Albizia lebbeck is a species of Albizia, native to Indomalaya, New Guinea and Northern Australia and widely cultivated and naturalised in other tropical and subtropical regions. English names for it include lebbeck, lebbek tree, flea tree, frywood, koko and woman’s tongue tree. The latter name is a play on the sound the seeds make as they rattle inside the pods. Being one of the most widespread and common species of Albizia worldwide, it is often simply called siris, though this name may refer to any locally common member of the genus.
It is a tree growing to a height of 18–30 m tall with a trunk 50 cm to 1 m in diameter. The leaves are bipinnate, 7.5–15 cm long, with one to four pairs of pinnae, each pinna with 6–18 leaflets. The flowers are white, with numerous 2.5–3.8 cm long stamens, and very fragrant. The fruit is a pod 15–30 cm long and 2.5-5.0 cm broad, containing six to twelve seeds.
In the West Indies and certain parts of South America this tree is known as a ‘Shak Shak Tree’ because of the sound the seeds make in the pod.