Nature Diary
Rain tree: Albizia saman

Called Siris or Shirish in many parts of northern India and Bengal, chakkarakkay maram in Malayalam, and the mazhai maram or thoongu moonji maram in Tamil, this tree is very common in the tropics. Saman is its native name in Brazil but it grows in Mexico, Peru, South and South East Asia including India as well as the Pacific Islands such as Hawaii. It is cultivated throughout the tropics as a shade tree, although it has shallow roots and easily falls down in the rain or storm.
Saman is a wide-canopied tree with a large symmetrical crown. It usually reaches a height of 25 m and a diameter of 40 cm. It has evergreen soft foliage which is dotted all over with pink and white flowers from March to May (see cover photo). In June the pods come out although a few flowers can be seen all the year around. The flowers are like silken bunches with one central and a surrounding crown of florets, upto 20 in number. The stamens are half pink and half white and prominently stick out of the flowers. Sometimes the flowers are cream-gold.
The leaves are long and feathery while the bark is dark grey and tough. Each pinna contains four to eight pairs which bear three to seven pairs of leaflets. They are oval-shaped without a stalk and become bigger towards the tip. During the day, they spread out horizontally, not allowing sunlight to pass, which is why they make good shade trees. However, at night or during the rainy season, the pairs of the leaflets fold together, the leaf stalks bow down and each pinna rotates so that the leaves all lie sideways. This sleeping habit has given it the name thoongu moonji maram (sleepy-face tree) in Tamil.
In India people strongly believe that the name `Rain Tree` was given because the trees posses an interesting habit of occasionally spraying the ground beneath with moisture. However, later botanists discovered that the spraying was caused because of the innumerable minute insects called cicadas feeding on the leaves that discharge this shower.
The fruit of the rain tree is a fleshy pod. The seeds are contained in the brown sugary pulp of the pod. People use the leaves as fodder. The timber of the tree is soft and light and that is another reason why it easily falls over in stormy weather. However, after being watered for only 3-4 years, the tree grows to a height of 3 m or more, and then spreads out over great areas and great heights; hence they are still popular as avenue trees although neem and tamarind trees have more dense wood and are much more sturdy.
The photo shows the leaves of the tree and a flower being pollinated by a bee (image courtesy Wikimedia Commons).