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Robinia pseudoacacia L.

Black locust, False acacia

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Toxicity
  5. Description
  6. Germplasm
  7. Distribution
  8. Ecology
  9. Cultivation
  10. Harvesting
  11. Yields and Economics
  12. Energy
  13. Biotic Factors
  14. Chemical Analysis of Biomass Fuels
  15. References


According to Grieve (1931), this is "one of the most valuable timber trees of the American forest, where it grows to a very large size." It was one of the first trees introduced into England from America, and is cultivated as an ornamental tree in the milder parts of Britain. It is great for posts, but one of the hardest of American wood and very difficult to work (640–800 kg/m, 15% moisture). Amerindians and Asian Indians report that the seeds are edible. Watt and Breyer-Brandwijk (1962) suggest that the seeds left in fruits hanging on the trees may still be edible, after processing. Frankly I am reluctant to experiment with this as a food source. Robinia, dangerous as it is, can serve as a vegetable rennet. The essential oil from the flowers has been used as a spice, in sherberts and toilet waters. Wood is suitable for agricultural implements, tool handles, shoe lasts, sports goods, dowels and pins for insulators on telephone and telegraph wires, tree nails, boat ribs, brackets, sleepers, and sills. It is used also for light construction, gates, wagon hubs, cart wheels, shipbuilding, furniture and turnery work. Some burrs of the trees provide attractive wood for tabletops, and music cabinets. Robinetin is a strong dyestuff yielding with different mordants different shades similar to those obtained with fisetin, quercetin, and myricetin; with aluminum mordant, it dyes cotton to a brown-orange shade (C.S.I.R., 1948–1976).

Folk Medicine

Reported to be astringent, cholagogue, diuretic, emetic, emollient, laxative, POISON, protisticidal, purgative, sedative, tonic, and vircidal, black locust is a folk remedy for dyspepsia and spasms (Duke and Wain, 1981). Cherokee used the plant as an emetic and for toothache.


Per 100 g, the seed is reported to contain 17.0–25.5 g protein, 3.0–3.3 g fat, 35.0–46.5 g NFE, 17.2–39.0 g fiber, 6.1–7.5 g ash, 1290–1500 mg Ca, 0.26–0.32 mg P. The predominant flavonoids in the heartwood are dihydrorobinetin (17.6%), robinetin (3,3',4',5',7-pentahydroxyflavone, 8%), 7,3',4',5'-tetrahydroxyflavan-3,4-diol (6.2%), and robtin (1.5%). Other flavonoids present in the heartwood are liquiritigenin, robtein, fustin, butin, butein, fisetin, 7,3',4'-trihydroxyflavan-3,4-diol, and 2',4',4-trihydroxy chalkone. Bark, leaves, and roots are reported to be toxic due to the presence of a toxal-bumin, robin (1.6% in the bark). Toxic symptoms are suggestive of those associated with belladonna poisoning. Bark also contains a glucoside robinitin (3%), syringin, tannin (up to ca 7.0%), some coloring matter and an unidentified, unstable alkaloid. Inner bark is reported to contain amygdalin, and urease. Leaves, considered antispasmodic and laxative, prescribed in digestive disorders, are poisonous to chicken. Leaves contain a coloring matter acacetin (apigenin-4'-methyl ether). Apigenin-7-bioside, apigenin-7-trioside, and indican, have also been reported. Leaves contain a volatile oil (0.01%) and carotene (209 mg/100 g). Hexene-3-ol (1) and trans-2-hexenal have been identified in the oil, the latter toxic to ciliates, such as Paramoecium. Flowers are powerfully diuretic due to the glycoside, robinin (kaempferol-7-1-rhamnosido-3'-robinobioside, 4.4%). Flowers also contain 1-asparagine a volatile oil and wax. The oil contains methyl anthranilate, linalool, a-terpineol, benzaldehyde, benzylalcohol, farnesol, heliotropin, indole, an aldehyde or ketone having a peach-like odor, and traces of pyridine-like bases. Seeds contain: moisture, 10.3–11.5; crude protein, 38.8–39.5; fat, 10.2–11.0; N-free extract, 20.4–23.0; crude fiber, 12.9–13.6; ash, 4.0–4.7; calcium (CaO), 0.19; and phosphorus (P2O5), 1.65%. Seeds contain the sugars sucrose, raffinose (traces) and stachyose, and the amino acids arginine and glutamic acid, and canavanine. Roots are rich in asparagine and are also reported to contain robin (C.S.I.R., 1946–1978).


Occasional cases of poisoning are on record in which boys have chewed the bark and swallowed the juice: the principal symptoms being dryness of the throat, burning pain in the abdomen, dilation of the pupils, vertigo, and muscular twitches; excessive quantities causing also weak and irregular heart action (Grieve, 1931). Resistance to rot may be due to the wood containing 4% taxifolin, an isomer of dihydroquercetin, or dihydrorobinetin, a growth-inhibitor of wood-destroying fungi. The flower is said to contain the antitumor compound benzoaldehyde. Some have classified the honey as toxic, others as the best of honeys (Shah, 1972).


Tree to 30 m tall, 1 m or more in diameter; bark thick, deeply furrowed, the outer bark gray, the inner yellow. Twigs brown and glabrous, usually with nodal thorns representing modified stipules; buds minute. Leaves 2–3.5 dm long, with 9–19 stalked, oval or ovate leaflets 2.5–5 cm long, 1.25–2 cm wide; glabrous, margins entire; bases rounded; tips truncate to rounded and mucronate; petioles 1–3.5 cm long, glabrous. Racemes 0.7–2 dm long, bearing many fragrant, creamy white flowers. Flowers 1.5–2.3 cm long. Pods brown, flat 5–10 cm long, 10–12 mm wide, glabrous, 4–7-seeded, finally splitting into 2 wind-carried valves with seeds attached (Brown and Brown, 1972). Seed ca 53,000–80,000/kg.


Reported from North American Center of Diversity, black locust, or cvs thereof, is reported to tolerate drought, frost, high pH, limestone, low pH, poor soil, slope, stripmine spoil. The wood of var. rectissima, so called 'Long Island' or shipmast locust has greater resistance to decay and wood borers, outlasting other locust posts and stakes by 50–100%. (2n = 22)


From Pennsylvania to northern Alabama, north to southern Illinois. Ozark Mountains in Missouri, Arkansas, Oklahoma. Now naturalized widely east of Rocky Mountains (Ag. Handbook 450). Widely introduced in the temperate and sub-temperate zones of the world, perhaps with weed potential. In southeastern Ohio, root suckers encroached on farmland at rates of ca 1–3 m/yr.


Ranging from Cool Temperate Moist to Wet through Subtropical Dry to Moist Forest Life Zones, black locust is reported to tolerate annual precipitation of 6.1 to 19.1 dm (mean of 6 cases = 11.2), annual temperature of 7.6 to 20.3°C (mean of 6 cases = 13.0), and pH of (4.6) 6.0 to 7.0 (8.2) (mean of 6 cases = 6.6). (Duke, 1978, 1979)


Scarified seed may be drilled in rows 15–20 cm apart at 65–100 seeds per meter, or broadcast in fertile soil (Mar–May; US) and covered with ca I cm or less soil, sand, or sand and sawdust. If beds have been fumigated, inoculation may be advisable. Well-drained deep soils with adequate moisture are recommended. In dry areas, in India, sowings are in sunken beds, but in wet areas, raised beds are used. The one-year old seedlings, which may attain I m, are transplanted in nurseries at 225 x 225 cm for outplanting at ca 2.4 by 2.4 m apart in wet climates. Rainy periods are avoided for plantings because they tend to encourage damping off.


Posts and fuels may be harvested as needed, once the proper size is attained. In India, 5 year old trees, on good sites, were nearly 10 m tall, 17 cm in diameter, on bad sites, nearly 3 m tall, 7 cm in diameter. On good sites, 10 year old trees were 32 cm DBH, nearly 12 m tall; on poor sites, 8 cm DBH, ca 4 cm tall. Ag Handbook 271 suggests 15–20 years to produce post-size trees.

Yields and Economics

Growth is rapid in early years, but slows down after ca 30 years. In India, a 25 year old plantation in the Simla Hills (Jutogh) gave 140 m3 stacked. Well grown 44 year old trees in the Kashmir gave 4–8 m3 of which 0.7 m3 was timber. According to Ag. Handbook 271, "The average yields for 22 plantations 27 years of age in the Central States was 1,800 cubic feet of wood per acre. This was equivalent to 1,100 posts or 4,100 board feet per acre. In 1960, only ca 7,000 m3 timber were used in the US, 70% in lumber and wood productivity, the rest in household furniture. Individual bee colonies have produced an attractive surplus of 34.5 kg honey in Kashmir, besides providing a nucleus colony. Robinia honey only contains 20.2% moisture, unprocessed (Shah, 1972). In the Danube basin, "acacia" honey commands a higher price than other honey types.


The wood is used as fuel, but I personally have been trying to burn back a stump for more than 5 years. Nonetheless, Shah (1972) characterizes it as "a very good source of firewood." Ag Handbook 271 suggests that litter decomposition releases soluble nitrates at the rate of ca 67 kg/ha under solid stands, more than twice the amount of N turnover in other forest types. N increases totaling 670 kg/ha occurred in the top 50 cm soil under 16–20 year old stands, although there was no increase under stands 5–10 years old.

Biotic Factors

An important honey tree, the nectar secretion peaking around 26–27°C. Nonpromiscuity of Robinia spp. to nodulation by heterologous strains, and, similarly noninfectiveness of locust rhizobia for other species have been repeatedly demonstrated. One rhizobial strain, for Caragana produced nodules on black locust, but the response was not reciprocal (Allen and Allen, 1981). Browne (1968) lists: Fungi. Armillaria mellea, Camarosporium robiniae, Cerrena unicolor, Cucurbitaria elongata, Diaporthe oncostoma, Diplodia profusa, Erysiphe polygoni, Fomes fraxineus, Fomes robiniae, Fomes, robustus, Ganoderma lucidum, Gibberella baccata, Laetiporus sulphureus., Nectria cinnabarina, Oxyporus populinus, Phaseospora robiniae, Phytophthora cactorum, Phytophthora parasitica, Polyporus obtusus, Schizophyllum commune, Stereum purpureum, Thanatephorus cucumeris, Trametes trogii, Verticillum alboatrum. Angiospermae. Elytranthe colensoiiscum, Viscum album. Acarina. Tetranychus telarius. Coleoptera. Cerambyx cerdo, Dereodus pollinosus, Leperisinus varius, Megacyllene robiniae, Mesosa nebulosa, Odontota dorsal. Hemiptera. Parthenolecanium corni, Quadraspidiotus perniciosus. Hymenoptera. Nematus tibialis. Lepidoptera. Alsophila pometaria, Cacoecimorpha pronubana, Datana integerrima, Epargyrecus clarus, Halysidota caryae, Halysidota maculata, Prionoxystus robiniae. Mammalia. Bos taurus, Erethizon dorsatum, Lepus europaeus, Microtis agrestis, Sciurus carolinensis. Agriculture Handbook No. 165 lists the following diseases: Aglaospora anomia (twig blight), Alternaria sp. (seedling leaf blight), Armillaria mellea (root rot), Botryosphaeria ribis, Cladosporium epiphyllum (leaf spot), Coryneum timerum, Cryptosporium robiniae, Cucurbitaria elongata, Cuscuta arvensis (dodder), Cylindrosporium solitarium (leaf spot), Cytospora coccinea, Cytospora leucosperma, Daedalea unicolor (wood rot), Diaporthe oncostoma (canker, dieback), Dothiorella glandulosa (on branches), Erysiphe polygoni (powdery mildew), Fomes applanatus (white-mottled heart rot), Fomes igniarius (white spongy heart rot), Fomes rimosus (yellow spongy heart rot), Fusarium avenaceum (on twigs), Fusarium sarcochroum (twig canker), Fusicladium robiniae (seedling leaf blight), Gibberella baccata (on twigs), Gloeosporium revolutum (leaf spot), Herpotrichia lanuginosa (on decaying wood), Heterosporium robiniae (on leaves), Macrophoma numerosa (on branches), Melanconium viscosum (on dead branches), Microsphaera diffusa (powdery mildew), Nectaria cinnabarina (on branches), Nectaria coccinea, Phleospora robiniae (leaf spot), Phoradendron flavescens (mistletoe), Phoradendron flavescens var. macrophyllum, Phyllactinia corylea (powdery mildew), Pyllosticta robiniae (leaf spot), Phymatotrichum omnivorum (root rot), Physalospora obtuse (on branches), Phytophthora cinnamomi (seedling root rot), Phytophthora parasitica (seedling top wilt), Polyporus biformis, Polyporus gilvus, Polyporus obtusus, Polyporus units, Polyporus robiniophilus (white spongy heart rot), Polyporus sulphureus (brown cubical heart rot), Poria ambigua, Poria ferruginosa,Poria incrassata (on posts—widespread), Poria robustus, Poria umbrina, Pratylenchus sp. (root nematode), Pythium myriotylum (seedling root rot), Rhabdospora breviuscula (on branches), Rhizoctonia bataticola (seedling stem rot), Rhizoctonia solani (damping-off, seedling leaf blight), Sclerotium bataticola (seedling stem rot), Septoria curvata, Sphaeropsis robiniae, Thielavia basicola (on dead roots), Tryblidiella rufula (on twigs), Verticillium alto-atrum (wilt), Xylaria longeana (wood rot), and Xylaria polymorpha (wood rot). Golden (p.c. 1984) lists Longidorus maximus, Meloidogyne sp., and Pratylenchus penetrans among the nematodes.

Chemical Analysis of Biomass Fuels

Analysing 62 kinds of biomass for heating value, Jenkins and Ebeling (1985) reported a spread of 19.71 to 18.55 MJ/kg, compared to 13.76 for weathered rice straw to 23.28 MJ/kg for prune pits. On a % DM basis, the forest residue contained 80.94 % volatiles, 0.80% ash, 18.26% fixed carbon, 50.73% C, 5.71% H, 41.93% O, 0.57% N, 0.01% S, 0.08% Cl, and undetermined residue.


Complete list of references for Duke, Handbook of Energy Crops
Last update Friday, January 9, 1998 by aw