Acacia koa -- Koa



Photos by Priscilla Millen.
Koa, or Acacia koa,
is found on all the main islands in dry, mesic, and wet forests. It is one of the major forest trees of Hawai'i.
It's beautiful red-orange and brown wood is prized for any product, and massive trees could be used to make the ocean-faring wa'a, or Hawaiian canoes. The wood is especially resistant to exposure to sea water.

Juvenile, or the first young leaves produced by the koa tree seedling, are pinnately compound, having many small divisions of a single leaf.
Later, as the tree matures, an amazing transition occurs. The stem portion of the leaf, called the petiole, becomes larger and and wider. Eventually the mature tree produces only the leaves which are flattened and sickle-shaped, their origin primarily being from the petiole. Leaves produced in this way are called phyllodes. In this photo, several leaves are shown in this transistion

Their original development is speculated to be a response to drier climatic conditions in the past, which favored a such a leaf over the finely divided one which would lose more water.

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