Albizia lebbeck - Lebbeck tree

Albizia lebbeck, also known as the Black Siris, is a tropical tree belonging to the Fabaceae family, closely related to Albizia julibrissin. Native to warm regions of Asia and Africa, it is well-suited to tropical and subtropical climates with a dry season but struggles in cold conditions. This fast-growing, elegant, and exotic tree captivates with its habit, finely divided foliage, and beautiful fragrant cream-yellow flowers. In Mediterranean climates, it can be used as a shade tree in gardens or to enhance green spaces.

Albizia lebbeck originates from tropical Asia, with its natural range extending from the Indian subcontinent to Southeast Asia. It is also found in Africa, where it was introduced, as well as in Central America and the Caribbean. In its natural habitat, it often grows in plains and savannah areas, thriving in well-drained or even dry soil. This species plays an important ecological role as a nitrogen fixer in its native lands. Albizia lebbeck is a fast-growing deciduous tree, typically reaching between 15 and 20 metres in height, and up to 30 metres under optimal conditions. Its habit is broad and spreading, with a rounded crown that can extend up to 15 or 20 metres in diameter. Its grey to brown bark is often fissured on older specimens, while young stems have a smooth texture. The foliage consists of bipinnate compound leaves with 2 to 4 pairs of pinnae, each divided into 6 to 18 oblong leaflets measuring 1.5 to 6.5 cm in length. Their colour ranges from light to dark green. The leaflets fold up in the evening. In autumn or during the dry season, depending on the climate, the leaves fall, leaving the tree bare until new growth resumes.
Flowering occurs in spring and summer, between May and August in Europe, earlier in Mediterranean regions. It takes the form of globular inflorescences, spherical clusters measuring 5 to 9 cm in diameter, located at the ends of axes or in the axils of leaves. Each cluster consists of 15 to 40 small hermaphroditic flowers. The highly fragrant flowers are white to cream-yellow, sometimes with pale yellow or greenish tones. They feature numerous prominent stamens, measuring between 2.5 and 3.8 cm in length, giving them a fluffy or pom-pom-like appearance. These stamens are usually white or cream, may have pale green tips and tend to yellow over time. The flowers are nectar-rich, attracting numerous pollinators. The fruits are flat, elongated, 15 to 30 cm long pods, which remain on the tree even after the leaves have fallen. The seeds they contain are used in some countries for their medicinal properties. Its durable, lightweight wood is widely used for furniture-making, carpentry, and even paper pulp.

The Black Siris is valued for its versatility in favourable climates. In dry gardens, it is ideal for creating shade. It can also serve as a windbreak in exposed areas. Ecologically, it enriches the soil by fixing nitrogen, promoting the growth of surrounding plants. This tree fits perfectly into exotic or Mediterranean settings. It can be used in a woodland composition to create a canopy effect. Plant it alongside Jacaranda mimosifolia, Delonix regia, Bauhinia acuminata, and Caesalpinia pulcherrima, for example—plants that perfectly complement this tropical palette.

The common name "Black Siris" given to Albizia lebbeck stems from its introduction to Réunion in 1767 to shade coffee plantations. In this region, the tree is called "bois noir des bas" (Black Siris) to distinguish it from the "bois noir des hauts" (Diospyros borbonica), an endemic species of the island found in humid forests at low to mid-altitudes. In reality, the wood of this tree is light to brownish, with a fine texture and moderate density.