (review by ).
The nitrogen-fixing abilities of black locust have prompted its planting in nurseries and plantations to assist the growth of other desired trees (, review by ). Black walnut , southern catalpa (Catalpa bignoides) , and hardwoods in Indiana  have shown improved growth when planted with black locust. In Canada, black walnuts interplanted with black locust had higher foliar nitrogen content than those not planted with black locust . However, the wide-spreading crown and prolific root sprouts of black locust may suppress or kill slow-developing interplanted tree seedlings in some plantation settings .
Black locust was once a favored tree for restoration or rehabilitation because its extensive root system holds and stabilizes the soil surface, it sprouts vigorously and prolifically, it increases soil fertility through nitrogen fixation , and it forms a leaf litter that protects the soil [9,180,291]. Its main use has been in the rehabilitation of former surface mine sites ([3,16,51,113,159,238,267], reviews by [167,204]) and for erosion control ([31,97,121,176,313], review by ), but it is also used to rehabilitate contaminated soils [52,267], depleted soils , gravel pits , and logged areas  and to stabilize railroad embankments (review by ) and highway edges (review by ).
In both its native and nonnative range in North America, mortality is caused by insects and disease ([117,281,303], review by ). Black locust is highly susceptible to witches' broom disease caused by the virus Chlorogenus robiniae (review by ), as well as fungal diseases leading to heart rot (, review by ). In South Carolina hardwood stands, 13.5 % of poletimber-sized and 30.4 % of sawtimber-sized black locust had hardwood cankers . In the Great Plains, black locust was susceptible to stem decay fungi; about 25% of the 40-year-old windbreak black locust planted in Oklahoma was infected with stem decay fungi (review by ).
In the United States and Canada, the most serious insect threat to black locust is the locust borer (, reviews by [26,167]). This species is often the cause of rapid population declines in plantation settings in black locust's native [27,121,281] and nonnative ranges (, review by ), and a major reason that planting black locust has fallen out of favor in the United States . An Element Stewardship Abstract for black locust suggests that rapidly growing trees more than 10 years old are not usually attacked by locust borer (review by ). However, another author states that locust borers require the furrowed bark of older trees for egg laying. Consequently, young trees with smooth bark are not impacted . On mined sites in Illinois, planted black locust declines attributed to the locust borer were seen within 15 years of planting, and after 60 years, all black locust were dead . In a dense, early-successional black locust stand in western North Carolina, 21% of the black locust stems were standing dead, and 18% had greater than 50% crown dieback, primarily from damage by the locust borer . Locust borer infestations not only cause mortality, but may inhibit growth (, review by ) and reproduction . Locust borer infestations may be higher when trees are stressed due to poor soils (, review by ) or dense stand conditions .
Other potential insect pests in the native range of black locust include locust leaf miners ([117,365], review by ) and the locust twig borer (review by ). Outside of its native range in the Northern Great Plains, black locust is susceptible to the carpenterworm and ash and honey-locust plant bugs (review by ). Roots of the black locust are parasitized by root-knot and root-lesion nematodes in nurseries in the Northern Great Plains (, review by ).
A lack of mortality-inducing insects or diseases outside of North America is one reason black locust plantations remain popular throughout the world. In 1980, there were approximately 2.5 million acres (1 million ha) of planted black locust across the globe (review by ).
Importance to Livestock and Wildlife
Though often considered poisonous to livestock, black locust is grown in some areas specifically as livestock forage. Black locust provides food and structural habitat for a variety of wildlife species.
Palatability and/or nutritional value: Numerous accounts describe parts of the black locust as poisonous to livestock including mules (review by ), horses ([136,313], review by ), cattle [136,303,313], and domestic sheep (, review by ) due to the presence of the poison robotin . Poisonous plant parts include the roots , young shoots ([136,303,313], review by ), seeds [85,153,190,258,313], twigs , leaves [85,153,258], and bark ([85,113,136,153,258,313], review by ). In some cases, poisoning may be fatal to livestock ([136,153], review by ), though one author asserts that fatality from poisoning is rare . In livestock, symptoms of black locust poisoning may include reduced hearing, stupor, vomiting, and purging (review by ).
Despite the potential for black locust poisoning and its classification in one guidebook as worthless to poor forage for livestock (review by ), black locust is used as livestock feed in parts of its introduced range. It is grown to feed domestic goats in northern Pakistan , domestic sheep and goats in New Zealand [193,249], and general livestock in Bulgaria and Korea (review by ). In Mendocino County, California, chickens were observed eating black locust seeds, and horses ate the leaves sparingly . In North Carolina, domestic goats and cattle defoliated black locust shoots in an abandoned orchard. The level of browsing was substantial enough to kill all black locust after 4 years of browsing .
Black locust is a food item for many wildlife species. White-tailed deer heavily browse black locust in North Carolina, , Georgia , and Arkansas (review by ), though one study found a lack of white-tailed deer herbivory on black locust in Maryland and West Virginia . Mule deer browse black locust in Washington , California (, review by ), and New Mexico (review by ). Rabbits browse on stems (, review by ). Ruffed grouse eat black locust leaves . Squirrels (, reviews by [69,312]), doves , California quail (review by ), northern bobwhite ([110,138,170,275], review by ), chukar (review by ), pheasants (, review by ), ruffed grouse , and other game birds (, review by ) eat black locust seeds.
Invertebrate species also consume black locust. Freshly fallen black locust leaves were palatable to millipedes in laboratory studies . Black locust was a host to the Lepidopteran species the silver-spotted skipper and the three-staff underwing in the southeastern United States , and it is widely visited by bees for its nectar throughout its native and nonnative ranges (, review by ).
Nutritional content: Black locust seeds are high in crude protein ([253,258], review by ), phosphorus (, review by ), and crude fats and low in calcium (review by ). Black locust leaves had the highest nitrogen content of any tree tested in a North Carolina mixed-oak-hardwood forest . Five- to 10-year-old black locust in a western North Carolina mixed-oak and cove hardwood forest had significantly higher leaf nitrogen than the other 7 dominant species tested (P=0.0001). Along with yellow-poplar, black locust also had higher leaf potassium and phosphorus compared to other species (P=0.0001) .
Humans: Black locust is poisonous to humans [85,153,313]. In some cases, poisoning may be fatal . Symptoms of black locust poisoning include dilated pupils, feeble pulse, severe vomiting, and a death-like pallor . Humans may get dermatitis from exposure to black locust wood .
Cover value: Black locust is an important cover species for wildlife (review by ), providing nesting, roosting, and thermal cover. The persistent nature of black locust stems after plant death makes it an important resource for cavity-dependent wildlife species . A disproportionate number of snags were identified as black locust in a Maryland old-growth forest remnant , a 24- to 64-year-old yellow-poplar-red maple stands in southeast Ohio , and second- and old-growth mixed-hardwood forests in eastern Kentucky . Compared to surrounding forest, a disproportionate number of cavities were found in black locust trees in mixed-hardwood  and oak-hickory  forests in West Virginia.
Black locust cavities are used for nesting and roosting by bats and birds. Black locust cavities were used as maternity roosts for long-eared bats in West Virginia [228,248] and the endangered Indiana bat in the Champlain Valley , and as day roosts for male northern bats in West Virginia . In its native range, black locust provides nesting cavities for birds such as the hairy woodpecker , downy woodpecker , northern flicker [65,219] and red-bellied woodpecker . In Kentucky, eastern screech-owls roosted in black locust cavities in the winter .
Black locust cover is also important to birds. Black locust was positively associated with red-eyed vireo habitat in southwestern Virginia  and rufous-sided towhee habitat in Maryland . In a mixture of small deciduous woodlots and thickets interspersed with old fields in Kentucky, adult and juvenile eastern screech-owls used black locust stands for roosting in the postfledging period .
Outside of the native range of black locust, birds that nest in black locust foliage include the black-billed magpie, western kingbird, Baltimore oriole , and Swainson's hawk in eastern Washington [14,28], the long-eared owl  and loggerhead shrike in Idaho , and the dickcissel in central Oklahoma . Near Cape Cod, Massachusetts, black locust stands provided suitable cover for northern bobwhite and American woodcock . In south-central Kansas, 62 breeding bird species were detected in shelterbelts containing black locust , and black locust was highly recommended for planting as wildlife habitat in the Northern Great Plains region (review by ).
Black locust occurring in small (0.52 acre (0.21 ha)) to large (8.92 acre (3.61 ha)) patches in the Palouse prairie region of eastern Washington and northern Idaho provided winter thermal, loafing, and hiding cover for 7 mammal species (moose, white-tail deer, coyote, North American porcupine, striped skunk, house cat, and mountain cottontail), 23 avian species (including gray partridge, ring-necked pheasant, red-tailed hawk, rough-legged hawk, great-horned owl, and short-eared owl), and 1 reptile (garter snake) .
Black locust is widely planted in the United States, Europe, and Asia for erosion control, reclamation of drastically disturbed sites, windbreaks, nurse crops, amelioration of sites, honey production, and ornamental use. Many early plantations on severely eroded old fields were failures, but establishment on spoil banks has been generally successful. Black locust is often broadcast or hydroseeded with a mixture of herbaceous seed. The most commonly used seeding rate is 2.2 to 3.4 kg/ha (2 to 3 lb/acre) (12).
Because of its soil-improving properties, black locust is often planted in mixtures. Many species have been underplanted in black locust stands. Success of such planting has been variable and many factors have to be considered carefully (37). On mine spoil in Illinois, black locust was a valuable nurse crop for black walnut (Juglans nigra), silver maple (Acer saccharinum), and yellow-poplar (Liriodendron tulipifera), but not for cottonwood (Populus deltoides), sweetgum (Liquidambar styraciflua), or Osage-orange (Maclura pomifera) (25). On surface-mined land in Kansas, survival, growth, and form of black walnut were impaired when planted with black locust (39).
Black locust was superior to other hardwoods in developing wildlife habitat on mine spoils. It quickly provided cover, and by 10 to 15 years native vegetation had established a dense undergrowth (36). Its seeds are rated low as wildlife food but are used to a limited extent by Northern bobwhite, other game birds, and squirrels (30,42). White-tailed deer browse the young growth, and a study in the southern Appalachians showed that 92 percent of the sprouts were browsed (13). Because older trees are usually infected with heart rot, woodpeckers often construct cavities in them. Nest cavities of the downy woodpecker, hairy woodpecker, and common flicker have been found (9).
Since the wood of black locust is strong, hard, and extremely durable, it is extensively utilized for fencing, mine timbers, and landscaping ties. This tree also serves as a good erosion control plant on critical and highly disturbed areas, due to its ease of establishment, rapid early growth and spread, and soil building abilities. It has limited value in wildlife food plots, but provides excellent cover when planted in spoil areas. Due to its showy aromatic flower, it has often been planted as an ornamental, but this practice should be discouraged due to the potential for spread by root suckers. This species has been planted outside its natural range, and can crowd out other plants, particularly in sandy soils.
Ecological Threat in the United States
Black locust poses a serious threat to native vegetation in dry and sand prairies, oak savannas and upland forest edges, outside of its historic North American range. Native North American prairie and savanna ecosystems have been greatly reduced in size and are now represented by endangered ecosystem fragments. Once introduced to an area, black locust expands readily into areas where their shade reduces competition from other (sun-loving) plants. Dense clones of locust 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 black locust compete with native plants for pollinating bees.
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Robinia pseudoacacia, commonly known as the 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.
With a trunk up to 0.8 m diameter (exceptionally up to 52 m tall and 1.6 m diameter in very old trees), with thick, deeply furrowed blackish bark. The leaves are 10–25 cm long, pinnate with 9–19 oval leaflets, 2–5 cm long and 1.5–3 cm broad. Each leaf usually has a pair of short spines at the base, 1–2 mm long or absent on adult crown shoots, up to 2 cm long on vigorous young plants. The intensely fragrant (reminiscent of orange blossoms) flowers are white to lavender or purple, borne in pendulous racemes 8–20 cm long, and are edible. The fruit is a legume 5–10 cm long, containing 4–10 seeds.
Although similar in general appearance to the honey locust, it lacks that tree’s characteristic long branched thorns on the trunk, instead having the pairs of short spines at the base of each leaf; the leaflets are also much broader.
The black locust is native in the United States from Pennsylvania to northern Georgia and westward as far as Arkansas and Oklahoma, but has been widely spread. The tree reaches a height of seventy feet, with a trunk three or four feet in diameter and brittle branches that form an oblong narrow head. It spreads by underground shoots. The leaflets fold together in wet weather and at night; some change of position at night is a habit of the entire leguminous family.
- Bark: Dark gray brown tinged with red, deeply furrowed, surface inclined to scale. Branchlets at first coated with white silvery down. This soon disappears and they become pale green, afterward reddish brown. Prickles develop from stipules, are short, somewhat triangular, dilated at base, sharp, dark purple, adhering only to the bark, but persistent.
- Wood: Pale yellowish brown; heavy, hard, strong, close-grained and very durable in contact with the ground. The wood has a specific gravity 0.7333, and a weight of approximately 45.7 pounds per cubic foot.
- Winter buds: Minute, naked, three or four together, protected in a depression by a scale-like covering lined on the inner surface with a thick coat of tomentum and opening in early spring; when forming are covered by the swollen base of the petiole.
- Leaves: Parallel, compound, odd-pinnate, 21-40 inches long, with slender hairy petioles, grooved and swollen at the base. Leaflets petiolate, seven to nine, one to two inches long, one-half to three-fourths of an inch broad, emarginate or rounded at apex. They come out of the bud conduplicate, yellow green, covered with silvery down which soon disappears; when full grown are dull dark green above, paler beneath. Feather-veined, midvein prominent. In autumn they turn a clear pale yellow. Leafs out relatively late in spring. Stipules linear, downy, membranous at first, ultimately developing into hard woody prickles, straight or slightly curved. Each leaflet has a minute stipel which quickly falls and a short petiole.
- Flowers: May or June, after the leaves. Papilionaceous. Perfect, borne in loose drooping racemes four to five inches long, cream-white, about an inch long, nectar bearing, fragrant. Pedicels slender, half an inch long, dark red or reddish green.
- Calyx: Campanulate, gibbous, hairy, five-toothed, slightly two-lipped, dark green blotched with red, especially on the upper side teeth valvate in bud.
- Corolla: Imperfectly papilionaceous, petals inserted upon a tubular disk; standard white with pale yellow blotch; wings white, oblong-falcate; keel petals incurved, obtuse, united below.
- Stamens: Ten, inserted, with the petals, diadelphous, nine inferior, united into a tube which is cleft on the upper side, superior one free at the base. Anthers two-celled, cells opening longitudinally.
- Pistil: Ovary superior, linear-oblong, stipitate, one-celled; style inflexed, long, slender, bearded; stigma capitate; ovules several, two-ranked.
- Fruit: legume two-valved, smooth three to four inches long and half an inch broad, usually four to eight seeded. Ripens late in autumn and hangs on the branches until early spring. Seeds dark orange brown with irregular markings. Cotyledons oval, fleshy.
Black locust is a major honey plant in the eastern US, and, having been taken and planted in France, Italy and other European nations. At least In France and Italy it is the source of the renowned acacia monofloral honey. Flowering starts after 140 growing degree days. However, its blooming period is short (about 10 days) and it does not consistently produce a honey crop year after year. Weather conditions can have quite an effect on the amount of nectar collected as well; in Ohio state for example, good locust honey flow happens in one out of five years.
In Europe it is often planted alongside streets and in parks, especially in large cities, because it tolerates pollution well. The species is unsuitable for small gardens due to its large size and rapid growth, but the cultivar ‘Frisia’, a selection with bright yellow-green leaves, is occasionally planted as an ornamental tree.
In 1900 it was reported that the value of Robinia pseudoacacia was practically destroyed in nearly all parts of the United States beyond the mountain forests which are its home by locust borers which riddle the trunk and branches. Were it not for these insects, it would be one of the most valuable timber trees that could be planted in the northern and middle states. Young trees grow quickly and vigorously for a number of years, but soon become stunted and diseased, and rarely live long enough to attain any commercial value.
Black locust leaves contain flavone glycosides characterised by spectroscopic and chemical methods as the 7-O-β-d-glucuronopyranosyl-(1 → 2)[α-l-rhamnopyranosyl-(1 → 6)]-β-d-glucopyranosides of acacetin (5,7-dihydroxy-4′-methoxyflavone), apigenin (5,7,4′-trihydroxyflavone), diosmetin (5,7,3′-trihydroxy-4′-methoxyflavone) and luteolin (5,7,3′,4′-tetrahydroxyflavone).
The wood is extremely hard, resistant to rot and durable, making it prized for furniture, flooring, paneling, fence posts and small watercraft. Wet, newly-cut planks have an offensive odour which disappears with seasoning. As a young man, Abraham Lincoln spent much of his time splitting rails and fence posts from black locust logs. Black locust is still in use in rustic handrail systems. Flavonoids in the heartwood allow the wood to last over 100 years in soil. In the Netherlands and some other parts of Europe, black locust is one of the most rot-resistant local trees, and projects have started to limit the use of tropical wood by promoting this tree and creating plantations. It is one of the heaviest and hardest woods in North America.
Black locust is highly valued as firewood for wood-burning stoves; it burns slowly, with little visible flame or smoke, and has a higher heat content than any other species that grows widely in the Eastern United States, comparable to the heat content of anthracite. It is most easily ignited by insertion into a hot stove with an established coal bed. For best results it should be seasoned like any other hardwood, however black locust is also popular because of its ability to burn even when wet. In fireplaces it can be less satisfactory because knots and beetle damage make the wood prone “spitting” coals for distances of up to several feet. If the black locust is cut, split, and cured while relatively young (within ten years), thus minimizing beetle damage, “spitting” problems are minimal.
It is also planted for firewood because it grows rapidly, is highly resilient in a variety of soils, and it grows back even faster from its stump after harvest by using the existing root system. (see coppicing)
With fertilizer prices rising, the importance of black locust as a nitrogen-fixing species is also noteworthy. The mass application of fertilizers in agriculture and forestry is increasingly expensive; therefore nitrogen-fixing tree and shrub species are gaining importance in managed forestry.
Black locust’s pods are small and light, and easily carried long distances. Although the bark and leaves are toxic, various reports suggest that the seeds and the young pods of the black locust are edible. Shelled seeds are safe to harvest from summer through fall, and are edible both raw and/or boiled. Due to the small nature of Black Locust seeds, shelling them efficiently can prove tedious and difficult. In France and in Italy Robinia pseudoacacia flowers are eaten as beignets after being coated in batter and fried in oil.  Important constituents of the plant are the toxalbumin robin, which loses its toxicity when heated and robinin, a non-toxic glucoside. Horses that consume the plant show signs of anorexia, depression, incontinence, colic, weakness, and cardiac arrhythmia. Symptoms usually occur about 1 hour following consumption, and immediate veterinary attention is required.
The name locust is said to have been given to Robinia by Jesuit missionaries, who fancied that this was the tree that supported St. John in the wilderness, but it is native only to North America. The locust tree of Spain (Ceratonia siliqua or Carob Tree), which is also native to Syria and the entire Mediterranean basin, is supposed to be the true locust of the New Testament.
Robinia is now a North American genus, but traces of it are found in the Eocene and Miocene rocks of Europe.
Names and Taxonomy
Black locust hybridizes with Kelsey locust (R. kelseyi), New Mexico locust (R. neomexicana), clammy locust (R. viscosa), and bristly locust (R. hispida) (reviews by [167,203]). Several black locust cultivars are available .