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Albizia saman (Jacq.) Merr. 1876 but see additional note
pronounced: al-BITZ-ee-uh SAH-man
(Mimosaceae – the wattle family)
synonym: Samanea saman (Jacq.) Merr. 1916
pronounced: sah-MAN-ee-uh SAH-man
common names: Rain Tree, Saman Tree
Albizia was named for Filippo del Albizzi, an 18th century Florentine nobleman who introduced Albizia julibrissin (the Persian Silk Tree) into cultivation. Both Samanea and saman derive from zamang, meaning “Mimosoideae tree” in some Cariban languages of northern Venezuela.
There are many theories as to why it is called Rain Tree. These include:
• The leaflets are light-sensitive and close together on cloudy days, and also from dawn to dusk, allowing rain to fall through the canopy to the ground below.
• The grass is often much greener under a rain tree than the surrounding grass.
• Sap-sucking insects on the tree often create a steady drizzle of honeydew.
• Nectaries on the leaf petioles excrete a sugary juice that sometimes falls from the tree like rain.
• During heavy flowering, stamens can drop from the canopy like rain.
The Rain Tree has a distinctive umbrella-shaped crown, as can be seen in the tree pictured, despite the fact that it was quite severely damaged in cyclone Yasi. The crown is typically broad and domed, the horizontal spread is greater than the height when the tree is in a spacious open setting. It generally attains a maximum height of 25 m, although in rare cases it can reach 50 m. The crown typically reaches 30 m in diameter, but in very large trees 60 m is possible. Rain Trees usually have a short, stout trunk of 1–2 m DBH.
The tiny flowers (12–25 per head) are massed in pinkish heads 5–6 cm across and about 4 cm in height. The long bi-coloured stamens (white in lower half and reddish above) give the whole inflorescence the appearance of a feather duster held slightly above the foliage. Thousands of heads are borne at the same time, covering the tree in pinkish bloom. The central flower in each head is larger, stalkless, has more petals, and is incapable of forming a fruit; this flower is a nectar-producing organ that attracts pollinators. Usually only one flower per head (rarely two) is pollinated and forms a fruit. Leaves are alternately arranged along twigs and have a prominent swelling at the petiole base; stipules are present and threadlike; the leaf blades are bipinnately compound, arranged in 2–6 pairs of paripinnate pinnae, each bearing 6–16 rhombic leaflets, shiny green above, dull and finely hairy beneath, 2–4 by 1–2 cm in size, the apical leaflets largest. During dry periods, the trees are semi-deciduous, losing their leaves for a short period. Where there is a definite dry season, they may remain leafless for a period of weeks, but refoliate quickly when there is adequate moisture. Mature pods are black-brown, oblong, lumpy, 10–23 cm long, 1.5–2 cm wide, thick, straight or slightly curved, not dehiscing but eventually cracking irregularly, and filled with a sticky brownish pulp that is sweet and edible.
Extensive cultivation has obscured the native range of the species; but it is believed to be native in northern South America and in Central America as far north as El Salvador. It is now widespread from Mexico south to Peru, Bolivia and Brazil. In these areas, it occurs in low-elevation dry forests and savannah habitats. It is now cultivated and naturalized throughout the tropics. There are some magnificent specimens of the tree in Townsville: some that come immediately to mind are in the grounds of the Mundingburra State School and of the Cathedral School in Aitkenvale.
The wood could be developed more widely as a commercial timber, comparing favorably to black walnut. The wood must be rough cut and carved within several weeks, as otherwise it dries out, becomes stringy, and breaks up easily if carved too dry. The sapwood is narrow and white to light cinnamon. The heartwood is straight or cross grained with a medium to coarse texture and ranges from browns to almost black. The wood requires careful drying because of shrinkage and moderate to severe warp.
Photographs taken 2010, 2014 Picnic Bay & 2012, Nelly Bay
Page last updated 10th Jult 2018