Acacia koaia
Genus
Acacia
Species
koaia
Hawaiian Names with Diacritics
- Koa ʻohā
- Koaiʻa
- Koaiʻe
Hawaiian Names
- Koa oha
- Koaia
- Koaie
Common Names
- Dwarf koa
Synonyms
- Acacia koa
Distribution Status
Endemic
Endangered Species Status
At Risk
Plant Form / Growth Habit
- Tree
Mature Size, Height
- Tree, Small, 15 to 30
Mature Size, Width
Koaiʻa has a canopy spread of about 20 feet.
Life Span
Long lived (Greater than 5 years)
Landscape Uses
- Provides Shade
- Screening
- Specimen Plant
Plant Produces Flowers
Yes
Flower Type
Not Showy
Flower Colors
- Cream
- Yellow
Additional Flower Color Information
Koaiʻa has light yellow fluffy round flower puffs.
Blooming Period
- Sporadic
- January
- February
- March
Additional Blooming Period 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.
Plant texture
- Coarse
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.
Leaf Colors
- Light Green
- Medium Green
Additional Leaf Color Information
Koaiʻa has green to gray green leaves.
Source of Fragrance
No Fragrance
Additional Fragrance Information
Koaiʻa have a distinctive pungent smell that is emitted from the symbiotic bateria in the root and soil area.
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.
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.
Fertilizer
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.
Pruning Information
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. [4]
Water Requirements
Dry
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
Yes
Light Conditions
- Full sun
- Partial sun
Additional Lighting Information
It does best in full sun.
Spacing Information
Koaiʻa should be planted at least 20 feet apart.
Tolerances
- Drought
- Wind
Soils
- Clay
- Cinder
- Organic
Limitations
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
- 150 to 1000, 0 to 50
- 1000 to 1999, 0 to 50
- 2000 to 2999, 0 to 50
- 3000 to 3999, 0 to 50
Natural Range
- Kauaʻi
- Oʻahu
- Molokaʻi
- Lānaʻi
- Maui
- Hawaiʻi
Additional Growth Environment 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. [2]
Its former natural range extended possibly on Oʻahu as well.
Special Notes and Information
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.
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 and plants in the area.
Some of the major physical differences between koa and koaiʻa 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. [3]
Early Hawaiian Use
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 melomeleo), 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]
The crushed koaiʻa leaves were mixed with other plant materials and used in a steam bath for skin disorders.
Modern Use
The phyllodes can be woven together to make a very attractive lei. [Rick Barboza, Hui Kū Maoli Ola]
The very prized wood is scarce today and rarely used.
Landscape Use
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] Trees inoculated with rhizobia tend to be more vigorous. [1]
Additional References
[1] "Growing Koa" by Kim M. Wilkinson, pages 11-12, 35-36.
[2] "Hawaiʻi's Vanishing Flora" by Bert Y. Kimura, page 51.
[3] "Flora Hawaiiensis" by Otto Degener, Family: 169a Acacia Koaia
[4] http://www.hawaiibea.com/2006/02/koaiaa_monarch_.html#more (accessed November 22, 2008)
[5] "Plants in Hawaiian Culture" by Beatrice H. Krauss, pages 43, 45, 85.
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