The scientific name of the acacia tree is Robinia pseudoacacia. It’s also commonly known as black locust or simply robinia and is widely found in our country. Originally from North America, where it forms pure forests, it was imported to the old continent at the beginning of the seventeenth century by J. Robin, who took care of the botanical garden of the King of France. It arrived in Italy two centuries later and quickly began to spread and gain importance in forestry. It’s a highly invasive species, capable of adapting to any type of soil, from flatlands to hills.
In this article, we’ll explore the characteristics of the acacia, understand its environmental functions in the ecosystem, and also grasp the risks of its excessive expansion.
Characteristics of the Acacia
The name acacia derives from the Greek term akis = spine. This refers to one of the main features of this species, which is its branches covered with strong thorns. The tree belongs to the botanical family of Fabaceae and is deciduous, meaning it sheds its leaves during winter. It can have an upright posture in optimal growth conditions but can also take the form of a bushy shrub in more challenging soils. It has a taproot initially, then becomes superficial and widespread, with a strong tendency to sucker. Being a legume, it forms a symbiosis with bacteria of the genus Rhizobium, which fix atmospheric nitrogen in the soil.
In its tree form, it can reach heights of 25-30 meters, developing a robust trunk with unmistakable characteristics. As a young tree, the black locust has a bark with reticulated designs, then becomes cracked with longitudinal incisions and prominent knots. The color initially is reddish-brown, maturing to a grayish hue.
The leaves of the acacia are alternate on the thorny branches, with a petiole, and are pinnately compound. They are oval-elliptical in shape, with a bright green color on the upper side and a paler shade on the underside.
The flowers of the acacia are the most precious part of the tree. They are hermaphroditic and are grouped in raceme inflorescences, ranging from 10 to 30 cm in length. They are located at the axils of the leaves. They have the typical corolla of the Fabaceae family, similar to that of the bean, and are white in color. They are very conspicuous, fragrant, and rich in nectar. These flowers are particularly loved by bees, which produce a clear, fluid, and very tasty monofloral honey: the famous acacia honey. Thus, it’s a melliferous species that blooms from April to June.
The fruits of the acacia are legumes, ranging from 5 to 10 cm in size. They have a flattened shape, reddish-brown in color, filled with kidney-shaped, very hard, brown seeds with dark spots. The pod opens upon maturity in the fall but persists on the tree even in winter.
Culinary Uses of Acacia
Besides producing the delicious acacia honey, the flowers are also edible on their own.They can be harvested before they fully open and should be stripped of their stems. They are used to prepare excellent mixed jams, to which they give a pleasant aroma. Somewhat similar to the elderflower, the acacia flower is sweet and fragrant. In some regions, the entire cluster is dipped in batter and then fried, resulting in a tasty dish that will amaze your guests. From the flowers, a precious essential oil is also extracted, which is used in perfumery. The seeds are also edible, but they lack significant taste and value. Other parts of the plant are toxic, especially the thorns, whose sting causes significant inflammation. A great acacia honey can be found here.
Besides its use in beekeeping, acacia can also have significant applications in forestry. It is highly valued for its ability to stabilize sloping and vulnerable soils. Moreover, it’s a species highly resistant to fires and can be a pioneer species.
Issues Related to Acacia
However, in Europe, the black locust is considered invasive due to its rapid growth and spread. With its extensive root system, it risks suffocating young plants of native species, such as oak and chestnut. Furthermore, its high adaptability makes it thrive from the coast to altitudes of over 1000 meters. The consequence is a homogenization of the vegetation layers, leading to a loss in biodiversity.