Koa

Scientific Name: Acacia koa A. Gray

Koa

General Information
Usda Symbol	ACKO
Group	Dicot
Life Cycle	Perennial
Growth Habits	Tree
Native Locations	ACKO

Plant Guide

Use soil moisture sensors to measure the soil moisture of Koa.

Fact Sheet

Alternate Names

None A closely related species is ACKO2 - Acacia koaia: dwarf koa, koaie, koaoha, koai‘e, koaia

Uses

The primary use is for timber, though it creates wildlife habitat, and is an ornamental. Koa trees in natural ecosystems provide habitat for many plants, insects, and birds, some endangered, such as the ‘akiapōlā‘au (Hemignathus munroi), a species of honeycreeper. As a nitrogen-fixing species, koa plays an important role in forest fertility. A key traditional use of koa logs by early Hawaiians was to build canoes and make tools. Commercially, koa is the premier native timber of Hawai‘i and is one of the most expensive woods in the world. The leaves and ashes have been used medicinally by Hawaiians. Tannin from the koa bark has been used to make a red dye for traditional bark cloth. The name “koa” also means “warrior” in Hawaiian and is important culturally.

Status

Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).

Description and Adaptation

Adaptation

Adaptation

Koa is the largest native Hawaiian tree. It typically attains heights of 15-25 m (50-80 ft) with a canopy spread of 6-12 m (20-40 ft). Found between 100-2300 m (330-7500 ft). The form of trees ranges from an upright single trunk to low and sprawling with multiple trunks. Pale yellow flowers are borne in axillary racemes with spherical heads about 8.5 mm (0.33 in) in diameter. Flowers are produced throughout the year, peaking in mid to late winter. Seeds are contained within a pod (legume) 15-20 cm (6-8 in) long containing 6-12 seeds. There are three varieties of Acacia koa. A.koa var. koa, A.koa var. latifolia, and A. koa var. kauaiensis. Distribution: Endemic to the Hawaiian Islands. Please consult the Plant Profile page for this species on the PLANTS Web site.

Establishment

The only propagation method currently in wide use is from seed, Pods are ready to pick when their color has turned from green to brown or black, Growing koa seedlings is very similar to many other nitrogen-fixing tree species, requiring pre-germination treatment (scarification) to break through the hard, impermeable seed coat, inoculation with appropriate rhizobia bacteria, and special nutrient requirements, Trees should be inoculated in the nursery within 4 weeks of germination, Koa requires well-drained soils, Koa stands on shallow soils are not as productive as those on deep soils and may be short-lived, Koa is difficult to integrate with annual crops due to koa’s aggressive surface root system that competes with crops, while also susceptible to damage by human, animal, and machine traffic, Use soil moisture sensors to measure the soil moisture of Koa., Hawai‘i’s highly variable climate means that matching an appropriate seed source to the site conditions is important to foster a viable koa planting, Environmental tolerances of koa vary by population, Such variation is one reason that seedlings used in reforestation should come from seeds collected from sites near or similar to the planting site, Koa trees grow well only in the sun,