Family: Fabaceae

Koa is a large native tree endemic to Hawaiʻi. Along with ʻōhiʻa, koa dominates the upper levels of the native forest. It can grow to massive proportions, more than 100 feet tall with a diameter of over three feet. A standout tree, koa radiates a silver-green hue off its sickle-shaped leaves. However, these are not true leaves. Instead, koa produces pinnately compound leaves as a juvenile, which are shed with age, and their stem (phyllodes) flattens out. Flowers are cream to yellow and shaped like powder puffs.

A member of the pea family (Fabaceae), koa is a nitrogen-fixing tree. It grows rapidly, up to 5 feet a year. Koa shares the Acacia genus with the endemic koaiʻa. Compared to koa, koaiʻa are generally smaller, have straighter phyllodes, and their seeds are arranged end-to-end within seedpods instead of side-by-side like koa.

Habitat & Uses

Koa is endemic to most of the main Hawaiian Islands within dry and mesic forests. It can be found growing between 300-7,000 feet in elevation.  However, this species does better at higher elevations (above 2000 feet). Koa is a keystone species of the forest as it supports and provides habitat for many native insect, wildlife, and plant species.

Koa was the most valuable tree in Hawaiian society. Of upmost significance is the use of koa for waʻa (canoe) for voyaging, fishing, and other oceanic travel. The bark was used for red dye, leaves can be added into lei, and different parts of the koa were utilized in traditional medicine. Commercially today, koa is one of the most expensive woods in the global market. Woodworkers transform this tree’s beautiful wood into furniture, instruments, urns, jewelry, accessories, crafts, and decor.

Landscaping & Cultivation

Grow your koa in full sun and give your tree 30-40 feet of space from other trees so it can grow to its fullest potential. Koa reaches heights of over 100 feet in a healthy forest, but it will more than likely reach a maximum of 20-30 feet in urban and low elevation landscapes. It is essential not to wound the trees as koa, especially at lower elevations, are very susceptible to certain diseases. Weedwhackers and other lawn equipment can ding the tree and create a gaping hole, a place for diseases to enter the tree. Also, keep pruning to an absolute minimum. Germination can be done from seed with the help of scarification and soaking.

Koa likes to be planted with many friends like naio (Myoporum sandwicense), lonomea, kōlea, kōpiko (Psychotria hawaiiensis), ʻiliahi (Santalum freycinetianum), olopua, māmaki, pilo (Coprosma rhynchocarpa), hāpuʻu, and palapalai. All of these companion plants benefit from the nitrogen-fixation of koa. Unfortunately, koa also has many pests to lookout for, including: psyllids, black twig borers, aphids, whiteflies, Chinese rose beetles, sand weevils, koa seed worms, mealybugs, root knot nematodes, and various fungi and rusts. However, please do not use pesticide around the root area of koa trees. Pesticides could harm the symbiotic bacteria responsible for fixing nitrogen.

Name Origins

The genus name Acacia is from the Greek akis or ake meaning sharp point and refers to the thorns of the Acacia arabica. The species name koa can mean brave, bold, fearless; warrior, fighter in ʻŌlelo Hawaiʻi. The use of koa for canoes generates a physical embodiment of the meaning behind koa. As you had to be fearless and steadfast to voyage upon the powerful moana (ocean). Similar to the koa (warriors) who went to war with koa weapons.

Plant Uses:

• Cultural significance
• Erosion control
• Lei flower
• Medicinal
• Nitrogen fixer
• Ornamental
• Privacy / screening
• Shade
• Specimen
• Woodworking

Plant Dangers:

• No dangers