Reutealis trisperma aka Banucalag Nut

Reutealis trisperma is an evergreen tree from the Philippines. It belongs to the spurge family, Euphorbiaceae. Its common names include Otaheite walnut and lumbang tree. It grows wild in forests at low and middle elevations. Its native climate is wet and tropical. People also grow it in Southeast Asia for seed oil and medicinal use.

The tree forms a dense crown and grows fast. Garden references give a height and spread of about 39 feet [12 metres]. Other accounts place its maximum height at 49 feet [15 metres]. The trunk can reach about 1.1 feet [0.35 metres] across. Young trees may reach 16 feet [5 metres] within five years. They can start bearing fruit within a few years from seed. The crown keeps its leaves year-round.

This tree suits tropical and subtropical growing conditions. It needs a sunny site and does not grow in shade. It prefers moist soil that drains well. It can grow in sand, loam, or clay. Its soil range includes mildly acid, neutral, and mildly alkaline ground. Sources report brief frost tolerance down to about −2°C. This does not imply tolerance of long periods of freezing weather. Plants For A Future lists USDA zones 9–12. Fresh seed can germinate within 19 days under reported conditions.

The seeds yield an oil that dries fast. Reported seed oil content reaches 56 percent. People use it in paints, varnishes, soaps, and boat coatings. It also serves as fuel and an insecticide. In the Philippines, people once made soap from this oil for sailors. That soap could form lather in seawater. The seed cake left after oil extraction serves as fertilizer. These uses explain why people cultivate the tree beyond its forest habitat.

The fruit is poisonous, and no food use is supported. Even part of a kernel can cause severe illness. Reported effects include burning in the mouth, throat, and stomach. Vomiting may begin within half an hour. Diarrhoea may start later and last 12–24 hours. Records describe medicinal use of the plant for skin problems. They also describe bark sap use for scalp scaling. The sources suggest oil use for wounds and burns, but leave its exact role uncertain. These records do not establish safe home treatments.