Endemic
Nānū or Na`u, is one of three Gardenia species endemic to Hawai`i: G. brighamii H. Mann, G. mannii H. St. John & Kuykendall, and G. remyi H. Mann. Gardenia brighamii is an endangered species that once existed on all the main islands. It grows in dry forests.
Nānū can grow up to 20' high in the wild. It has a woody, brown trunk. In the wild, leaves can be found only on the ends of the branches. In the cultivated version, the foliage is much fuller. Nānū is named for its glossy, dark green broad leaves which can grow to 4 inches in length. Single, white flowers grow at the end of the branches. They are tubular in shape with 6 to seven lobes. The fragrant flowers open in late afternoon. Round, or oval green fruits are 1" - 1 1/2" in size and contain the plant seeds within. The flowering and fruiting season of the Nānū on Oah`u is between the fall and winter.
A Tropical Garden Flora by George W. Staples and Derral R. Herbst
https://www.ctahr.hawaii.edu/hawnprop/plants/gar-brig.htm