Albizia is a genus of about 150 species of mostly fast-growing subtropical and tropical trees and shrubs in the subfamily Mimosoideae of the legume family, Fabaceae. The genus is pantropical, occurring in Asia, Africa, Madagascar, Central, South, and southern North America and Australia, but mostly in the Old World tropics. Some species are considered weedy.
They are commonly called silk plant or sirises. Peculiarly, the obsolete form of spelling the generic name - with double 'z' - has stuck, so that another commonly used term is albizzias (though the form albizias is also found, particularly in species that are not widely known under a common name). The generic name refers to the Italian nobleman Filippo degli Albizzi, who in the mid-18th century introduced siris to Europe.
These are usually small trees or shrubs with a short lifespan - though the famous Samán del Guère near Maracay in Venezuela is a huge Albizia saman specimen and several hundred years old. The leaves are pinnately or bipinnately compound. Their small flowers are in bundles, with showy stamens much longer than the petals. Confusingly, some species are given the name "mimosa" which correctly belongs to species in the related genus Mimosa. Unlike those of Mimosa, Albizia flowers have much more than 10 stamens. Albizia can also be told apart from another large related genus, Acacia, since its flowers have their stamens joined at the base whereas in Acacia stamens are free (separated).
Albizia saman (sometimes treated under the obsolete name Samanea saman) is a species of flowering tree in the pea family, Fabaceae, that is native to the Neotropics. Its range extends from Mexico south to Peru and Brazil, but it has been widely introduced to South and Southeast Asia, as well as the Pacific Islands, including Hawaii. Common names include saman, rain tree and monkeypod (see also below). It is often placed in the genus Samanea, which by yet other authors is subsumed in Albizia entirely.