The Nanu is a small tree that may grow up to 15 feet in the wild but may not grow to that height when cultivated. The leaves are 1-4 inches in length and glossy. A single white flower occurs on the end of branches. They are tubular and have 6-7 lobes. Their sweet fragrance is similar to the common gardenia. The bloom lasts for about a day. The oval fruit is green with white spots when mature and the inside of the fruit is pale yellow.

The Nanu mostly blooms in the Spring through March and may have additional flowering from December through July. The Nanu is a dry forest species that at one time was thought to have existed on all the main islands to recently becoming near extinction. Ancient Hawaiians used the wood as an anvil for pounding kapa and the fruit pulp was used to make yellow dye.