The Honuaula forest reserve on the southwestern flank of the volcano at , preserves an extensive koa ("Acacia koa") forest stand, with smaller Naio ("Myoporum sandwicense") and Māmane ("Sophora chrysophylla") trees and an undergrowth of Ākala ("Rubus hawaiensis") and various ferns. The reserve measures and protects an ecosystem that has since been largely deforested in the surrounding area. The Wai Aha spring reserve on the lower slopes of the mountain is somewhat swampy and is home to the flowering evergreen ōhia ("Metrosideros polymorpha"), the woody climber Ieie ("Freycinetia arborea"), and a dense undergrowth of Amau ("Sadleria cyatheoides").