Acacia koa

 ( Koa ) 

Acacia koa, commonly known as koa, is a species of Flowering plant tree in the family Fabaceae. It is Endemism to the Hawaiian Islands, where it is the second most common tree. The highest populations are on Hawaii, Maui and Oahu.

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Name The name koa in the Hawaiian language ultimately comes from Proto-Austronesian * teRas meaning "core" or "ironwood"; many names referring to certain ironwood or heartwood species in Southeast Asia and Oceania such as Vitex parviflora ( tugás in Cebuano language), Eusideroxylon zwageri ( togas in Tombonuwo), and Intsia bijuga ( dort in Palauan language) descend from this root. The Hawaiian Acacia koa is closely related to a common tree in Taiwan called Acacia confusa. The two species also share a very similar appearance.

Koa also means brave, bold, fearless, or warrior.

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Description Koa is a large tree, typically attaining a height of and a spread of . In deep volcanic ash, a koa tree can reach a height of , a circumference of , and a spread of .

Anne Welsbacher (2025). 9780822546856, Twenty-First Century Books. . ISBN 9780822546856

It is one of the fastest-growing Hawaiian trees, capable of reaching in five years on a good site.

Kim M. Wilkinson (2025). 9780970254429, Permanent Agriculture Resources. . ISBN 9780970254429

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Leaves Initially, bipinnately compound leaves with 12–24 pairs of leaflets grow on the koa plant, much like other members of the Fabaceae. At about 6–9 months of age, however, thick sickle-shaped "leaves" that are not compound begin to grow. These are , blades that develop as an expansion of the leaf petiole. The vertically flattened orientation of the phyllodes allows sunlight to pass to lower levels of the tree. True leaves are entirely replaced by long, wide phyllodes on an adult tree.

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Flowers

of the koa tree are pale-yellow Sphere with a diameter of . Flowering may be seasonal or year round depending on the location.

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Fruit

Fruit production start occurring when a koa tree is between 5 and 30 years old. The fruit are , also called pods, with a length of and a width of . Each pod contains an average of 12 . The long, wide seeds are flattened Ellipse and range from dark brown to black in color. The pods are mature and ready for propagation after turning from green to brown or black. Seeds are covered with a hard seed coat, and this allows them to remain dormant for up to 25 years. Scarification is needed before A. koa seeds will Germination.

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Habitat

Koa is Endemism to the Hawaiian Islands of Hawaii, Molokai, Maui, Lanai, Oahu, and Kauai, where it grows at elevations of . It requires of annual rainfall. to neutral (Soil ph of 4–7.4) that are either an Inceptisols derived from volcanic ash or a well-drained histosol are preferred. Its ability to fix nitrogen allows it to grow in very young volcanic soils. Koa and ōhia lehua ( Metrosideros polymorpha) dominate the canopy of Hawaiian mixed mesic forests.

Alan C. Ziegler (2025). 9780824821906, University of Hawaii Press. . ISBN 9780824821906

It is also common in wet forests.

S. H. Sohmer (1987). 9780824810962, University of Hawaii Press. . ISBN 9780824810962

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Uses

koa's trunk was used by Ancient Hawaii Native Hawaiians to build waa (dugout )

William Alanson Bryan (2025). 9781444678208, Hawaiian Gazette Co, Ltd. . ISBN 9781444678208

and papa hee nalu (). Only paipo (Bodyboarding), kikoo, and alaia surfboards were made from koa, however; olo, the longest surfboards, were made from the lighter and more Buoyancy wiliwili ( Erythrina sandwicensis).

Ben Marcus (2025). 9780760327531, MBI Publishing Company. . ISBN 9780760327531

The reddish wood is very similar in strength and weight to that of black walnut ( Juglans nigra), with a specific gravity of 0.55, and is now sought for use in wood carving and furniture. Koa is also a tonewood, often used in the construction of ,

Gernot Rödder (2025). 9783802404467, Mel Bay Publications. . ISBN 9783802404467

,

Teja Gerken (2025). 9781890490218, String Letter Publishing. . ISBN 9781890490218

and Weissenborn-style Hawaiian . B.C. Rich used koa on some of their as well,

Ken Achard (1989). 9780933224186, Bold Strummer Ltd. . ISBN 9780933224186

and still uses a koa-Wood veneer topwood on certain models. Fender made limited edition koa wood models of the Telecaster and the Stratocaster in 2006. Trey Anastasio, guitarist for the band Phish, primarily uses a koa hollowbody Paul Languedoc guitar. Commercial silviculture of koa takes 20 to 25 years before a tree is of useful size.

Taylor, Collings and Martin are few among the many other brands that use that tonewood for manufacturing acoustic guitars.

In Hawaiʻi, the ‛umeke ‛ (Hawaiian: “wooden bowl”) has been a highly-perfected art form and considered a prized possession for well over a thousand years. They were expertly handcrafted using rare and exotic hardwoods like Kou, Milo, and Koa. Prior to 1819, ‛umekes were considered sacred and strictly reserved for ‛Ali‛i (Hawaiian: “Royalty”), and under penalty of death for a commoner to possess one. Today, ‛umekes are highly collectible and have become known as a universal symbol of generosity and welcome.American Woodturner --- Journal of the American Association of Woodturners volume 32, issue 5 – October, 2017, Feature Article, pgs. 45–51 “‘UMEKE LA‘AU: A RICH HAWAIIAN TRADITION”, Sharon Doughtie shares a well-researched account of the historical uses and nuances of Hawaiian bowls, or ‘umeke la‘au.

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Relation to other species

other Pacific Islands of volcanic (non-continental) origin, only Vanuatu has native Acacia species. A. heterophylla, from distant Réunion, is very similar and has been suggested to be the closest relative of koa. Genetic sequence analysis results announced in 2014 confirmed this close relationship; the estimated time of divergence is about 1.4 million years ago. A. heterophylla sequences nest within those of the more diverse A. koa, making the latter paraphyletic. Both species are thought to be descended from an ancestral species in Australia, presumably their sister species, Acacia melanoxylon. Dispersals most likely occurred via seed-carrying by birds such as . Both species have very similar , which differ from that of A. melanoxylon.

A closely related species, koaia or koaie ( Acacia koaia), is found in dry areas. It is most easily distinguished by having smaller seeds that are arranged end-to-end in the pod, rather than side by side. The phyllodes are also usually straighter, though this character is variable in both species. The wood is denser, harder, and more finely Wood grain than koa wood. Koaia has been much more heavily impacted by cattle and is now rare, but can be seen on ranch land in North Kohala.

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Conservation

The koa population has suffered from grazing and logging. Many wet forest areas, where the largest koa grow, have been logged out, and it now comes largely from dead or dying trees or farms on private lands. Although formerly used for , there are few koa remaining which are both large and straight enough to do so today. In areas where cattle are present, koa regeneration is almost completely suppressed. However, if the cattle are removed, koa are among the few native Hawaiian plants able to Germination in grassland, and can be instrumental in restoring native forest. It is often possible to begin reforestation in a pasture by disk harrowing the soil, as this scarifies seeds in the soil and encourages large numbers of koa to germinate. Experiments at the Hakalau Forest National Wildlife Refuge have shown that ōhia lehua ( Metrosideros polymorpha) survives best in pasture when planted under koa. This is because koa trees reduce radiative cooling, preventing frost damage to ōhia lehua seedlings.

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Ecology

Koa is the preferred host plant for the of the green Hawaiian blue ( Udara blackburni), which eat the flowers and fruits.

James A. Scott (1992). 9780804720137, Stanford University Press. . ISBN 9780804720137

Adults drink nectar from the flowers. Koa Plant sap is eaten by the adult Kamehameha butterfly ( Vanessa tameamea).

Susan Scott (1991). 9780935848939, Bess Press. . ISBN 9780935848939

The koa bug ( Coleotichus blackburniae) uses its rostrum to suck the contents out of koa seeds. Koa is vulnerable to infection by koa wilt.

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Gallery

File:Starr 070205 4082 acacia koa2.jpg File:Starr 060325-6745 Acacia koa.jpg File:Starr 041127-1178 Acacia koa.jpg File:Starr 051122-5287 Acacia koa.jpg File:Starr 060312-6710 Acacia koa.jpg File:Starr 041214-1500 Acacia koa.jpg File:Starr 040220-0316 Acacia koa.jpg File:Starr 040723-0533 Acacia koa.jpg File:Starr 030405-0136 Acacia koa.jpg File:Starr 041113-0733 Acacia koa.jpg File:Starr 051211-5686 Acacia koa.jpg File:Starr 030405-0092 Acacia koa.jpg File:Acacia koa with phyllode between the branch and the compound leaves.JPG| Acacia koa with phyllode between the branch and the compound leaves

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External links

• Photos of Acacia koa at Hawaiian Ecosystems at Risk Project (HEAR)
• UCLA botanical garden and home
• Historic photos and descriptions of Acacia koa

Categories: Koa, Endemic Flora Of Hawaii, Trees Of Hawaii, Least Concern Flora Of Oceania, Least Concern Flora Of The United States, Plants Described In 1854, Taxa Named By Asa Gray

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