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: 65-100 ft (20-30 m) tall,
2-3 ft (.6-1 m) trunk diameter
Average Dried Weight: 48.0 lbs/ft3 (770 kg/m3)
Specific Gravity (Basic, 12% MC): 0.66, 0.77
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
Grain/Texture: Grain is usually straight, with a medium texture.
Rot Resistance: Rated as very durable, 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 more difficult to machine when compared to other domestic hardwoods. 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, as well as nausea (less common). 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. Furthermore, the species has become very widespread, and is even considered invasive in some areas. Vítková, M., Müllerová, J., Sádlo, J., Pergl, J., & Pyšek, P. (2017). Black locust (Robinia pseudoacacia) beloved and despised: a story of an invasive tree in Central Europe. Forest … Continue reading
Common Uses: Fence posts, boatbuilding, flooring, furniture, mine timbers, railroad ties, turned objects, and veneer.
Although it shares a similar common name with honey locust, the two are in separate genera—Robinia and Gleditsia, respectively. (In a botanical sense, black locust trees are actually more closely related to desert ironwood (Olneya tesota), though the wood of course is less dense than ironwood.Lavin, M. (1995). Phylogenetic systematics and biogeography of the tribe Robinieae (Leguminosae). Systematic Botany Monographs, 1-165.) But when compared to honey locust, 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. For more information on separating lookalikes, see the notes on anatomy below.
Images: Drag the slider up/down to toggle between raw and finished wood. The first sample shows a piece that has already aged to a darker brown heartwood color, while the second sample is closer to the color one could expect from a freshly cut piece.
A special thanks to Steve Earis for providing a wood sample of this wood species.
Porosity: ring porous
Arrangement: earlywood in rows two to three pores wide, latewood in clusters and tangential bands
Vessels: large in earlywood, medium in latewood; tyloses abundant
Parenchyma: vasicentric and aliform
Rays: narrow to medium width; normal spacing
Lookalikes/Substitutes: Can be confused with other ring-porous hardwoods from the Eastern United States, such as honey locust, Kentucky coffeetree, osage orange, and red mulberry. However, black locust is the only species of the aforementioned group that features both abundant tyloses as well as fluorescent heartwood (when viewed under a blacklight). If a blacklight is unavailable, osage orange also features abundant tyloses and can be confused with black locust. However, fresh osage orange shavings, when mixed with a small amount of water, will discolor the water a yellowish color, while black locust shavings will cause little to no discoloration.
Notes: Heartwood fluoresces a vibrant yellow-green under a blacklight.
This genus only contains a handful of species, ranging from four to eleven recognized species depending on the author. Besides R. pseudoacacia, most species are shrubs or small trees, all of which are native to North America, and no other species are regularly utilized for commercial lumber.
|↑1||Vítková, M., Müllerová, J., Sádlo, J., Pergl, J., & Pyšek, P. (2017). Black locust (Robinia pseudoacacia) beloved and despised: a story of an invasive tree in Central Europe. Forest ecology and management, 384, 287–302.|
|↑2||Lavin, M. (1995). Phylogenetic systematics and biogeography of the tribe Robinieae (Leguminosae). Systematic Botany Monographs, 1-165.|