Hawaiian Names with Diacritics
- Koa ʻohā
- Koa oha
- Dwarf koa
- Acacia koa
Did You Know ?
There are actually two species of koa native to Hawaiʻi. The large forest koa is well known around the world for the beautiful hard wood. Koa's smaller cousin, koaiʻa, that once grew in the lowlands of most of the main Hawaiian Islands, has an even harder wood that is much prized for its gnarled grain. But these trees are now rare and the wood is seldom seen in wood working.
Endangered Species Status
Plant Form / Growth Habit
Mature Size, Height (in feet)
- Tree, Small, 15 to 30
Mature Size, Width
Koaiʻa has a canopy spread of about 20 feet.
Long lived (Greater than 5 years)
- Provides Shade
- Specimen Plant
Additional Landscape Use Information
Koaiʻa is usually a better choice in the lowland urban landscape than koa because of its smaller stature, natural lowland dry habitat, drought tolerances, and more pest resistant properties than koa. [4,11]
Trees inoculated with rhizobia tend to be more vigorous. 
Additional Fragrance Information
Koaiʻa and koa have a distinctive aroma from the root area from a bacterium called rhizobia present in the soil and roots. An ammonia-like scent is given off during the nitrogen-fixing process. 
The pungent aroma is perhaps best appreciated by those who regularly work with this species. Otherwise, it generally has a non-appealing scent. [David Eickhoff, Native Plants Hawaiʻi]
Plant Produces Flowers
Additional Flower Color Information
Koaiʻa has light yellow fluffy round flower puffs.
Additional Blooming Period and Fruiting Information
Flowering and seed production can be sporadic but the peak blooming time is usually from January to March. The seed quality can be very poor in wetter climates but very high in drier climates.
Additional Plant Texture Information
Koaiʻa have sickle-shaped mature "leaves" called phyllodes, usually straighter and narrower than koa. The juvenile leaves (true leaves) are feathery compound leaves.
- Light Green
- Medium Green
Additional Leaf Color Information
Koaiʻa has green to gray green leaves.
Additional Pest & Disease Information
Koaiʻa seems to be less susceptible to Chinese rose beetles than koa, although it may be more prone to scale insects and mealybugs.
Koaiʻa (A. koaia) is also more tolerant than koa (A. koa) to diseases such as koa wilt. 
Since koaiʻa forms a symbiotic relationship with the bacteria in its roots for the nitrogen-fixing process, using pesticides around the root area is not recommended.
Seedlings can be fertilized 2 or 3 weeks after secondary growth with 8-8-8 or 10-10-10. Since koaiʻa are nitrogen-fixing trees, additional nitrogen is not necessary when phyllodes, or sickle-shaped leaves, begin to appear.
Trees should not be pruned unless necessary. Lower branches do self-prune. If pruning is required, it should be minimal, done properly and without excessive injury to the tree. 
Additional Water Information
Koaiʻa can tolerate both dry and moist watering conditions but do best under dry conditions. These small trees have light to moderate water needs. Once established, water once or twice a month in dry season. These xeric trees will not tolerate water-logged soil.
Soil must be well drained
- Full sun
- Partial sun
Additional Lighting Information
Trees do best in full sun.
Koaiʻa should be planted at least 20 feet apart.
These trees do not do well in very wet soils. Surface roots of koaiʻa will not tolerate high foot traffic, causing damage that will affect the health and vigor of the trees themselves.
Natural Zones (Elevation in feet, Rainfall in inches)
- 150 to 1000, 0 to 50 (Dry)
- 1000 to 1999, 0 to 50 (Dry)
- 2000 to 2999, 0 to 50 (Dry)
- 3000 to 3999, 0 to 50 (Dry)
Additional Habitat Information
The rare koaiʻa naturally grow in open, dry habitats. The Koaiʻa Tree Sanctuary in Kohala (Hawaiʻi Island) is an excellent place to see these trees in one of their last natural habitats. Many grow along the road to Waimea. Sadly, much of koaiʻa habitat has been converted to pasture. 
"Lānaʻi has very little koa," notes botanist George Munro. But "koaiʻa can be found widely scattered on the dry country." 
Given its natural range throughout the rest of the Main Islands, koaʻa may have possibly been found on Oʻahu in the past as well, though no specimens have been confirmed there.
Koaiʻa belong to the third largest plant family, the Pea or Legume family (Fabaceae). There are two endemic species of Acacia in the Hawaiian Islands: Acacia koaia and A. koa.
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.
The specific epithet koaia is from the Hawaiian word for this tree.
Koaiʻa and Koaiʻe are the given names for this species. Regarding Koaiʻe, it can figuratively mean a person or anything from the upland country. 
Koa ʻōha has been used for this species. Regarding this name, Hawaiian Dictionaries online provides this explanation for ʻohā: "n. Taro corm growing from the older root, especially from the stalk called kalo; tender plant (Isa. 53.3), shoot, sucker, branch (Isa. 11.2). Fig., offspring, youngsters (FS 235; cf. ʻohana). Also muʻu. See kalo for names of generations. Kai ʻohā, sea with small waves." 
These small trees are nitrogen-fixing and thus very beneficial to a healthy native Hawaiian environment. The growth of koaiʻa is due to the symbiotic relationship with a special bacteria called rhizobia that live in association with the root system. The bacteria convert, or fix, nitrogen from the air into usable nitrogen fertilizer for plants. The leaves, flowers and branches also provide nitrogen for understory plants in the area.
Some of the major physical differences between koa (Acacia koa) and koaiʻa (A. koaia) are:
- Koaiʻa are overall smaller and more compact trees with a denser, harder and more gnarled wood than koa.
- Koaiʻa usually have straighter and narrower phyllodes (expanded petioles) than koa.
- The seeds of koaiʻa are arranged in pods end-to-end (vertical) as opposed to a side-by-side (horizontal) arrangement with koa.
Otto Degener uses ʻakoa as an additional name for koaiʻa. 
Early Hawaiian Use
In general, the dense reddish brown wood is harder than koa and was used by early Hawaiians for short spears (ihe), long spears (pololū), fish lures (lāʻau melomelo), shark hooks (makau manō) with bone points, bait sticks in fishing, fancy paddles (hoe), house (hale) construction, ʻukēkē (musical bow), calabashes (ʻumeke),  and the ʻiʻe kūkū --the final beater to smooth out the kapa. [5,8]
Koaiʻa was not used for making canoes (waʻa) because it produced curly grained wood. 
One older source (Charles Gaudichaud,1819) states that Hawaiians "used all fragrant plants, all flowers and even colored fruits" for lei making. The red or yellow were indicative of divine and chiefly rank; the purple flowers and fruit, or with fragrance, were associated with divinity. Because of their long-standing place in oral tradition, the leaves and flowers of koaiʻa were likely used for lei making by early Hawaiians, even though there are no written sources. 
The crushed koaiʻa leaves were mixed with other plant materials and used in a steam bath for skin disorders.
Koaiʻa is sometimes seen in home and commecial landscapes. Hopefully, it will become a commonly used urban tree since it does so well in lower elevations.
Though the wood was apparently readily available to the early Hawaiians, only later in time was it used to make furniture. 
The phyllodes (sickle-shaped "leaves") are still used to make a nice lei. 
 "Growing Koa" by Kim M. Wilkinson, pages 11-12, 35-36, 39.
 "Hawaiʻi's Vanishing Flora" by Bert Y. Kimura, page 51.
 "Flora Hawaiiensis" by Otto Degener, Family: 169a Acacia Koaia
 http://www.hawaiibea.com/2006/02/koaiaa_monarch_.html#more [Accessed 11/ 22/08]
 "Plants in Hawaiian Culture" by Beatrice H. Krauss, pages 43, 45, 85.
 "Nā Lei Makamae--The Treasured Lei" by Marie A. McDonald & Paul R. Weissich, pages XIV-XV, 43.
 "The Strory of Lānaʻi" by George C. Munro, page 69.
 "Arts and Crafts of Hawaii" by Te Rangi Hiroa (Sir Peter H. Buck), page 169.
 "The Hawaiian Canoe" by Tommy Holmes, page 23.
 http://wehewehe.org [Accessed 8/10/10]
 "Pests and Diseases of Acacia Koa" by J. B. Friday in "Hawaii Landscape" Sept./Oct. 2013, page 24.
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Other Nursery Profiles for Acacia koaia