Black Locust

Robinia is a genus of about 10 species native to eastern North America and Mexico. The genus robinia is named for Jean Robin (1550-1629) and his son Vespasian Robin (1579-1662), herbalists to kings of France and first to cultivate locust in Europe.

Robinia kelseyi Kelsey Locust
Robinia neomexicana Locust, Mexican Locust, New Mexican Locust, New Mexican Robinia, New Mexico Locust, Southwestern Locust, Thorny Locust, Western Locust
Robinia pseudoacacia* Acacia, Bastard Locust, Black Laurel, Black Locust, Common Locust, Common Robinia, False Acacia, False Black Locust, Green Locust, Honey Locust, Locust, Peaflower Locust, Post Locust, Red Locust, Robinia, Shipmast Locust, White Locust, White Honey-flower, Yellow Locust
Robinia viscosa Black Locust, Clammy-bark Locust, Clammy Locust, False Acacia, Honey Locust, Red Locust, Red-flowering Locust, Rose Acacia, Rose-flowering Locust
* commercial species

Distribution: Black Locust is native to the Appalachian Mountains from Pennsylvania to northern Georgia and Alabama and to the Ozark Mountains of southern Missouri, Arkansas and eastern Oklahoma. Also in southern Illinois and Indiana. It has been extensively naturalized in the United States and Canada.

The Tree: Black Locust reaches heights of 100 feet, with a diameter of 3 feet.

The Wood
General: The sapwood of Black Locust is a creamy white, while the heartwood varies from a greenish yellow to dark brown. It turns a reddish brown when exposed to the air. The wood is often confused with Osage Orange (Maclura pomifera). It has a high density and decay resistance. It shows slight shrinkage and stays in place well. It is very strong in bending and is one of the hardest woods in America. It's shock resistance is almost that of Hickory (Carya spp.).

Weight: (7)
MC SpGr Weight (lb/ft3) Weight (kg/m3)
Green 0.66 58 929
12 % 0.69 48 769
Oven Dry 0.71 NA NA

Mechanical Properties: (15) (2-inch standard)
Property MC English Units Metric/SI Units
MOE green 1.85 106 lb/in2 0.130 106 kg/cm2
dry 2.05 106 lb/in2 0.144 106 kg/cm2
MOR green 13.8 103 lb/in2 0.966 103 kg/cm2
dry 19.4 103 lb/in2 1.358 103 kg/cm2
C|| green 6.80 103 lb/in2 0.476 103 kg/cm2
dry 10.2 103 lb/in2 0.714 103 kg/cm2
C+ green 1.16 103 lb/in2 0.081 103 kg/cm2
dry 1.83 103 lb/in2 0.128 103 kg/cm2
Work green 15.4 in-lb/in3 0.011 kg-m/cm3
dry 18.4 in-lb/in3 0.013 kg-m/cm3
Side Hard green 1570 lb 711 kg
dry 1700 lb 770 kg
Shear|| green 1.76 103 lb/in2 0.123 103 kg/cm2
dry 2.48 103 lb/in2 0.174 103 kg/cm2

green = green moisture content
dry = 12% moisture content
MOE = Modulus of elasticity.
MOR = Modulus of rupture.
C|| = Compression parallel to grain, maximum crushing strength.
C+ = Compression perpendicular to grain, stress at proportional limit.
Work = Work to Max Load
Side Hard = Side Hardness
Shear|| = Shear parallel to grain, maximum shearing strength.

Drying & Shrinkage:
Shrinkage (% of green) GreenÆ0%MC GreenÆ6%MC GreenÆ20%MC
Tangential 7.2(15) 5.8(14) 2.4(14)
Radial 4.6(15) 3.7(14) 1.5(14)
Volumetric 10.2(15) 8.2(14) 3.4(14)

Kiln Drying Schedule (1&13)
Condition 4/4, 5/4, 6/4
stock 8/4
stock 10/4
stock 12/4
stock 16/4
stock 16/4
standard T6-A3 T3-A1 NA NA NA

Working Properties: It is difficult to work with hand tools, but turns well on a lathe and nails well. It has no distinctive odor or taste.

Durability: It is extremely durable.

Preservation: No information at this time.

Uses: Fencing, insulator pins, furniture, mine timbers, treenails for ships. The trees are used in strip mine reclamation, due to their ability to survive the acid conditions and for their nitrogen fixing roots.

Toxicity: The bark is poisonous, and there are reports of dermatitis from the wood. (4, 9, & 17)

Additional Reading & References Cited (in parentheses):
1. Boone, R.S., C.J. Kozlik, P.J. Bois & E.M. Wengert. 1988. Dry kiln schedules for commercial woods - temperate and tropical. USDA Forest Service, FPL General Technical Report FPL-GTR-57.
2. Cuno, J.B. 1930. Utilization of black locust. USDA Circular No. 131.
3. Elias, T.S. 1980. The complete trees of North America, field guide and natural history. Van Nostrand Reinhold Co., New York, 948 pp.
4. Hausen, B. M. 1981. Wood Injurious to Human Health: A Manual. Walter deGruyter & Co., Berlin, Germany; New York, NY.
5. Hopp, H. 1942. Mystery among the locusts. American Forests. Jan.:27-30.
6. Little, Jr., E.L. 1979. Checklist of United States trees (native and naturalized). USDA Forest Service, Ag. Handbook No. 541, USGPO, Washington, DC.
7. Markwardt, L.J. and T.R.C. Wilson. 1935. Strength and related properties of woods grown in the United States. USDA Forest Service, Tech. Bull. No. 479. USGPO, Washington, DC.
8. McAlister, R.H. 1971. Black locust. USDA Forest Service, American Woods - FS-244.
9. Mitchell, J.; Rook, A. 1979. Botanical Dermatology: Plants and Plant Products Injurious to the Skin. Greenglass Ltd., 691 W. 28th Ave., Vancouver, British Columbia, Canada V5H 2H4.
10. Panshin, A.J. and C. de Zeeuw. 1980. Textbook of Wood Technology, 4th Ed., McGraw-Hill Book Co., New York, 722 pp.
11. Record, S.J. and R.W. Hess. 1943. Timbers of the new world. Yale University Press, New Haven, 640 pp.
12. Scheffer, T.C. 1949. Decay resistance of black locust heartwood. USDA Technical Bulletin No. 984.
13. Simpson, W.T. 1991. Dry kiln operator's manual. USDA Forest Service, FPL Ag. Handbook 188.
14. Summitt, R. and A. Sliker. 1980. CRC handbook of materials science. Volume 4, wood. CRC Press, Inc., Boca Raton, FL. 459 pp.
15. USDA Forest Service, FPL. 1974. Wood handbook: wood as an engineering material. Ag. Handbook 72.
16. Wollerman, E.H. 1962. The locust borer. USDA Forest Service, Forest Pest Leaflet 71.
17. Woods, B.; Calnan, C. D. 1976. Toxic Woods. British Journal of Dermatology; 95(13):1-97 Published by Blackwell Scientific Publications, Oxford, England OX2 OEL.

Harry A. Alden, 1994