Acacia koa for up to 25 years. Scarification is needed before "A. koa" seeds will germinate. Koa is endemic to the islands of Hawaii, Molokai, Maui, Lānai, Oahu, and Kauai, where it grows at elevations of . It requires of annual rainfall. Acidic to neutral soils (pH of 4-7.4) that are either an Inceptisol derived from volcanic ash or a well-drained histosol are preferred. Its ability to fix nitrogen allows it to grow in very young volcanic soils. Koa and ōhia lehua ("Metrosideros polymorpha") dominate the canopy of mixed mesic forests. It is also common in wet forests. The koa's trunk was
Acacia koaia It can be seen on ranch land in North Kohala, and at a small fenced exclosure outside of Waimea known as the "koaia" sanctuary. "Koaia" is one of the species being used to revegetate the island of Kahoolawe, which lost most of its plant life to overgrazing and ordnance testing. Native Hawaiians ground "koaia" leaves and bark with "auaukoi" ("Senna occidentalis") and "kikānia pipili" ("Desmodium sandwicense") stalks. The mixture was then hydrated and used in a steam bath to treat diseased skin. The wood of "koaia" is harder and more dense than that of "koa". It was used to make