Alstonia iwahigensis Elmer, Leafl. Philipp. Bot. 4 (1912)

Latin for 'From the river Iwahig', a river on the island Palawan in the Philippines

Often considered a synonym of Alstonia angustiloba.

Tree with abundant white sap. Leaves in whorls, lower surface whitish, secondary veins placed close together at perpendicular angle to the midvein. Very similar to Alstonia scholaris, but missing the ligule at the base of the petioles. Flowers with corolla tubes more than twice as long as corolla lobes (as oppose to shorter for Alstonia angustiloba). Fruits very long and narrow, greenish, glabrous (as opposed to hairy in Alstonia angustiloba), placed in pairs; splitting open to expose many small seeds with two tufts of hairs for wind dispersal.

A medium-sized to large tree up to 45(-70) m tall, bole tall, straight, fluted, up to 109 cm in diameter, buttresses straight, up to 6 m tall and spreading out at the base for about 2 m, outer bark greyish, yellowish or dark brown, smooth to slightly rough inner bark yellow or pale yellow, with copious latex; leaves in whorls of 4-7, elliptical to obovate, 3.5-10 cm x 1.5-4 cm, apex obtuse or rounded, with 25-40 pairs of secondary veins, petiole (5-)10-20(-28) mm long; inflorescence usually forming 2 bunches of dense and many-flowered clusters, pedicel 1-2 mm long, calyx variably pubescent, corolla glabrous outside except for the lobe margins; follicles glabrous, up to 340 mm long, filled with many small hairy seeds which are wind dispersed. [from PROSEA]

Occurs on hillsides, both on sandy and loamy soils in primary and secondary forest at 20-800 m altitude. Usually in mixed dipterocarp forest, but also found on the edge of peat swamp and in swamp forest. Usually on sandy soils, but also on clay, loam and ultrabsaic soils. Growing on alluvial sites, but more often on hillsides and ridges.

In Sabah, the diluted latex is drunk to cure fevers. A decoction of the roots is taken to treat diabetes and lumbago. The latex mixed with honey is taken as a tonic.

Borneo and the Philippines.

Local names
Borneo: Pelantan; Pulai; Pulai basung; Pulai gunung; Pulantan; Selutong; Tambirag; Tomboilik.
Indonesia: pulai gunung, pelantan (East Kalimantan).
Malaysia: tombalik (Bundu Tuhan, Sarawak), tambalait (Murut, Sabah).