Koa is endemic to Hawai'i; it does not grow naturally anywhere else in the world. It is a fast growing tree, adding as much as an inch in diameter and two feet in height per year. When found in old forests fighting other trees for light it will grow tall and relatively straight, up to 100 feet tall, with a base diameter up to five feet. Such trees were prized by Hawaiians for carving canoe hulls. At the edge of a forest or on its own koa will likely retain its lower branches, grow to shorter heights with a broad canopy, and develop a crooked trunk with numerous crotches and a diameter of up to seven feet.
Almost all present-day commercial koa harvesting is done on the island of Hawai'i. You will find koa growing from 1,000 to over 7,000 feet above sea level, thriving in the 2,500-6,000 foot range. This is the range where many cattle ranches were established 100-150 years ago. At that time hundreds of thousands of acres of native koa forests were destroyed by the introduction of cattle. Koa is a member of the legume family and its seedlings are to cattle (or feral pigs or goats) like candy is to kids. Thus little or no reforestation occured naturally on cattle ranches or where feral mammals roamed. While native Hawaiians had cleared some of the lowland forests, as the traditional kapu laws were dismantled in the 1800's much of the native koa forest died off due to logging and clearing for cattle ranches.
At present, logging on state-owned conservation lands is prohibited, though midnight logging (illegal logging) is a persistent problem on such lands. Due to the relatively small number of acres remaining and the high demand for this sought-after wood, the supply of koa is limited and the cost is high. There is growing interest in replanting koa [don't worry, this is our only pun], and an estimated 15,000-20,000 acres have been planted in koa in the past 20 years. Some landowners find that they only need to fence the land to keep cattle and other animals off. Because the seeds lay dormant for 50-75 years, the koa trees will sprout up and establish themselves fairly quickly on their own. Often the land is scarified--i.e., scraped with a bulldozer--to expose the dormant seeds.
At Notable Woods, we only buy from loggers and ranches who are doing clean-up logging of dead and dying trees. Many in the industry recognize that it is essential to leave healthy seed stock and a functioning eco-system in place. There are about 50 native plants and animals whose life cycles are completely dependent upon the koa tree--and upon whose existence the koa tree depends. When koa forests are wiped out so too are these species, and the problems found in some reforestation projects are thought to result from the disrupted eco-system.
For more information of koa, check out Growing Koa by Wilkinson and Elevitch. This book was published in 2003, and appears to be the bible of koa. While it paints a dark picture of what we have done to the koa forests it paints a bright picture of recent efforts to re-establish koa as the proud, abundant tree it once was.
Koa is a medium-density hardwood. Its density varies, but averages 42 pounds per cubic foot when air-dry, with an average specific gravity of .60, oven-dry. Its color ranges from light to dark brown; sometimes displaying dark brown-to-purple striping. It generally shows a golden luster or irredescence when finished. It is an open pore wood with relatively small pores. Medullary rays are fine; with good eyes you will sometimes see the rays on perfectly quartersawn wood.
As with its color and grain, koa's density can vary from tree to tree. Koa is very similar to black walnut in a) density, b) stability, and c) strength and stiffness. Both koa and walnut are stable due to relatively equal shrinkage along radial and tangential planes. With the exception of crotch or defect wood, it can be dried and seasoned without special procedures, and generally without degrade. It takes edge tools, sanding and finishes well. Few will deny its beauty as a finished wood.
Koa has established itself as a sought-after tonewood in the past ten years. While it has been the principle wood used in 'ukulele construction during the past 100 years, its recent popularity results in good part from its use by the leading guitar factories. Martin, Taylor, Breedlove, Larrivee, Tacoma, Santa Cruz, and Collings all offer koa models.
In general, our instrument hardwoods are graded by the degree of figure present. Borderline grades get bumped up or down depending on the presence of color and striping, and depending on how well it is quartersawn. We sell sets that have non-structural flaws within the pattern area; these 2nds follow the grading below but are discounted due to the defect.
From time-to-time we have Master Grade koa which is "off-the-charts" because of its rare, exceptional color and curl. Instrument-quality koa is found in, say, one of ten logs, and the rarest master grade is found in only one of ten or twenty of those instrument logs.
Check out our Gallery page for photos of koa sets. Our general grade guidelines: