Kauila, Colubrina oppositifolia Brongn, ex H. Mann, is a medium-tree, with thin oblong leaves which are bright green on both sides. This is a rare native tree found only in Hawaii and Oahu. It's a member of the family Rhamnaceae (Buckthorn family). The bark of the tree is light brown, with a very hard, reddish wood that sinks in water. The wood was formerly valued by the early Hawaiians for spears and tapa beaters. Part of the plant was also used medicinally.
The Hawaiian kauila (Alphitonia ponderosa Hillebr.) also produces dense wood that sinks in water. Its leaves are alternate, thin, oblong, grayish to rusty wooly on the undersurface. This species is found in the six largest Hawaiian islands. This is one of the hardest, densest native wood that replaced metals in the economy of the ancient Hawaiians.
Kauila is a rare native Hawaiian tree found in dry to mesic forests on all the main islands, except Niihau and Kahoolawe. There are two endemic species of kauila in Hawaii: Alphitonia ponderosa Hillebr. and Colubrina oppositifolia Brongn, ex H. Mann, both belong to family Rhamnaceae. Both species produce the hardiest and heaviest native woods that were useful to the Hawaiians.