Koa (Acacia koa [Fabaceae]) is a dominant tree endemic to Hawaii, and an important component of the forest in Waikamoi Preserve. It has beautiful wood; however, "[d]espite the economic, ecological, and cultural value of koa, not a single stand of koa...in Hawaii has been through a full silvicultural rotation (i.e., establishment, stand improvement, harvest, and reestablishment)" (from USDA).
More information about koa is available from the Hawaiian Ecosystems at Risk project (HEAR).
(image by Forest & Kim Starr)
Information from TNCH's Waikamoi Preserve Plant Identification Cards:
Description: Koa, the largest native tree in Hawaii, grows up to 35 m (115 ft) tall with basal diameters up to 1.5 m (5 ft) wide. The trunk is light tan or gray; smooth on the juvenile trees, and rough and thick on mature trees. Saplings resemble koa haole, having true leaves composed of tiny leaflets. Koa seedlings (and young stems) have a fine golden fuzz on their stems, which distinguishes them from koa haole seedlings. Mature koa trees have leaves reduced to photosynthetic leaf stems, or phyllodes, which are sickle-shaped, 7.5-26 cm (3-10.4 in) long, 6-25 mm (0.25-1 in) wide, and alternately arranged. Tiny flowers form dense, greenish-yellow round heads. The fruit is a long flat pod containing ellipsoid seeds; it is ripe when it turns brown and rattles when shaken.
Distribution and Ecology: Koa occurs in dry through wet forest at 60-2,060 m (200-6,800 ft) elevation on most of the main islands. Koa forests are an important habitat for rare birds and are sensitive to grazing by ungulates.
Early Hawaiians used the hearty, rich wood for war canoes, paddles, and surfboards. Koa was not used for calabashes until modern times as the wood left an ill taste on food. The kahuna kalai wa'a, or canoe priest, took direction from the 'elepaio, an endemic bird, in selecting the right koa log. If the 'elepaio pecked at the log, it was deemed unsuitable because it was probably infested with insects, their larvae, or eggs.