Anyone living in Singapore who visited our local parks and gardens or drives along the expressways would have noticed the gregarious flowering of two species of trees lately. The trees in flower belong to the genus Alstonia and there are two species widely planted in Singapore. I managed to capture some pictures of one of the flowering A. scholaris that was flowering in HortPark before I left home from work.
They include A. scholaris and A. angustiloba. Both species are native to this part of the world and are members of the frangipani family, Apocynaceae (and expectedly, they exude a white milky sap when any part of the plant is injured). The fruits of Alstonia occur as a pair of long, narrow cylindrical pods that are joined at the base. Seeds are small and flat. Alstonia scholaris is commonly known as the Common Pulai while A. angustiloba is known as Indian Pulai.
In the latest edition of Trees of our Garden City edited by Mr Tee Swee Ping, Alstonias are described to be tall trees that can grow up to 25 m tall and feature a large, pagoda-shaped crown with distinct tiered branching. The leaves of Alstonia are borne in whorls of up to 8 leaves. Each leaflet is oval-shaped. The two common species can be distinguished via their leaf and fruit sizes. The leaves and fruits of A. angustiloba are slightly larger.
The colour of their flowers varies also. The flowers of Alstonia are produced in clusters of 3 to 8 and each flower is rather small. Alstonia angustiloba’s flowers are white in colour whereas those of A. scholaris are greenish yellow . They are both heavily scented and flowering is triggered by a marked dry season. 2009′s December, I find, is unusually dry in Singapore.
Besides being valued as handsome trees that profusely produce scented flowers, Alstonia has various other uses. The sap, which contain alkaloids, exuded from the bark of Alstonia has medicinal properties. The rather light timber from Alstonia is used to make a range of products, from posts, coffins, corks, household utensils, floats to boards. In particular, timber from A. scholaris is used in the past to make writing slates for schools, which gave rise to the species name scholaris.
