Black Locust (Robinia pseudoacacia)

Black Locust (Robinia pseudoacacia)

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Common Name(s): Black Locust, Robinia, False Acacia

Scientific Name: Robinia pseudoacacia

Distribution: Central-eastern United States (also widely naturalized in many temperate areas worldwide)

Tree Size: 100 ft (30 m) tall, 3 ft (1 m) trunk diameter

Average Dried Weight: 48 lbs/ft3 (770 kg/m3)

Specific Gravity (Basic, 12% MC): .66, .77

Janka Hardness: 1,700 lbf (7,560 N)

Modulus of Rupture: 19,400 lbf/in2 (133.8 MPa)

Elastic Modulus: 2,050,000 lbf/in2 (14.14 GPa)

Crushing Strength: 10,200 lbf/in2 (70.3 MPa)

Shrinkage: Radial: 4.6%, Tangential: 7.2%, Volumetric: 10.2%, T/R Ratio: 1.6

Color/Appearance: Color can range from a pale greenish-yellow to a darker brown. Tends to darken to a russet brown with age. Can be confused with Osage Orange and Honey Locust in some instances.

Grain/Texture: Grain is usually straight, with a medium texture.

Endgrain: Ring-porous; large earlywood pores 2-3 pores wide, small latewood pores in clusters and tangential bands; tyloses extremely abundant; growth rings distinct; rays barely visible without lens; parenchyma vasicentric, aliform, and confluent.

Rot Resistance: Rated as very durable in regard to decay resistance, with good weathering characteristics. Frequently used as fence posts for its outdoor longevity.

Workability: Overall working characteristics for Black Locust are mixed: although the grain is usually straight, its high density and hardness can make it difficult to machine. Black Locust also has a moderate blunting effect on cutting edges. Responds very well to both lathe turning and steam bending; glues and finishes well.

Odor: No characteristic odor.

Allergies/Toxicity: Although severe reactions are quite uncommon, Black Locust has been reported to cause eye and skin irritation. Another (uncommon) side effect reported is nausea. See the articles Wood Allergies and Toxicity and Wood Dust Safety for more information.

Pricing/Availability: Black Locust prices can vary depending on location, but prices should be moderate within its natural range. Those living in the eastern United States can expect prices to be comparable to White Oak. In other areas where the lumber has been imported, the prices can be much higher.

Sustainability: This wood species is not listed in the CITES Appendices, and is reported by the IUCN as being a species of least concern.

Common Uses: Fence posts, boatbuilding, flooring, furniture, mine timbers, railroad ties, turned objects, and veneer.

Comments: Black Locust is a very hard and strong wood, competing with Hickory (Carya genus) as the strongest and stiffest domestic timber: but with more stability and rot resistance.

Although it shares a similar common name with Honey Locust, the two aren’t in the same genus, (Robinia and Gleditsia, respectively). Black Locust tends to be slightly heavier, harder, and with more of a green or yellow tinge, while Honey Locust tends to have a warmer orange or red tint.

Related Species:

None available.

Related Articles:

Scans/Pictures: A special thanks to Steve Earis for providing the wood sample of this wood species.

Black Locust (Robinia pseudoacacia)

Black Locust (sanded)

Black Locust (sealed)

Black Locust (sealed)

Black Locust (endgrain)

Black Locust (endgrain)

Black Locust (endgrain 10x)

Black Locust (endgrain 10x)

Black Locust: fluorescence (under blacklight)

Black Locust: fluorescence (under blacklight)