Koa: Hawaii's Majestic Endemic Acacia

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• Family:	Mimosaceae
  Genus:	Acacia (a-KAY-see-uh) (Info)
  Species:	koa

Overview

Koa (Acacia koa) is the **largest, most iconic, and culturally significant endemic tree of the Hawaiian Islands**. Once dominating vast montane forests on all major islands, it is now reduced to fragments but remains the **premier Hawaiian timber tree**—its wood revered for its beauty, workability, and connection to Hawaiian heritage (canoes, surfboards, ukuleles, furniture).

Form, Phyllodes & Flowers

A **large, fast-growing evergreen tree**, 50–100+ feet tall with a broad, spreading canopy. The "leaves" are **phyllodes (modified petioles)**: **sickle-shaped, 3–9 inches long, thick, gray-green**, with parallel veins. True bipinnate leaves appear only on seedlings. **Pale yellow, powder-puff flower heads** (1/2 inch) bloom in axillary clusters, often after rain. Pods are flat, 6–12 inches, splitting to release dark seeds.

Wood: The Hawaiian Mahogany

The heartwood is **rich, variable reddish-brown to golden, with spectacular figuring (curl, fiddleback, quilt)**. It is **moderately dense, stable, and works beautifully**—the wood of choice for **koa canoes (wa'a), ukuleles, guitars, fine furniture, and turnings**. It is one of the world's most valuable specialty woods.

Ecology, Culture & Conservation

Koa is a **nitrogen-fixing pioneer** on lava flows and disturbed sites, creating soil for later successional species. It supports unique native birds (e.g., 'Akiapōlā'au). **Threats:** logging, grazing (cattle destroy seedlings), invasive grasses, rats, and disease (koa wilt). **Conservation:** active reforestation, fencing, and sustainable forestry initiatives aim to restore koa forests.

Cultivation

**USDA Zones 10–11 (tropical highlands).** **Full sun; well-drained, acidic volcanic soil; cool nights; moderate rain.** Difficult outside Hawaii due to specific climate needs. A tree of **profound ecological and cultural mana**—planting koa in Hawaii is an act of restoration and legacy.