Botany, Ecology and Diversity of Acacia Koa in the Hawaiian Islands

Acacia koa (koa) is a valuable leguminous timber-wood tree endemic to the Hawaiian Islands. Over the past century, conversion of some native forests for agriculture and ranching, uncontrolled spread of invasive plant species and outbreak of a deadly fungal wilt disease severely reduced A. koa forests. However, recently there has been a growing interest in re-establishing A. koa as an agroforestry tree because the tree has significant importance in economy, ecology and culture of Hawai‘i. This review presents the current knowledge on A. koa, including its ecological roles, various morphological forms, genetics, evolution and development of methods for seedling selection and propagation. A better understanding and awareness of the nature of A. koa will help successful development of wilt-resistant A. koa trees with high wood quality that can support Hawaii’s ecology, economy and culture.