Robinia pseudoacacia

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).

Leguminosae -- Legume family

    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.

This tree is 40-80' tall at maturity, forming a trunk about 1½-3' across and an irregular crown with spreading to ascending branches. Trunk bark is variable, depending on the age of a tree; young trees have brown bark that is slightly rough and shallowly furrowed, while older trees have thick gray bark that is very rough and deeply furrowed with forking ridges. The bark of branches is gray to brown and more smooth, while twigs are brown to reddish brown, smooth, and glabrous with scattered white lenticels. Pairs of stout thorns about ¼-½" long occur along the twigs and branches near the axils of former leaves. Young shoots are light green and slightly pubescent. Alternate compound leaves about 6-14" long occur along the twigs and shoots; they are odd-pinnate with 7-19 leaflets. The stalks and leaflets of young compound leaves may be slightly pubescent, but they become glabrous with age; they are initially yellowish green. At maturity, individual leaflets are 1-2" long and ½-¾" across; they are medium green or blue-green, oblong or oblong-elliptic in shape, and smooth along their margins. Each leaflet has a tiny bristle-like tip, while at its base there is a short petiolule (basal stalklet) less than 1/8" long. The flowers are produced in drooping racemes about 4-6" long. The central stalk and pedicels of each raceme are pale green and glabrous to slightly pubescent. Individual flowers are ¾-1" long, consisting of 5 white petals, a tubular calyx with 5 teeth, several hidden stamens, and an ovary with a single style. The petals are arranged in a pea-like floral structure consisting of an upright banner and a pair of forward-projecting wings that enclose a keel. There is a small patch of yellow at the base of the banner. The calyx is light green, yellowish green, or pinkish green; it is either glabrous or slightly pubescent. The blooming period occurs from late spring to early summer for about 2 weeks after the leaves are fully developed. The flowers have a strong sweet fragrance. Afterwards, fertile flowers are replaced by drooping seedpods that become 2-4" long at maturity during the autumn. Mature seedpods are dark brown, oblongoid in shape, flattened, and either straight or slightly curved; each seed pod contains 4-14 seeds. The seeds are a little less than ¼" long, reniform in shape, dark brown, and somewhat flattened. They are dispersed primarily by gravity, falling to the ground not far from the mother tree. The woody root system produces lateral roots that are usually shallow and widely spreading, although at dry sites it can develop a taproot with deep lateral roots. The root system also produces long underground runners, from which clonal offsets are produced. As a result, this tree often occurs in clonal colonies. The deciduous leaves usually turn yellow during the autumn.

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

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 [167]). 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 [167]). 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 [340]).

Black Locust is occasional throughout Illinois. This tree is native to the southern tip of Illinois, otherwise it is either adventive from the south or an escape from cultivation. Habitats include upland woodlands, well-drained areas of bottomland woodlands, disturbed open woodlands, wooded slopes, savannas and sandy savannas, thickets, stabilized sand dunes, strip-mined areas, and roadsides. In Illinois, this tree is an invader of sand prairies and sandy savannas. It is also cultivated as a landscape tree in both suburban and urban settings. Because of its shade intolerance, Black Locust is more common in secondary growth woodlands than old growth forests; habitats with a history of occasional disturbance are preferred.

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.

Southeastern United States; on the lower slopes of the Appalachian Mountains, with separate outliers north along the slopes and forest edges of southern Illinois, Indiana, and Missouri

Black locust has a disjunct original range, the extent of which is  not accurately known. The eastern section is centered in the  Appalachian Mountains and ranges from central Pennsylvania and  southern Ohio, south to northeastern Alabama, northern Georgia,  and northwestern South Carolina. The western section includes the  Ozark Plateau of southern Missouri, northern Arkansas, and  northeastern Oklahoma, and the Ouachita Mountains of

    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.

Robinia pseudoacacia fo. oswaldiae Oswald:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Robinia pseudoacacia L.:
Canada (North America)
Honduras (Mesoamerica)
United States (North America)
China (Asia)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Robinia pseudoacacia var. rectissima Raber:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Robinia pringlei Rose:
Mexico (Mesoamerica)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Native of United States, cultivated and more or less naturalized in Europe and Japan.

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 locust’s invasive tendencies.

Deciduous tree, young branches glabrescent. Leaf c. 10-15 cm long, imparipinnately compound, leaflets 9-19, c. 2.0-5.5 cm long, elliptic to oval, entire, glabrescent above, puberulous at the nerves below; petiolule c. 2.5 mm long; stipels c. 1-1.5 mm long; stipules spinescent, up to 2 cm long. Inflorescence an axillary raceme, up to 20 cm long. Pedicel up to 3.8 cm long. Bract and bracteoles small, caducous. Calyx c. 5 mm long, puberulous; teeth shorter than the tube. Vexillum c. 1.5 cm long. Wing and keel subequal. Stamens 10, more or less monadelphous, anthers uniform. Ovary stipitate, style hairy and with a ring of hairs below the stigma. Fruit 10 cm or less long, c. 1.5-1.8 cm broad, glabrous.

Perennial, Trees, Woody throughout, Stems woody below, or from woody crown or caudex, Plants with rhizomes or suckers, Nodules present, Stems erect or ascending, Stems 1-2 m tall, Stems greater than 2 m tall, Trunk or stems armed with thorns, spines or prickles, Stems solid, Stems or young twigs glabrous or sparsely glabrate, Leaves alternate, Leaves petiolate, Stipules con spicuous, Stipules persistent, Stipules free, Stipules spinose or bristles, Leaves compound, Leaves odd pinnate, Leaf or leaflet margins entire, Leaflets opposite, Stipels present at base of leaflets, Leaflets 5-9, Leaflets 10-many, Leaves glabrous or nearly so, Inflorescences racemes, Inflorescence axillary, Inflorescence or flowers lax, declined or pendulous, Flowers zygomorphic, Calyx 2-lipped or 2-lobed, Calyx hairy, Petals separate, Corolla papilionaceous, Petals white, Petals ochroleucous, cream colored, Banner petal suborbicular, broadly rounded, Wing petals narrow, oblanceolate to oblong, Wing tips obtuse or rounded, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens diadelphous, 9 united, 1 free, Filaments glabrous, Style terete, Style hairy, Style hairy on one side only, Fruit a legume, Fruit unilocular, Fruit freely dehiscent, Fruit elongate, straight, Fruits winged, carinate, or samaroid, Fruit exserted from calyx, Fruit compressed between seeds, Frui t beaked, Fruit 3-10 seeded, Seeds reniform, Seed surface smooth, Seeds olive, brown, or black.

More info for the terms: association, density, mesic, reclamation, relative density, shrub, tree, xeric

The following section examines site characteristics such as general types of sites, elevation, soil characteristics, topography, and climate in black locust's native and nonnative ranges.

Native range:
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 [216], 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 [167]). It occurs below 300 feet (90 m) in parts of Kentucky [41] and Tennessee [350] and above 4,000 feet (1,200 m) in Great Smoky Mountains National Park ([45], review by [167]).

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 [2], chert [268], and mica-gneiss substrates [211]. Soils tend to be loams ([129], reviews by [167])) or sandy loams [246]. Other soil characteristics associated with black locust include "rich" ([41], reviews by [167,312]), deep ([41], review by [312]), well-drained ([2,38,129], review by [312]), and moist ([78], review by [167]) conditions.

Black locust may not grow well on very sandy, very acid, or wet soils (review by [312]). 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 [66]).

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 [211]. In the Great Smoky Mountains of Tennessee and North Carolina, black locust was found in soils with a pH of 5 [47].

Topography: Black locust is often found on slope forests within its native range ([1,2,29,211,350], review by [167]). In the Monongahela National Forest in central West Virginia, black locust occurred on slopes of 45% to 55% [2]. In the Nantahala Mountains of western North Carolina, it occurred on a 21.6° slope [211]. Black locust has been found on northwestern slopes in eastern West Virginia [1] and southerly slopes in North Carolina and Tennessee [350].

Black locust is also found on valley floors [1], bottomlands [38], floodplains [77], ridges [350], rolling uplands [41], and loess hills [40,77].

Black locust occurs in a variety of forest types in the Black and Craggy Mountains of western North Carolina, though at very low densities [222].

Relative density of black locust in xeric to mesic oak forests [222]

Forest type

Dominant species

Forest characteristics

Percent density of all trees

Mixed-oak

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

1.3

White oak

white oak, American beech, red maple

well-drained valley flats and terraces,
dry-mesic, nutrient rich, high pH

1.6

Scarlet oak

scarlet oak, red maple, sourwood

<3,400 ft, south- and west-facing ridges, slopes, and flats, dry-mesic, intermediate in nutrients and pH

2.3

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

1.5

Chestnut oak

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

1.6

Red oak

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

0.5

Relative density of black locust in mesic to wet forests [222]

Forest type

Dominant species

Forest characteristics

Percent density of all trees

Cove hardwoods

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

1.3

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

0.7

Alluvial

American sycamore, yellow birch, eastern hemlock, red maple

floodplains and terraces of large streams, mesic, moderate nutrients

0.2

Hemlock hardwoods

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

0.4

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 [167]).

Climate conditions for black locust's native range (review by [167])

  Minimum Maximum 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

Nonnative range:
General Outside of its native range, black locust thrives in disturbed ([12,91,210,231,237,272], review by [26]) 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 [144], constructed wetland edges [200], disturbed hammock margins [360], man-made sandflats [224], and channel levees [296].

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 [72]), abandoned agricultural fields [60,80,97,160,165,210,237,327,329,332] and pastures ([113,128,313], review by [72]), 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 [128], woodland openings [165], thickets [128,232], or prairies and other grasslands ([310], 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 [58], Northern Great Plains [128], Northern and Central Rockies [91,192] Northwest [17,156,198,259], Southwest (review by [307]), 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.

Elevation (feet) Location 30-350 southeastern Louisiana [77] 80-240 central Maryland [161] 160-6,300 California ([153], review by [26]) 1,000 southwestern Wisconsin [67] 3,115-3,135 Grand Canyon National Park, Arizona (review by [307]) 3,770 Las Cruces, New Mexico [185] 4,450 midwestern Himalaya of India [182] 4,500-5,500 Colorado [143,341] 4,920-7,545 southwestern New Mexico [22] 5,000-6,200 Sierra Nevada, California [295] 6,500 New Mexico (review by [302])

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 [325], the Northeast, and Canada [113]. In contrast to its native range, a strong association with sandy soils is found in the Northern Great Plains [303], north-central Texas [85], Illinois [5,133], the Northeast [236], Maryland [254], California ([296], review by [131]), and Hungary ([218], review by [181]). 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 [197], Richfield silty loam in the high plains regions of the Oklahoma panhandle [42], silty-clay loam in eastern Nebraska [301], well-drained loams in eastern Washington and northern Idaho [32], and silty or sandy loams with loose structure in Hungary (review by [181]). Clayey soils were listed as "inappropriate" in Hungary (review by [181]), and sandy or constantly wet soils were not conducive to growth in eastern Washington and northern Idaho [32].

A preference for moist sites is noted in the Northern Great Plains [313], northern United States and southern Canada [113], and Hungary (review by [181]). Black locust's deep rooting ability may allow it to grow in locations much drier than in its native range (review by [167]). 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 [224]. Several sources suggest that as in its native range, black locust does best on well-drained sites ([313,325], review by [204]). One source states that black locust prefers deep soils in the Southwest [325], though another states that it may grow well on shallow soils in the Northeast (review by [204]). Black locust is found on sites that range from low ([224], review by [204]) to intermediate [236] and high [197] 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 [272] or dry grasslands in Europe ([99], review by [340])) 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 [3]. 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 [151]. One biofuel plantation site in Las Cruces, New Mexico, had a soil pH of 7.9 [185].

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 [189]. In Ohio, black locust was most abundant on dry hillsides [31]. In California, it was locally abundant on canyon slopes [153]. In the Palouse prairie region of eastern Washington and northern Idaho, black locust occurred on hills and slopes too steep to plow [32].

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 [16]. 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 [181]).

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) [185]. 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 [272]. 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) [12].

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 [32].

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 [186]). 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 [257]). Black locust was found in southwestern Wisconsin, an area with an average annual precipitation of 30.6 inches (777.2 mm) [67], as well as in western Maine, where average annual precipitation was 44 inches (1,116 mm) [12].

Black Locust is occasional throughout Illinois. This tree is native to the southern tip of Illinois, otherwise it is either adventive from the south or an escape from cultivation. Habitats include upland woodlands, well-drained areas of bottomland woodlands, disturbed open woodlands, wooded slopes, savannas and sandy savannas, thickets, stabilized sand dunes, strip-mined areas, and roadsides. In Illinois, this tree is an invader of sand prairies and sandy savannas. It is also cultivated as a landscape tree in both suburban and urban settings. Because of its shade intolerance, Black Locust is more common in secondary growth woodlands than old growth forests; habitats with a history of occasional disturbance are preferred.

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.

Black locust grows naturally over a wide range of soils and  topography. The most common orders of soil within its native  range are Inceptisols, Ultisols, and Alfisols, and the most  common soil great groups are Hapludults, Paleudults,  Dystrochrepts, and Eutrochrepts (41). The species does best on  moist, rich, loamy soils or those of limestone origin and thrives  best on moist slopes of the eastern mountains below 1040 in  (3,400 ft) (18,21). In the Great Smoky Mountains National Park,  the upper elevational limit is 1620 ni (5,300 ft) (46). Black  locust has become established on a wide variety of disturbed  sites such as old fields or other cleared areas.

    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).

The native range of black locust is classified as humid, with two  local areas of superhumid climate (43). The range includes the  cool temperate moist forest, warm temperate montane moist forest,  warm temperate montane wet forest, and warm temperate moist  forest life zones (38).

    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.

The flowers are cross-pollinated primarily by bumblebees, although the Ruby-Throated Hummingbird, honeybees, butterflies, and moths also visit the flowers. The floral award of these visitors is nectar. According to Robertson (1929), butterflies and moths are not effective at cross-pollination, unlike the bees and hummingbird. The foliage of Black Locust is a food source for  caterpillars of the skippers Erynnis funeralis (Funereal Duskywing), Erynnis icelus (Dreamy Duskywing), Erynnis zarucco (Zarucco Duskywing), and Epargyreus clarus (Silver-Spotted Skipper). The caterpillars of several moths also feed on the foliage; they include such species as Dasylophia anguina (Black-Spotted Prominent), Euparthenos nubilis (Locust Underwing), Mellilla xanthometata (Orange Wing), Pero honestaria (Honest Pero), Sciota subcaesiella (Locust Leafroller), and Zale undularis (Black Zale). See the Moth Table for a more complete list of these species. Other insects that feed on this tree include the treehoppers Cyrtolobus fuscipennis, Hadrophallus constans, Stictocephala brevitylus dolichotylus, Telamona decorata, Thelia bimaculata, and Vanduzea arquata; the aphid Aphis cytisorum; the plant bugs Lopidea robiniae (Black Locust Plant Bug) and Orthotylus robiniae; larvae of the wood-boring beetles Agrilus egenus and Megacyllene robiniae (Locust Borer); larvae of the seed beetle Amblycerus robiniae (Locust Seed Borer) and the leaf beetle Odontota dorsalis (Locust Leafminer); larvae of Dasineura pseudoacaciae (Black Locust Gall Fly); and many others. See the Insect Table for a more complete list of these species. Notwithstanding their toxicity, the seeds are a minor food source of the Thirteen-Lined Ground Squirrel and some upland gamebirds, including the Bobwhite and Ring-Necked Pheasant. While White-Tailed Deer occasionally browse on the foliage of Black Locust without apparent ill effects, it is toxic to such domesticated animals as horses, cattle, and sheep. Because Black Locust is vulnerable to heart-rot fungi, older trees often develop cavities that become dens for bats, screech owls, and woodpeckers. Clonal colonies of Black Locust can provide significant cover for the White-Tailed Deer, Coyote, Red Fox, Striped Skunk, Ring-Necked Pheasant, Bobwhite, and other wildlife in semi-open areas.

Robinia pseudoacacia (Black Locust)
(Hummingbirds & insects suck nectar; butterflies & moths are non-pollinating; all observations are from Robertson)

Birds
Trochilidae: Archilochus colubris sn fq

Bees (long-tongued)
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

Butterflies
Nymphalidae: Danaus plexippus sn np; Papilionidae: Papilio marcellus sn np

Moths
Sphingidae: Hyles lineata sn np

Foodplant / saprobe
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

Black locust develops and grows best in cove or mixed mesophytic  forests of the central and southern Appalachian Region. These  forests are usually highly productive and characterized by a  large and variable number of species. The species is often a  component of mature forest on such sites but is seldom very  abundant. Black locust is listed as a component of the Mixed  Mesophytic Forest (6). In the Cumberland Mountains of Kentucky,  it made up about 1 percent of the mixed mesophytic forest on  north and south slopes but is considered as more properly  belonging to other communities and as a relict from preceding  stages or accidentals from nearby unlike communities. It is not  listed as a component of oak-hickory forest in the Ozark and  Ouachita Highlands or of oak-chestnut forest in the southern  Appalachians but is listed as an associate of shortleaf pine (Pinus  echinata) and Table Mountain pine (P. pungens) in the  oak-pine communities of the oak-chestnut forest region.

    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.

Black locust is severely damaged by  insects and disease, probably more than any other eastern  hardwood species. Ubiquitous attacks by the locust borer (Megcallene  robiniae) and by the heart rot fungi Phellinus rimosus  or Polyporus robiniophilus make growing black locust  for timber production impractical. Locust borer larvae construct  feeding tunnels throughout the wood, and the holes serve as entry  points for heart rot fungi that cause extensive wood decay.

    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).

More info for the terms: density, fire intensity, fire regime, fire-return interval, fuel, fuel moisture, invasive species, litter, natural, relative density, series, surface fire, total heat release

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 [9]. On the Albany Pine Bush Preserve in New York, black locust stands had a 2-fold greater litterfall mass compared to native vegetation [272]. Black locust litter decomposes quickly [9,272] and is generally moist, which may differ from the litter characteristics of native vegetation [90]. 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 [90]. 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 [83]. Some managers even consider black locust "nonflammable" [81]. In a series of laboratory trials, black locust had significantly lower combustion rates and total heat release than pitch pine (P<0.0001) [83]. 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 [90]. 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 [81]. 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.

More info for the term: reclamation

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 ([90], reviews by [167,226]) due to cutting ([108,306,365], reviews by [72,167]), fire ([108,133], review by [72]), wind, or disease (review by [72]). Root sprouting is also a common means of reproduction following logging treatments [15,363] and a means of spread into revegetating reclamation sites [139] and out of plantations and into abandoned fields [183].

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 [131]). Though sprouting is a common response to disturbance, sprouts need sufficient light to survive [35].

See Physical and/or mechanical control for more information on how black locust's regenerative abilities impact control efforts.

More info for the terms: density, hardwood, natural, reclamation, tree

Establishment: Black locust requires open conditions for establishment ([252,297], reviews by [167,314]). Establishment is often linked to natural ([37,164], review by [167]) and manmade ([99,103,285], review by [167]) 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 [167]). 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 [361]. The growth rate of black locust seedlings is limited by plant density ([120], review by [167]) and insect infestations [120,365] and enhanced by light [164], 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 [24]. 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) [364]. 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 [126]. 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 [202].

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 [167]. 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 [137]. 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 [291].

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 [2]. 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 [297].

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) [220]. 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 [260]. 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 [231]. 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 [283]).

Black locust seeds require scarification ([325], reviews by [167,181]) and bare mineral soil ([164,216], review by [314]) for successful germination. Though one source cites germination rates as high as 68% in its native range [325], most sources suggest that seed germination is low (review by [131]) due to high seed coat impermeability ([252], review by [226]) 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% [202]. 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 [19].

In greenhouse trials, black locust seeds germinated uniformly over a 5-week period [87].

More info for the terms: cover, density, hardwood, presence

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 [329]. 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 [316]. Other sources state that seeds remain viable for more than 10 years ([325], review by [26]) 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 [155].

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 [181]). 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) [118]. 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 [285].

Black locust seeds are dispersed by gravity (review by [26]), wind ([273,280], review by [26]), and potentially by birds [154,155].

Large size causes most black locust seeds to fall near the parent plant (review by [314]), and black locust is generally considered to have a low dispersal rate [87]. 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 [280].

Black locust begins producing seeds at about 6 years of age (reviews by [26,167]). Seed production is best between 15 and 40 years of age and continues through approximately age 60 (review by [167]). Seeds are produced every year, but good crops are produced at intervals of 1 to 2 (review by [167]) or 2 to 3 [113] years.

Black locust is insect pollinated [113]. Flowers are also visited by hummingbirds [165].

More info for the term: breeding system

• Pollination and breeding system
• Seed production
• Seed dispersal
• Seed banking
• Germination
• Seedling establishment and plant growth
• Vegetative regeneration

Black locust reproduces both from seed and by sprouting from the roots or stump. Sprouting is considered more common than sexual reproduction. Limited seed dispersal, seed coat impermeability, and high light requirements for germination all limit reproduction by seed.

More info on this topic.

More info for the terms: geophyte, phanerophyte

Raunkiaer [266] life form:
Phanerophyte
Geophyte

More info for the term: tree

Tree

Black locust is very sensitive to  competition and is classed as very intolerant of shade (44). It  is found in closed forest stands only as a dominant tree.  Reproduction is not successful until perturbations create  openings in which black locust, because of its rapid juvenile  growth, can compete successfully. In open areas, dense herbaceous  growth often prevents seedling establishment (37). On spoil banks  in Illinois, survival rate of planted black locust was 83  percent on sparsely vegetated sites but was only 31 percent on  densely vegetated sites (5).

    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).

Black locust ordinarily produces a shallow  and wide-spreading root system that is excellent for soil binding  but is also capable of producing deep roots. In the and  Southwest, trees may develop vertical roots from 6.1 to 7.6 m (20  to 25 ft) long (37). This deep rooting ability may explain why  black locust can grow in and lands much drier than its native  range. Radial root spread is about 1 to 1.5 times tree height   (10).

More info on this topic.

Within its native range, black locust generally flowers from April to June ([165,261,311,356], review by [167]), though one source states it may flower as early as February in the Southeast [97].

In its nonnative range, flowering occurs mostly from May to June in the Pacific Northwest [156], California [239], the Southwest [325], Northeast and Canada [123], and Great Plains [128,313]. Earlier flowering occurs from March to May in north-central Texas [85], while later flowering occurs in some parts of New England, extending into July [292]. In the uplands of the Adirondacks, flowering generally occurs only in June [190].

Fruit begins ripening as early as July in the Carolinas [261] or August in Arkansas [165], and ripening extends into November [165,261]. In the Southwest, fruit ripens from September to October [325]. 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 [167]) and nonnative [325] ranges.

Fl.Per.: March-April.

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.

Black locust sprouts readily from  both stump and roots, especially after being cut or damaged.  Although seedlings are produced, root suckers are most prevalent  in natural reproduction. Suckers usually appear in the fourth or  fifth year (37). In the southern Appalachians, dense thickets of  suckers develop in clearcuts (4,28).

Because black locust has been widely  planted, the proper seed treatment and nursery practices are well  described. Dry seeds can be stored and retain their viability for  as long as 10 years if placed in closed containers at 0° to  5° C (32° to 41° F). Because seed coats are  impermeable, germination must be induced by scarification.  Soaking in concentrated sulfuric acid, soaking in boiling or  near-boiling water, and mechanical scarification have proved  successful. Germination is epigeal (34).

    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.

Black locust begins seed production at  about age 6 and produces good crops at I- to 2-year intervals.  Seed production is best between 15 and 40 years of age and  continues until age 60. Black locust yields 7 to 15 kg (15 to 33  lb) of seeds per 45 kg (100 lb) of fruit, and seeds average  52,900/kg (24,009/lb) (34,37).

The fragrant, whitish flowers,  borne in showy racemes, appear after leaf emergence in May or  June. The perfect flowers originate in the axils of current year  leaves and are pollinated by insects, primarily bees. The fruit  is a flattened, oblong pod that ripens during September and  October. The fruit opens on the tree and seeds are dispersed from  September to April (34).

Black locust is a mediumsized tree,  generally 12 to 18 m (40 to 60 ft) in height and 30 to 76 cm (12  to 30 in) in diameter. On better sites it may reach 30 m (100 ft)  in height and 122 cm (48 in) or more in diameter. The bole of  opengrown trees is usually short and separates at 3 to 5 m (10 to  15 ft) into several stout branches, but in stands on good sites  the bole is often clear and straight (18,19).

    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.

Black locust is a variable species. Many cultural varieties have  been recognized, especially in Europe. Forty-nine varieties have  been tested in Hungary (23), and varieties have been selected  that increase wood production 18 to 32 percent and nectar  production 74 percent (31). In Korea, numerous studies have been  conducted on the development, morphology, and cytological  characteristics of spontaneous and colchicine-induced tetraploids  of black locust (24). Shipmast locust (Robinia pseudoacacia  var. rectissima), a clone of unknown origin, is  listed by Little as a natural variety (27). After protein  analysis and comparison; however, Huang and others consider  shipmast locust an ecological variant and believe that it should  not be given varietal status (22).

    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).

The following is a representative barcode sequence, the centroid of all available sequences for this species.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 8
Specimens with Barcodes: 21
Species With Barcodes: 1

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: N5 - Secure

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).

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.

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.

The preference is full sun, mesic to dry-mesic conditions, and a relatively loose soil containing loam, silty loam, or sandy loam. The root system of this tree fixes nitrogen into the soil. Black Locust develops rapidly while it is young, producing seedpods in as little as 6 years. However, it is relatively short-lived with a maximum longevity of about 90 years. 

Although black locust is not an important timber tree in the  United States, it is used for a wide variety of products and is  planted for many specialized purposes. It is used for fence  posts, mine timbers, poles, railroad ties, insulator pins, ship  timber, tree nails for wooden ship construction, boxes, crates,  pegs, stakes, and novelties. Pulp with satisfactory mechanical  properties can be made, particularly by the sulfate process (35).  It is also suitable for use in fuel plantations (14,16).

    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.

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.