Koai‘a is another native species that comes from the Fabaceae (Pea) family of plants. Many people are familiar with Acacia koa, the typical forest koa that is revered around the world as one of the most beautiful hardwoods in existence. Koai‘a is in the same genus, but grows in much drier conditions throughout the Hawaiian Islands. Existing from 150’ to roughly 4000’ elevation on leeward coasts, Koai‘a is a small tree that grows to heights of 15’ to 30’ and a spread of up to 20’. The true leaves of both Koa and Koai’a are found on younger plants and new shoots of adults and are fleshy green compound leaves. The adult photosynthetic structures, called phyllodes, are actually modified stems that become flat and hook shaped as the tree matures. Next time you are around Koai‘a, take some time to look for both structures! Flowers appear as a pale yellow to white “puffs” which ultimately result in seed pods with vertically arranged seeds.
In the landscape setting, koai‘a makes for a great shade tree or privacy screening plant. Growing much smaller in stature than koa, it makes for a great specimen plant in the yard. This xeriscape compatible plant requires very little water and is resistant to most pests and is more resilient to diseases than koa. The trees handle well in full to partial sun, and can be planted in a variety of soil types from clay to cinder, as long as the soil is well draining. Plant a koai‘a in your yard to help promote this wonderful endemic species!
Historically, koai‘a has been used for a variety of different things from making spears, to housing construction, to the making of musical instruments. Koai‘a is slower growing than its cousin koa, and produces a wood that is much harder. Koai‘a is more adept to producing a curly grain throughout the wood and thus, not favored in making wa‘a (canoe). The leaves of the plant were made into beautiful lei, and could also be crushed and mixed with other plants to treat various skin disorders.
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