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
Mauna Kea State Recreation Area. A band of ranch land on Mauna Kea's lower slopes was formerly "Acacia koa" – "Metrosideros polymorpha" (koa-ōhia) forest. Its destruction was driven by an influx of European and American settlers in the early 19th century, as extensive logging during the 1830s provided lumber for new homes. Vast swathes of the forest were burned and cleared for sugarcane plantations. Most of the houses on the island were built of koa, and those parts of the forest that survived became a source for firewood to power boilers on the sugarcane plantations and to heat homes. The once vast