Acacia koaia
Fabaceae or Pea family [Nature Clearly]
Synonyms: none
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Koaiʻa
Koaiʻe, Koa ʻohā
Dwarf koa
Natural Range & Environment
Acacia koaia is endemic to the dry forests and open scrub/grasslands on Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi Island, where it is considered Vulnerable [Wagner et al. 1990]. "Lānaʻi has very little koa," notes botanist George Munro. But "koaiʻa can be found widely scattered on the dry country." [Munro 2007.]
The small stature of koai‘a, characteristic leaves and end-to-end seed pod arrangement are among the features that distinguish it from its larger cousin, koa (Acacia koa).
Description
Koai‘a are small, rare, endemic trees growing to under 6 m (20 ft) tall and canopy spread. Koai‘a is fairly fast-growing in cultivation. The small pom-pom-shaped cream to yellow flowers are abundant during their peak blooming period from January to March.
Grayish-green, sickle-shaped, mature "leaves" called phyllodes are usually straighter and narrower than koa. The juvenile leaves (true leaves) are feathery compound leaves looking much like koa haole.
Koai‘a seed pods are narrower than koa pods, and the seeds are arranged end-to-end or vertically, as opposed to side-by-side (horizontal) with koa.
Growth Requirements
General
Compared to koa, koaiʻa is a superior choice for lowland urban landscapes due to its smaller size, natural habitat in dry lowlands, and resistance to pests. Additionally, it is highly tolerant of heat, wind, and drought conditions.
For optimal growth, koaiʻa thrives in full sun and well-drained soil. Once established, it requires minimal watering. Koaiʻa is nitrogen-fixing and does not need additional fertilizers. (see Special Features and Information - General) However, it cannot tolerate waterlogged soil. It is important to avoid heavy foot traffic around the tree, as the surface roots are easily damaged. Prolonged exposure to excessive traffic can impact the overall health and vitality of the tree.
Pests and Diseases
Koaiʻa may be affected by Koa wilt. See Growth in the Garden and Diseases & Pests in Native Hawaiian Garden. Refer to the Pests & Diseases page for additional treatments.
Uses
Ancient Hawaiian
The dense reddish-brown wood of koaiʻa is known for its hardness, making it a valuable resource for early Hawaiians. They utilized this wood for a variety of purposes, including crafting short spears (ihe), long spears (pololū), fish lures (lāʻau melomelo), shark hooks (makau manō) with bone points, bait sticks for fishing, decorative paddles (hoe), house (hale) construction, musical bows (ʻukēkē), calabashes (ʻumeke), and ʻiʻe kūkū - the final beater used to smooth out kapa [Krauss 1993].
Despite its durability, koaiʻa was not suitable for making canoes (waʻa) due to its curly-grained wood [Holmes 1981]. According to an older source (Charles Gaudichaud, 1819), Hawaiians incorporated fragrant plants, flowers, and colored fruits into lei-making. Red and yellow hues symbolized divine and chiefly status, while purple flowers and fragrant fruits were associated with divinity.
Although there are no written sources, koaiʻa leaves and flowers likely played a role in lei making, given their significance in oral tradition [McDonald & Weissich 2003]. Medicinally, crushed koaiʻa leaves were combined with other plant materials and used in steam baths to treat skin disorders.
Modern
Although wood was readily available to early Hawaiians, it was not until more modern times that it began to be utilized for furniture making. The phyllodes, or sickle-shaped leaves, are still commonly used to create beautiful lei [McDonald & Weissich 2003].
Special Features and Information
General
Koaiʻa are members of the Pea or Legume family (Fabaceae), which is the third largest plant family. There are two species of Acacia that are endemic to the Hawaiian Islands: Acacia koaia and A. koa.
These trees play a crucial role in maintaining a healthy native Hawaiian environment due to their ability to fix nitrogen. This process is made possible through a symbiotic relationship with a special bacterium known as rhizobia, which live in association with the tree's root system. The bacteria convert nitrogen from the air into a usable form that acts as a natural fertilizer for plants, benefiting the growth of nearby vegetation. Trees inoculated with rhizobia tend to be more vigorous [Wilkinson & Elevitch 2003].
In addition to their nitrogen-fixing abilities, the leaves, flowers, and branches of koaiʻa also provide essential nutrients for understory plants in the surrounding area. This makes them a vital component of the ecosystem, supporting the overall biodiversity.
Hawaiian Name
The species is known by the given names koaiʻa and koaiʻe. Koaiʻe, in particular, is a term that can figuratively represent a person or anything associated with the upland country [Hawaiian Dictionaries].
Etymology
The generic name Acacia is derived from the Greek akakia, the name for Acacia arabica, ultimately from akis or ake, a Greek word meaning "a sharp point" and referring to the thorns of this particular plant [Gledhill 2008].
Though no reference has been located thus far, there is little doubt that the specific epithet koaia is from the Hawaiian name for this tree.
DWE
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