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: 65-100 ft (20-30 m) tall, 2-3 ft (.6-1 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; narrow to medium rays barely visible without lens, spacing normal; parenchyma vasicentric, lozenge, 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)

  • David Shipway

    This species grows well when planted on farmland on the southern BC coast, and is a local favourite for crooks, knees and ribs in traditional boatbuilding. It is dimensionally stable and extremely rot resistant, similar but harder/tougher than teak. I find that working and sanding the raw wood does not irritate eyes or skin as much as teak does, but it does irritate the nasal passages, and also causes something almost like a mild case of asthma – constriction in the bronchial tubes. I highly recommend wearing a particle filter mask when working with Black Locust.

  • david cullen

    I had four acacia trees in my yard cut down and sawn on the property.
    The wood is extremely hard and makes exceptionally fine wood for furniture. The wood takes stain well and once the moisture level gets down to 6% it machinabilty is excellent.The biggest problem is drying the wood to prevent warpage. I am now in the process of having two trunks that were cut down three years ago sawn into boards. When this is done I will know how the warpage works out.
    Once the warped boards are cut they remain stable and I have made several pieces of furniture that very good. This area of the province has many acacia tree which grow to about 15 to20 M in height. This summer I am cutting down two more trees to put into my reserve foe the future.

  • michael

    This wood is very hard and i think quite a beautiful wood. Contrary to the description above, it has a very peculiar smell that is at first agreeable but soon becomes a bit too pungent /disagreeable. Over the course of a day of milling i realized the i was developing a sensitivity ( allergy) to the wood. I got a low grade nausea and a head ache. The next day i tried milling the wood without a respirator and soon found the headache coming on. Years ago making a deck out of western cedar I had a similar reaction. It took about a week for the sensitization to happen but became quite severe. I work with a lot of wood and these are the only two that require i use a full respirator to work with. It’s very strange to have an allergy to certain woods and not to others. Throw this out there for any others who may have a similar disposition.

    • Randy Gage

      Iworked three days with western Cedar and a week later was hospitallized with pnumonnia. Go figure.

  • Robin

    When finding a black locust tree, it is recognizable from its coarse bark, it’s leaf pattern and its white flowers although there semm to be some new yellow flower cultivars such as Robinia pseudoacacia spp “Frisia” , resembling closely Laburnum anagyroides trees who are also Fabaceae and bear similar flowers and grow in the same regions, same climate.

    Laburnum trees have (unlike Robinia)a smooth and thin bark, and the leaves are alternated differently, but the wood is pretty similar, once expose to light, the creamy yellow Black Locust will resemble the initially honey light golden brown Laburnum , only one who knows well both woods will notice the slightly coarser grain of the black locust.

    But comparing sun exposed endgrain cut “oyster” slabs of both woods, they’re very very similar : just look at the endgrain photos of black locust (robinia pseudoacacia) and laburnum anagyroides on wood-database.com and you’ll see for yourselves! The similarities of endgrain characteristics are stunning.

    Conclusion: there can be confusion between both if not careful.

  • Anna Sternfeldt

    Nice to find this site. I am amazed by Black Locust having so many advantages. Being a hard wood being able to thrive in temperate climate will make it a candidate for replacing the need for rainforest trees which is great. And also having the asset of being a legume which reduces the need for fertilizer, and this is just a few things… I have put some info together myself on Black Locust that may complement the interesting info on this site: http://hub.me/aeHwO

    • Alan Drake

      Your locust link is dead.

  • Mike Sillett

    I am planning on making a 10 – 12 ft. long chisel ( actually i will be attaching a chisel to one end ).

    The purpose is to chisel off growths high up on a tree trunk. I will be hammering from the lower end – maybe with a wood maul – or using it above my head to continuously jab away .

    I am considering white oak, black locust and dogwood however maybe there is another type of domestic wood more suitable?

    Does anyone with more wood knowledge than me have any ideas, recommendations or suggestions?

  • Benton Frisse

    Anyone have any ideas on how this would do as a striking tool handle? Primarily an ax or hammer handle?

  • JPVan

    Grows like a weed — at a height of 25′ you have three 8′ sections to be quartered and the result is 12 fenceposts. Working with one other guy, and setting aside land and materials cost, we had a system where we were producing $192/hr in cash and carry inventory and could scarcely keep up with demand when we were 25% cheaper than an inferior product at nearby farm supply stores.

  • jet

    Black locust is a toxic plant due to the toxalbumin content, most animals can’t eat it without getting sick. I suspect that’s why it lasts so long outdoors without surface treatment, the toxins in the sap kill off mold, mildew, and many bugs. I see paper wasps on the lumber and where they’ve taken their bit of the nest off a cured board.

    I built a deck out of it a few years ago and it’s now a really nice shade of grey after a summer with plenty of sunlight. Every splinter I got while building that deck made my skin swell up like I’d been stung by a wasp and I made a point of not breathing any of the sawdust from the cuts. I also had to drill holes for the umpteen thousand screws, putting a screw in black locust is like putting a screw in metal. It’s durable stuff and if you’re in Pennsylvania it’s almost free.

  • David Breeze

    One note of caution: With all its positive attributes you may be tempted to plant Black Locust on your property. Be aware that it is somewhere near the top of the scale for invasiveness! I sprouted 5 seeds a few years back and planted them in a corner of my lot. Three years later there were locust sprouts coming up in a garden 70 feet away from the little trees – and the trees had not borne seeds yet. But they had sent out finger-sized roots 100 feet long, seeking fertile ground and ready to create new trees from any fragment of root left in the ground. Don’t start a fight you can’t win!

  • Vasco Chit

    Hello every body,
    Can anyone recommend me some suppliers of Robinia wood in Europe? I am looking quite big quantities of this wood.

    • Alan Drake

      I am going to source mine from Arkansas for flooring in a new home in New Orleans. I could have put in a container to EU. My email is AlanSDrake at a gmail account.