Black Locust
August 14, 2011 | 5:33 pm CDT

There is a legend about the tenacity of the black locust mentioned in the book Cold Mountain by Charles Frazier. Supposedly the tree has such a "will to live" that when it is cut into fence posts and anchored back in the ground as fencing, the posts grow roots and sprout limbs again.

While that may be folklore, black locust is remarkable for its qualities of strength and durability. Fence posts have long been made from the very hard, strong and heavy wood of black locusts. Poles, ties, mine timbers and stakes are also made from black locust. Other uses include wheels, barrows, wagon bottoms, boat planking, vehicle bodies, weather boards, boxes, crates, woodenware and gates. Black locust was also a popular choice for "tree nails" used in ship construction. Its other important use is as a "protector" or conservation tree. Black locusts provide a shield from the wind and can help prevent soil erosion.

A 'Wannabe' Furniture Wood
Black locust's utilitarian uses exceed its use for furniture and cabinetry. But the wood does have an attractive straight grain that is sometimes described as "prominent." Black locust is sometimes used for joinery and cabinetwork and sliced for decorative veneers, but as a furniture wood, it is described as a "wannabe" by some American veneer companies.

Black locust, which has a greenish-yellow tint when first cut which deepens to a golden color, is known more as a fence post wood than a wood for furniture. Some veneer companies are of the opinion that, while locust does have an interesting grain, the wood excels in outdoor uses when strength and durability are an issue, especially when wood is anchored in the soil.

The wood can pose problems when working with tools due to the coarse texture of the wood. Cutting tools should be kept sharp to avoid blunting. Pre-boring is recommended when nailing. Black locust glues easily and stains well.

A Successful Transplant
Black locust is considered to be the most valuable of the five locusts which grow naturally in North America. Its botanical name offers a key to the tree's identity. Robinia pseudoacacia is named in honor of a famous scientist-herbalist named Jean Robin. The name pseudoacacia refers to the fact that black locust, while similar in many ways to an acacia tree, is not a true acacia. Still, the common names of the tree in North America include acacia and false acacia.

Robinia pseudoacacia of the Family Leguminosae

Black locust, false acacia, robinia, honey locust, pea flower, post locust, yellow locust, green locust and white locust.

Tree attains heights of 70 to 80 feet with diameters of 3 to 4 feet. Weight ranges from 34 to 54 pounds per cubic foot with an average weight of 45 pounds per cubic foot. Specific gravity 0.72.

Wood is very heavy, very hard, exceedingly strong and stiff, and has very high shock resistance and high nail-holding qualities. Heartwood has high decay resistance. Wood is very durable and tough. Medium strength in bending. Timber dries slowly with tendency to distort or warp. Medium movement in service. Wood has good steam bending qualities, equal to ash and beech. Steamed wood will stain when in contact with metals.

In Great Britain, black locust is sometimes called robinia. In the 16th and 17th centuries, Robin, curator of the Paris Jardin des Plantes, transplanted black locusts from America to Europe. In the book Hugh Johnson's Encyclopedia of Trees, Johnson writes that, "The black locust was one of the first American trees to be sent back to Europe. By about 1600 Jean Robin, Henry IV's herbalist, was growing it in Paris. It derives its generic name of Robinia from him and its specific name of pseudoacacia from its obvious similarity to the subtropical acacias of Africa. There are no European acacias. The acacia can hardly have been a well-known plant in the 17th Century. Yet for some reason its name stuck and to this day in England, acacia means robinia."

Other trees of the New World that were early transplants from Europe include the tulip tree, swamp cypress, eastern red cedar, magnolia, flowering dogwood, white pine and scarlet oak.

Black locust grows from Pennsylvania along the Appalachian Mountains to Northern Georgia and is also native to a small part of Arkansas and grows in the eastern and southeastern part of Canada. The name locust refers to some 20 various plants native to North America. Black locust is widely planted in the United States and Canada as an ornamental tree and is prized for its shade as well as its fragrant flowers.

Black locust is one of the most widely transplanted of all native American trees in Europe. The tree has also been successfully transplanted to Asia, North Africa and New Zealand.

Black locust trees have a "fruit," a long, glossy brown pod with roughly a dozen wax seeds. The trees are fast growing when located in rich soil. The older trees are endangered by the locust borer insect but they are remarkably resistant to attack by termites.

Other lesser-known locusts include the rose acacia (Robinia hispidas) from the southeast United States and the clammy locust (Robinia viscosa) from North Carolina. Some people confuse black locusts and honey locusts, however honey locust is a member of the genus Gleditsia triancanthos. Locust trees are divided into three different genera: Robinia, Gleditsia, and Ceratonia.

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