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Plant Profile

Koai'a (Acacia koaia)

Closeup on phyllodes (expanded petioles) replacing the leaves and seed pods (brown colored). Photo Credit: K. Wood
  • Global Rank: G2 - Imperiled
  • Legal Status: N/A
  • Family: Fabaceae
  • State: HI
  • Nature Serve ID: 153691
  • Lifeform: Tree
  • Date Inducted in National Collection: 05/28/1986

Species that belong to the genus Acacia are member of the family Fabaceae, which is also commonly referred to as the legume, or pea, family. There are two Acacia species endemic to Hawaii. The first, referred to as Acacia koa sensu stricto, is a fairly common Hawaiian tree that is well known for its decorative wood. The other, A. koaia, is a rare tree that is adapted to drier conditions and has harder wood, a smaller stature, and more gnarled appearance than its more common relative. A. koaia can be locally abundant in drier habitats, but this habitat is seriously threatened (K. Wood pers. comm. 2002). This rare tree has sickle-shaped leaves that are actually phyllodes, or flat, expanded petioles that take the place leaf blades & perform the same functions. The flowers are formed in heads with cream-colored corollas, long, curled stamens (more than twice the length of the corolla) and pubescent ovaries. (Wagner et al. 1999) To distinguish between the common and rare species, a number of characteristics can potentially be used. A. koaia pods are laterally flattened with longitudinally arranged seeds, narrower pods and straighter phyllodes than A. koa sensu stricto which has wider pods, laterally arranged seeds, and more curved phyllodes. A confounding problem has arisen because, on the northern coast of Kauai, a population of Acacia spp. has been found with the habit and phyllodes of A. koa sensu stricto but with the pods of A. koaia (Wagner et al. 1999).

Where is Koai'a (Acacia koaia) located in the wild?


A. koaia is found in low elevations in drier, open woodland habitats (Wagner et al. 1999). Associated species for A. koaia include Dicranopteris linearis (uluhe), Pandanus tectorius (hala), Bidens forbessii (no common name), Hibiscus kokio subsp. saintjohnianus (Kokio ulaula), Lipochaeta connata var. acris (nehe), Pleomele aurea (Halapepe), and Metrosideros polymorpha (Ohia) (Wagner et al. 1990).


A. koaia is found on Kauai, Oahu, Molokai, Lanai, Maui and Hawaii (USFWS 2001).

States & Provinces:

Koai'a can be found in Hawaii

Which CPC Partners conserve Koai'a (Acacia koaia)?

CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.

Conservation Actions

Nature Serve Biotics
  • 05/02/2017

Acacia koaia is endemic to the Hawaiian Islands. It has been recorded from the islands of Kauai, Oahu (a recent find, possibly planted), Molokai, Maui, Lanai, and Hawaii. Acacia koaia is or was a dominant tree in certain areas. However, over most of its range its distribution is very spotty, with patches of trees widely separated. Many of these patches are the result of root suckering. Sexual reproduction appears to be uncommon in many areas. The number of individual clones in existence may still number several thousand. Because Acacia koaia occurs at relatively low elevations, and often close to inhabited areas, it has been severely impacted by ranching, agriculture and human-ignited fires. Other threats to the species are feral goats and pigs, deer, and invasive alien plants.

  • 01/01/2010

Threats to A. koaia include habitat degradation and herbivory by goats, and invasion of habitat by alien plant species. Because it occurs in low elevations, it has been severely impacted by historic ranching, agriculture and human-caused fires. (NatureSer

  • 01/01/2010

Number of populations: many (USFWS 2001) Number of plants: >1000 (USFWS 2001)

  • 01/01/2010

Seeds of A. koaia have been tested by the National Seed Storage Laboratory (NSSL), finding that they are orthodox and tolerant to drying and freezing. The laboratory germination time was four months (Yoshinaga 2002).

  • 01/01/2010

Judy and Will Hancock are assisting the Hawai'i Forest Stewardship Program (Kalopi Dryland Forest Restoration) in restoring the ridges of Kohala (Hawaii). They have been planting A. koaia on the leeward side of the Kohala Mountains since 1989 and claim that the shorter A. koaia are better adapted to the windy, dry Kohala landscape. The goal of the Kalopi project is primarily to restore native Hawaiian dryland forest. However, any wood from harvest from dead or thinned trees is valued for its beautifully grained wood (Hawaii Forestry News 2000). The National Tropical Botanical Garden (NTBG) currently has ex situ holdings of 204 seeds in its seed bank, which represents four populations. In addition, 100 individuals from four populations are growing in the botanical garden.

  • 01/01/2010

1. Genetic studies are needed to confirm taxonomic and the phylogenetic status of A. koaia. 2. Genetic studies are also needed to confirm the distinctiveness between island populations. 3. Map genetic diversity in the surviving populations of A. koaia. 4. Test management strategies on invasive species and pest control for A. koaia. Recommendations derived from M.H. Chapin, M. Maunder, and Wagner et al. (1999).

  • 01/01/2010

1. Establish a full seed bank collection of A. koaia representing all available populations. 2. Development of proper horticultural protocols including pest management for A. koaia. 3. Survey ex situ holdings and conduct molecular fingerprinting. Recommendations derived from M.H. Chapin and M. Maunder.


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Taxon Acacia koaia
Authority Hillebr.
Family Fabaceae
CPC Number 17
ITIS 182080
Duration Perennial
Common Names koai'a | koai'e | koa'oha
Associated Scientific Names Acacia koaia
Distribution A. koaia is found on Kauai, Oahu, Molokai, Lanai, Maui and Hawaii (USFWS 2001).
State Rank
State State Rank
Hawaii S2
Ecological Relationships

Common Name Name in Text Association Type Source InteractionID
Bees Confirmed Pollinator Link
Bees Confirmed Pollinator Link
Flies Confirmed Pollinator Link
Lead Institution State Reintroduction Type Year of First Outplanting
Hawaii Division of Forestry and Wildlife Hawaii Reintroduction 2014
Hawaii Division of Forestry and Wildlife Hawaii Reintroduction 2016

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