Acacia koa A. Gray var. waimeae Hochr.

Scientific Name: Acacia koa A. Gray var. waimeae Hochr.

Classification: Plantae/ Tracheobionta / Spermatophyta / Magnoliophyta / Magnoliopsida / Rosidae / Fabales / Fabaceae / Leguminosae / Acacia Mill./ Acacia koa A. Gray var. waimeae Hochr.

<i>Acacia koa</i> A. Gray var. waimeae Hochr.
General Information
Usda SymbolACKOW
Life CyclePerennial
Growth HabitsTree
Native LocationsACKOW

Plant Guide

Use soil moisture sensors to measure the soil moisture of Acacia koa A. Gray var. waimeae Hochr..

Fact Sheet

Alternate Names

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


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.


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 , Use soil moisture sensors to measure the soil moisture of Acacia koa A. Gray var. waimeae Hochr..


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.


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. 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. After an overnight frost, young seedlings may be killed by rapid thawing caused by direct sunlight. The use of sun screens to slow thawing of seedlings is recommended. Young seedlings are intolerant of grass competition.


Overwatering and over-fertilization cause stress which often exhibits itself as yellowing of the leaves. Decreasing irrigation and eliminating nitrogen fertilizer can reverse the problem. Weed whacking the bark at the base of the tree can ruin the tree in a fraction of a second. It’s best to control weeds only by hand cutting and mulching near the tree. Leave a few inches of space against the trunk when mulching to reduce rotting. Root-bound seedlings that have become stunted in their containers will never return to being vigorous, healthy trees and should be discarded. Without adequate soil contact, newly planted seedlings can be severely set back or die within a few days of planting. When planting seedlings, especially those grown in forestry tubes, the soil should be firmed up against the seedling’s root system. Windy or shady conditions are not conducive to rapid growth. Trees should be protected from wind and given full sun most of the day. When planting dense stands of koa, failure to thin trees will cause growth to stagnate. The planting area must be fenced to exclude any grazing animals and competitive vegetation should be removed around planting holes. In urban situations, mulching with leafy materials is recommended to suppress weeds, conserve moisture, and protect koa’s surface roots. Pruning is not recommended since cuts provide easy access to fungi and borers.

Plant Traits

Growth Requirements

Temperature, Minimum (°F)31
Adapted to Coarse Textured SoilsYes
Adapted to Fine Textured SoilsYes
Adapted to Medium Textured SoilsYes
Anaerobic ToleranceNone
CaCO3 ToleranceMedium
Cold Stratification RequiredNo
Drought ToleranceMedium
Fertility RequirementMedium
Fire ToleranceMedium
Frost Free Days, Minimum365
Hedge ToleranceMedium
Moisture UseMedium
pH, Maximum7.0
pH, Minimum5.0
Planting Density per Acre, Maxim700
Planting Density per Acre, Minim300
Precipitation, Maximum200
Precipitation, Minimum50
Root Depth, Minimum (inches)30
Salinity ToleranceNone
Shade ToleranceIntolerant


Resprout AbilityYes
Shape and OrientationErect
Active Growth PeriodYear Round
C:N RatioLow
Coppice PotentialNo
Fall ConspicuousNo
Fire ResistantNo
Flower ColorYellow
Flower ConspicuousNo
Foliage ColorGreen
Foliage Porosity SummerModerate
Foliage Porosity WinterModerate
Foliage TextureMedium
Fruit/Seed ConspicuousNo
Nitrogen FixationHigh
Low Growing GrassNo
Leaf RetentionYes
Known AllelopathNo
Height, Mature (feet)110.0
Height at 20 Years, Maximum (fee100
Growth RateModerate
Growth FormSingle Stem
Fruit/Seed ColorBrown


Vegetative Spread RateNone
Small GrainNo
Seedling VigorMedium
Fruit/Seed Period BeginSpring
Seed Spread RateModerate
Seed per Pound4900
Propagated by TubersNo
Propagated by SprigsNo
Propagated by SodNo
Propagated by SeedYes
Propagated by CormNo
Propagated by ContainerYes
Propagated by BulbNo
Propagated by Bare RootYes
Fruit/Seed PersistenceYes
Fruit/Seed Period EndSummer
Fruit/Seed AbundanceMedium
Commercial AvailabilityRoutinely Available
Bloom PeriodSpring
Propagated by CuttingsYes


Veneer ProductYes
Pulpwood ProductNo
Post ProductNo
Palatable HumanNo
Palatable Browse AnimalHigh
Nursery Stock ProductYes
Naval Store ProductYes
Lumber ProductYes
Fodder ProductNo
Christmas Tree ProductNo
Berry/Nut/Seed ProductNo

<i>Acacia koa</i> A. Gray var. waimeae Hochr.