Acacia koa

Common Names

Koa, Koa Tree, Koai'a, Koai'e, Koa'oha

Summary

koa is a Hawaiian endemic evergreen tree native to six islands, typically 15–25 m tall with a 6–12 m canopy, often forming pure stands or co-dominant forests with ʻōhiʻa lehua; leaves are replaced by phyllodes and pale-yellow flowers appear in clusters, with seed pods 15–20 cm long containing 6–12 seeds; heartwood ranges from yellow to dark red-purple and is highly prized for furniture, cabinetry, veneers, and woodcraft; a nitrogen-fixer associated with Bradyrhizobium, it enriches soil and provides wildlife habitat; it tolerates well-drained soils in dry to moist forests from 100–2300 m elevation and is best planted above 610 m.

Cultivation and uses: requires well-drained soils, full sun to partial shade, and is shade-intolerant; tolerates drought but not salt- or waterlogged soils; spacing around 30–40 ft apart; rapid early growth around 5 ft per year; propagation mainly by seed after scarification or heat treatment, with seeds storing well and germinating in about 11–24 days; inoculation with rhizobia in nursery and field establishment; pruning discouraged; protect shallow roots from damage by mowing; uses include timber for furniture, cabinetry, veneers, and woodcraft, and as a tonewood for ukuleles and guitars, plus roles in restoration, erosion control, and wildlife habitat; potential pests and diseases include koa moth, koa psyllid, aphids, whiteflies, seed worms, seed weevils, rusts, and koa wilt; management emphasizes disease-free seed sources, sanitation, fencing to exclude grazing, and careful spacing and weed control

Lifecycle

Perennial

Height

20-115 ft

Spread

20-40 ft

Hardiness Zones

Zones 10-12

Sunlight Requirements

Ideally full sun; tolerates partial sun; partial shade for young plants.

Soil Type

Well-drained, deep loamy soil

Soil Drainage

Well-drained soils.

Soil pH

5.0-7.0

Bloom Color

Pale yellow

Bloom Time

Winter, peaks in late winter, may extend to early summer at lower elevations, and may occur year-round in some locations

Foliage Color

Green

Fall Foliage Color

No fall color; evergreen.

Leaf Lifecycle

Evergreen broadleaf

Growth Rate

Fast growth; about 1.5 m/year (≈5 ft/year) for the first ~5 years in favorable environments, then ~0.5 m/year thereafter.

Seasons of Interest

Spring, Summer, Fall, Winter

Propagation Methods

Seeds, Cuttings, Layering (air layering), Division, Tissue culture, Grafting, Root suckers

Attracts Wildlife

Bees, other pollinators, and birds are attracted.