Its native range is impossible to establish precisely because of early spread by humans, and the tree is now distributed throughout the New and Old World tropics. It grows to a height of 15-25 m (49-82 ft), with wide spreading or pendulous branches. The leaves are pale green, simple, and ovate, or trilobed or rarely five-lobed, with an acute apex, 10-20 cm (3.9-7.9 in) long. The nut is round, 4-6 cm (1.6-2.4 in) in diameter; the seed inside has a very hard seed coat and a high oil content, which allows its use as a candle (see below), hence its name.Aleurites moluccanus (or moluccana), the candlenut, is a flowering tree in the spurge family, Euphorbiaceae, also known as candleberry, Indian walnut, kemiri, varnish tree, nuez de la India, buah keras, or kukui nut tree.
The nut is often used cooked in Indonesian and Malaysian cuisine, where it is called kemiri in Indonesian or buah keras in Malay. On the island of Java in Indonesia, it is used to make a thick sauce that is eaten with vegetables and rice.
In the Philippines, the fruit and tree are traditionally known as lumbang after which Lumban, a lakeshore town in Laguna is named. Before the intrusion of non-native species, it was frequently used as a property-line manager, because the its silvery underleaf made the tree easy to distinguish from a distance.Philippine Native Trees 101: Up Close and Personal. Green Convergence for Safe Food, Healthy Environment and Sustainable Economy (Organization), Hortica Filipina Foundation, Inc, Binhi Project (Philippines). 2012. pp. 307 pages. ISBN 9789719546900.
Outside of Southeast Asia, macadamia seeds are sometimes substituted for candlenuts when they are not available, as they have a similarly high oil content and texture when pounded. The flavor, however, is quite different, as the candlenut is much more bitter. At least one cultivar in Costa Rica has no bitterness, and an improvement program could likely produce an important food crop if nontoxic varieties can be selected and propagated. A Hawaiian condiment known as ʻinamona is made from roasted kukui (candlenuts) mixed into a paste with salt. ʻInamona is a key ingredient in traditional Hawaiian poke.
In ancient Hawaiʻi, kukui nuts were burned to provide light. The nuts were strung in a row on a palm leaf midrib, lit on one end, and burned one by one every 15 minutes or so. This led to their use as a measure of time. Hawaiians also extracted the oil from the nut and burned it in a stone oil lamp called a kukui hele po (light, darkness goes) with a wick made of kapa cloth.
Hawaiians also had many other uses for the tree, including: leis from the shells, leaves, and flowers; ink for tattoos from charred nuts; a varnish with the oil; and fishermen would chew the nuts and spit them on the water to break the surface tension and remove reflections, giving them greater underwater visibility. A red-brown dye made from the inner bark was used on kapa and aho (Touchardia latifolia cordage). A coating of kukui oil helped preserve ʻupena (fishing nets). The nohona waʻa (seats), pale (gunwales) of waʻa (outrigger canoes) were made from the wood. The trunk was sometimes used to make smaller canoes used for fishing.Kukui was named the state tree of Hawaii on 1 May 1959 due to its multitude of uses. It also represents the island of Molokaʻi, whose symbolic color is the silvery green of the kukui leaf.
In Tonga, even today, ripe nuts, named tuitui, are pounded into a paste, tukilamulamu, and used as soap or shampoo. As recently as 1993, candlenuts were chewed into sweet-scented emollient used during a traditional funerary ritual in the outlying islands of the Kingdom of Tonga. Their scent was also used for making various sweet-smelling oils for the skin.
In Australia, aborigines also used them for a variety of similar purposes.
Dead wood of candlenut is eaten by a larva of a coleopteran called Agrionome fairmairei. This larva is eaten by some people.
Modern cultivation is mostly for the oil. In plantations, each tree produces 30-80 kg (66-176 lb) of nuts, and the nuts yield 15 to 20% of their weight in oil. Most of the oil is used locally rather than figuring in international trade.
In Uganda, the seed is referred to as kabakanjagala meaning "the king loves me" and is traditionally used as an improvised toy to play a marbles game fondly called dool(oo).
Because the seeds contain saponin and phorbol, they are mildly toxic when raw. However, the kukui seed oil has no known toxicity and is not an irritant, even to the eyes.
In Maui, the kukui is a symbol of enlightenment, protection, and peace. It was said that Kamapuaʻa, the hog-man fertility demigod, could transform into a kukui tree. One of the legends told of Kamapuaʻa: one day, a man beat his wife to death and buried her beneath Kamapuaʻa while he was in tree form. Because he saw that the woman had been a good person, he raised her to new life, but damned her husband to death.