Trees have played an integral part in human society since time immemorial. They offer bountiful environmental services and they put so much flavor into our scenery that it’s simply impossible to imagine life without them. Trees also have symbolic value — in America, for instance, the mighty oak has become a striking symbol of the nation’s strength amidst adversity and has been declared a national tree through congressional and presidential bills.
But sometimes, trees also fall from grace — at least some of them. The black locust tree is now regarded as an invasive pest in most places, but not many know how this tree helped America survive its harsh early history.
The black locust tree (Robinia pseudoacacia, Pea Family, Fabaceae)is a common yet underappreciated tree native originally to the Appalachian Mountain range, though in time, it has become naturalized throughout the United States, southern Canada, and even in parts of Europe and Asia.
The tree can reach 40 to 100 feet in height at maturity (12 to 30 meters). Bark saplings are green and usually have a smooth texture, but when they mature, the texture turns dark brown and deeply furrowed, with flat-topped ridges. The flowers are white and fragrant and appear in drooping clusters in May and June. At first glance, it looks like an Acacia tree hence the scientific name pseudoacacia which means false acacia.
So far, nothing out of the ordinary. It’s a pretty impressive tree if you look at it closely, but you probably wouldn’t notice it in the countryside. Still, this tree carries a hidden history.
The tree that uplifted the USA
Historically, the black locust tree was regarded as the toughest tree due to its extreme resistance to rotting. Because of this extraordinary property, the tree was used to build the poles of the first buildings in Jamestown, Virginia. A hundred years after its founding, historian Mark Catesby (author of the “Natural history of Carolina, Florida and the Bahamas Islands”) visited these structures and believe it or not, these are still standing and perfectly sound. Yep, the black locust tree did an extraordinary job at supporting these buildings and it gave early colonizers the durability they so desperately needed.
Because it fixes nitrogen from the atmosphere quickly, the black locust tree grows very quickly. Farmers loved it because it was useful when establishing new farms, setting up windbreaks and shelters, as well as shade for animals while grazing. The tree was also found to support nutrition in other crops, working as a “nurse” tree for crops like barley. But most importantly, it was (and still is) the most rot-resistant wood that grows in the American climate. This makes it extremely useful for outdoor builds like fenceposts, hope poles, outdoor furniture, decks, and other projects that require weatherproof materials. It’s also very high-density and durable and has high heat tolerance.
American settlers weren’t the first to discover the properties of this tree. As recorded in the Natural History (c. 1730), this sturdy tree has also been used by American Indians to make their bows and other tools. This helped expand its range, as the American population brought the tree with them. At some point, the tree seemed to fall out of favor, until the colonists came.
The colonial times brought more fame to this tree as it played a big role in the conquest of America in the War of 1812 against the British fleet. It was believed that the British Navy’s ships were built with oak nails while American ships used locust nails. As a result, when the cannonballs from the American troops hit, the British ships easily fell apart. Meanwhile, the American ships reinforced with black locust pegs had much more durability.
After a few battles, the British realized how much of a difference the black locust tree was making — so much so that the very next year they began importing tons of locust nails to rebuild their navy ships. By 1820, the Philadelphia market was exporting 50,000 to 100,000 locust nails to England per year.
The news of this tree’s great potential spread far and wide, which made a lot of people want to grow it. The Hungary were also aware of the awesomeness of the black locust tree. They imported a lot of seeds and engaged in a wide propagation project that remains very impactful to this day. The project was so successful that nearly 20% of the forest in the country comprises black locust trees.
Losing its luster
Though valued historically, this tree today is considered by many as a weed due to its rapid opportunistic growth. It has posed a serious threat to the native vegetation in prairies, oak savannas, and forest edges, where it’s out-competing them for light and nutrients.
The black locust tree is an invasive plant in many parts of the world — and ironically, it’s invasive even on the continent to which it is native. Basically, the black locust tree can outcompete local wildlife and lead to a reduction in local biodiversity.
However, rather than seeing it as a pest, we can still regard it as a useful species. The tree is a so-called “pioneer species”, which means it’s one of the first to move into areas that have been affected by disasters (like forest fires, for instance). Black locust trees are very efficient in stabilizing erosion-prone slopes hence they can be utilized to reclaim mining sites. Additionally, the tree’s roots fix nitrogen, its flowers are a source of pollen and honey for bees, and the plant has good nutritional value for livestock feeding. Lastly, we should not forget its sturdy timber which is already tested by time as used in ship construction, railroad ties, poles, and many more.
“The black locust tree can be economically valuable and offer certain environmental benefits, but its dominant and invasive nature in Europe can have an adverse impact on biodiversity,” a European Commission report notes. “A recent study, which presents an overview of this species’ ecological and socio-economic impacts in Central Europe, recommends tolerating the tree in some areas and eradicating it in others, in order to balance its co-existence with people and nature.” The report also highlights that in some areas, the tree seems to produce no negative impact and may even help the local environment.
The black locust tree is still an area of active research. A recent study drew inspiration from its properties to develop sturdier and more resilient building materials, and especially in urban areas, they can be a useful way to cool down citizens during heat waves. No doubt, the tree still has a role to play in the future.
A tree of contradictions, the black locust tree has withstood the changing times. From being adored to now being considered a pest, it surely has come a long way. Rather than seeing the bad side, it would be better to make the most of its uses. With proper propagation protocols and careful management, the black locust tree may be able to reclaim its glory and help mankind once more.
Shiella is an MS Biology student at the UNCW. In the past four years, she's been actively involved in the conservation of threatened species that receive less attention in the Philippines. She believes it is her duty to help the public understand why science and conservation are so important.