It is a large tree which grows to a height of 50 feet when cultivated, much much older trees, however, can grow much taller. At full maturity, theses tree= s are 10 to 25 feet in diameter. A Koa tree can grow as much as an inch in diameter per year. The leaves of Hawaii’s Acacia Koa are not true leaves; they are modified leaf stems, or phyllodes, which function as leaves. These crescent-shaped phyllodes are gray-green and range from 3 to 9 1/2 inches in length. Small, yellow, powder-puff shaped flowers occur in clusters either at the ends of its branches or at the bases of the phyllodes. There are three forms of Acacia koa which are sometimes considered subspecies. One of these, subspecies koaia, is shorter with a more gnarled appearance and is commonly considered horticulturally distinct. (Bornhorst 1996; Wagner 1990)

Hawaii’s koa is one of the world’s premier furniture and crafting woods because of its rarity and depth of figure (grain, color and patterns). It is a medium density hardwood similar to walnut but its color can vary from a pale blond to a deep chocolate brown-black. The grain in the wood can change directions from one layer to the next so that solid koa often takes on a three-dimensional quality when rubbed with oil. Koa can be a difficult wood to work with as it burns easily and has a tendency to tear-out even with the best of carbide blades. This adds to the expense of items made from koa as more wood has to be sanded away to achieve certain shapes. Larger pieces of furniture may require long preparation times as raw timber must be carefully selected from whatever stock becomes available so that all the necessary pieces are similar in grain, color and figure. All of this makes koa a very labor intensive medium.