Hawaiian Names with Diacritics
- Acacia hawaiiensis
- Acacia heterophylla var. latifolia
- Acacia kauaiensis
- Racosperma kauaiense
- Racosperma koa
Did You Know ?
Koa is the largest native tree in the Hawaiian Islands reaching heights of about 115 feet (33 m)! Commercially, koa is one of the most expensive woods in the world. It is used to make furniture, veneer, and crafts. Most koa is harvested from remnant individuals or stands in pasture lands. 
Endangered Species Status
Plant Form / Growth Habit
Mature Size, Height (in feet)
- Tree, Small, 15 to 30
- Tree, Medium, 30 to 50
- Tree, Large, Greater than 50
Mature Size, Width
Koa can have a canopy spread of 40 feet or more. But typically, with a canopy spread of 20-40 feet. 
Long lived (Greater than 5 years)
- Erosion Control
- Provides Shade
Additional Landscape Use Information
Koa are fast growing trees at 5 feet per year for the first five years, and can reach impressive heights in several decades in upper elevation landscapes.  Though koa can grow at lower elevations, some varieties may succumb to diseases after a decade of growth. Since there is so much variety in koa habit from shrubby, multi-branched forms to tall straight trees, it is good to inquire of the source so as to suit your landscaping needs.
While koa can grow to heights of over 100 feet in their natural undisturbed environment, it would take many decades, if ever, to reach such heights in the urban landscape. They are more likely to grow to about 20 to 30 feet in the landscape at low elevations. [Rick Barboza, Hui Kū Maoli Ola]
Growth is in virtue of symbiosis with special bacteria called rhizobia that live associated with the roots. The bacteria convert, or fix, nitrogen from the air into usable nitrogen fertilizer for plants. The leaves, flowers and branches also provide nitrogen for understory and plants in the area. Koa inoculated with rhizobia tend to be more vigorous trees. 
Recommended planting is above 2000 feet [610 m]. 
Koa are easily damaged by lawnmowers and gas trimmers, a.k.a. "weed wackers." J. B. Friday, Extension Forester with the University of Hawaiʻi Cooperative Extension Service, comments that once koa injured, "rot tends to set in and the trees day are numbered." How to prevent unnecessary injury for these fragile trees? J. B. says that "a wide band of mulch and keep weed-eating implements away." 
J. B. Friday concludes an article with encouraging words for planting koa. He states: "Although koa may only live 5 to 20 years in urban lowland settings and never develop into the huge spreading tree seen in the forest, there is still educational value in planting this endemic tree. At schoolyard or demonstration plantings especially, generations of children will be able to see what koa [is] and develop a connection with our forests." 
Koa look nice when planted with other native plants such as naio, lonomea, kōlea, kōpiko, ʻiliahi, olopua, and māmaki, pilo, hāpuʻu, and palapalai.* These plants also beneift from the nitrogen-fixation by koa.
* These plants can be found on this website using the "Browse Plants" feature found at the top. Enter plant names without diacritics.
Additional Fragrance Information
Koa and koaiʻa have a distinctive aroma from the root area from a bacterium called rhizobia present in the soil and roots. An ammonia-ilke scent is given off during the nitrogen-fixing process. 
The pungent aroma is perhaps best appreciated by those who regularly work with this species. Otherwise, it generally has a non-appealing scent. [David Eickhoff, Native Plants Hawaiʻi]
Plant Produces Flowers
Additional Flower Color Information
Light yellow, cream or white round powder puff flowers. Showy displays when seen en masse.
Additional Blooming Period and Fruiting Information
Flowering occurs most heavily from January to March and into May with seeds ripening in August, September and October and persistent year round. 
Additional Plant Texture Information
Leaves are 2 to over 10 inches long. Koa have sickle-shaped mature "leaves" called phyllodes, which are the main photosynthetic organs. Juvenile leaves, the true leaves, are feathery compounds.
- Light Green
- Medium Green
Additional Leaf Color Information
Koa leaves are green to gray green.
A large-leaved koa form was known as koa lau nui. 
Additional Pest & Disease Information
Koa is known to attract aphids, whiteflies, Chinese rose beetles, seed weevils (Aracerus levipennis, Stator spp.), koa seed worm (Cryptophlebia illepida), koa moth,* mealybugs, root knot nematodes (Meloidogyne spp.), and a stem boring grub are also known to infest plant.
A serious pest attacking koa in lower elevation is the black twig borer (Xylosandrus compactus, Xyloborus spp.). Periodic pruning and removal of infected twigs is a best management program for this pest. [16,22]
The Acacia psyllid (Acizzia uncatoides) can greatly infest koa plantations resulting in branchy, poorly formed trees. 
Since koa forms a symbiotic relationship with bacteria in the roots for the nitrogen-fixing process, it is recommended that pesticides not be used around the root area.
Several fungi (Fusarium oxysporum, F. solani, Calonectria spp.), root rot (Armillaria spp. Pythium sp.), and rusts (Ateloclauda spp., Endoraecium spp.) on phyllodes are known infect koa. Native rusts (e.g., Ateloclauda digitata) may cause deformation and "witches broom" but are not fatal. Older trees are also attacked by a number of wood-rotting fungi.  There are indeed a number of pests and diseases that affect koa, but perhaps Koa wilt is one of the more serious often resulting in the death of the plant. 
Some native mistletoes or hulumoa (Korthalsella spp.) also parasitize koa. 
* J. B. Friday, earlier mentioned, notes that "an outbreak of the koa moth (Scotoythra paludicola) on the Big Island in 2013 reminded koa growers of the damage potentially caused by this native insect, which defoliated tens of thousands of acres of koa... Fortunately, outbreaks of the koa moth rarely occur." He says that "damaged or multiple leaders or malformed brances can be pruned if caught early enough so that they can be removed by clipping. Once branches have grown enough to require a saw for removal, it is probably too late to prune them, as wounds of koa trees allow entry of wood-rotting fungi." 
Lightly fertilize seedlings 2 or 3 weeks after secondary growth. Since koa are nitrogen fixing trees, additional nitrogen is usually not necessary.
Pruning koa often does more harm than good. Wounds from pruning may not heal, exposing the heartwood to rot and greatly increases their suspeceptability to disease and pests. Additionally, pruning slows the growth of the trees. Therefore, koa should not be pruned if it can be avoided. Lower branches do self prune. If pruning is needed, it should be absolutely minimal, done properly, and without excessive injury to the tree. [1,16]
Koa seedling roots should not be pruned, trimmed, or otherwise "fluffed out."
Additional Water Information
Water once a month during dry months, more often for "coastal" trees.
Soil must be well drained
- Full sun
- Partial sun
Additional Lighting Information
Koa does best in full sun.
Trees should be spaced 30 to 40 ft. apart.
Koa are not tolerant of salty soils, infertile soils, constant waterlogged soils, constant high winds, or shade. [1,16] Trees can tolerate drought for 3-5 months, depending on soil, compettion for weeds, relative humility, winds, and other factors. 
Koa prefer soils that are loamy, sandy* clay forms, clays, clay loams, and sandy clays. Koa natural occur on both light, ash-derived soils and on highly weathered clays on older islands. Organic soils on lava rock are common in many koa regions. 
Surface roots are easily damaged with high human, animal, and machine traffic. [1,16]
* Salt-free sands.
Natural Zones (Elevation in feet, Rainfall in inches)
- 150 to 1000, 0 to 50 (Dry)
- 150 to 1000, 50 to 100 (Mesic)
- 1000 to 1999, 0 to 50 (Dry)
- 1000 to 1999, 50 to 100 (Mesic)
- 2000 to 2999, 0 to 50 (Dry)
- 2000 to 2999, 50 to 100 (Mesic)
- 3000 to 3999, 0 to 50 (Dry)
- 3000 to 3999, 50 to 100 (Mesic)
- 4000 to 4999, 0 to 50 (Dry)
- 4000 to 4999, 50 to 100 (Mesic)
Additional Habitat Information
Though not as common as in the past, koa is still easily found in suitable habitat often a dominant component of native and alien mixed forests. Koa grows in dry to moist forests from 300 to 7,000 feet, occasionally as low as 80 feet and rarely as high as 8,000 feet. 
There are three varieties of koa. Acacia koa var. kauaiensis on Kauaʻi; var. latifolia on Hawaiʻi Island; and var. koa occurs on all the main islands. 
Koa trees with characteristics in between koa (Acacia koa) and koaiʻa (A. koaia) occur on Kauaʻi. 
Koa belongs to the third largest plant family, the Pea or Legume family (Fabaceae). There are two endemic species of Acacia in the Hawaiian Islands: Acacia koa and A. koaia.
Koa resemble their smaller cousins koaiʻa, but there are some significant differences. (See Acacia koaia "Special Notes and Information")
The generic name Acacia is derived from the Greek, akakia, the name for Acacia arabica, ultimately from akis or ake, a Greek word meaning a sharp point and referring to the thorns of this particular plant.
The specific epithet koa is the Hawaiian name for this species of tree.
Koa means "brave, bold, fearless" and also "warrior, fighter."
Koa are dominant trees in Hawaiian forests and provide suitable habitat for many native species birds. The aptly named Koa-finches, Rhodacanthis palmeri and R. flaviceps, fed almost exclusively on green koa seed pods, sometimes the entire pod in pieces or occasionally only the seeds. Sadly, these brilliantly colored honeycreepers are now extinct. 
Koa varies greatly from one location to another. For this reason and others, it is important that koa, or any other native plants from nurseries, are never planted out in the wild. This will ensure genetic variability and alleviate unforeseen problems.
Early Hawaiian Use
Koa was the most valuable tree in Hawaii. 
In general, koa wood was also used in constructing houses (hale), spears, tools, paddles (hoe), kahili handles, calabashes (ʻumeke lāʻau), ceremonial poles (hulumanu), religious ceremonies, and short surfboards. [1,3,12,13,17,18]
While there were many uses for koa, it was never used for eating receptacles because the resin, which could not be removed, would leave a bad taste to foods. [2,18]
The prime importance of koa for early Hawaiians Early Hawaiians was making of canoes (waʻa), not only the single kinds with an outrigger, kaukahi, but even double kinds, kaulua, which consisted on two canoes lashed together with a yoke in a special way. 
Small narrow, long, light canoes, called kialoa or kioloa, were suitable for a single fisherman or for racing. Other smaller canoes, about 10 to 20 feet long, could accommodate six to eight men. These canoes were scarcely twelve inches at its widest and about two feet deep. 
Waʻa peleleu, or simply Peleleu, were long canoes or long voyages were usually 50 feet long, but some were 100 and even 150 feet long had a depth of 6 to 12, and even 15 feet, deep! Such canoes were 1 to 2 feet wide and carved from a single log. Some of these were made from the trunks of gian evergreens that had been carried by ocean currents and winds from the Pacific coasts of America. 
The bark was used as dye to stain kapa a red color. 
The leaves (phyllodes) were also used in lei making. 
Koa leaves were placed under a pile of lau hala mats if a person had been in a sick bed for a long time. Leaves were placed on top and spread evenly over the mat to make to person comfortable.The heat that came from the body and the leaves would make the person sweat. [7,9] Someone would wipe the sweat from the person as they fell asleep. This was almost always used for patients with a fever.  Young children under a year old who had become weak were given a mixture of koa leaf ash and other plants and applied inside the mouth. [7,9]
The bark was applied to pūhō (abscess, burst sore, ulcer), ʻalaʻala (scar, sore perhaps tuberculosis adentis), kaokao (syphilis), leprosy (maʻi lēpela), ʻeha māui (sore bruises), and haki (broken bones). 
Koa branches were made into booths for ritual purposes, in dedication of heiau. 
The Choosing & Making of Canoes
The process of selecting the correct tree for making a canoe (waʻa) was more than simply walking into a forest and picking out a tree to be used.
Before making a canoe, the Hawaiians employed a Kahuna, or priest, to offer prayers and sacrifices to Kū, the long-bearded god of canoes makers and of war, that the work should be successful. Then, the kahuna aided the men in selecting a suitable tree in the forest. This was a laborious work to fell a tree using a stone adze. The waʻa was then roughly hewn with the same tools.
If the native bird ʻelepaio (Chasiempis sp.), or the native crow, ʻalalā (Corvus tropicus),* settled on the log, this was considered an ill omen, and work on it was abandoned. Another tree was selected to take its place. If all went well, there was the chant to move the felled koa:
One would cry: "I kū mau mau!" (Stand together!). Then from all: "I kū wā!" (Shout!)
One: "I kū mau mau! I kū hulu hulu! I kū lanawao!" (Stand together! Haul with all your might! Under the mighty trees!)
All: "I kū wā!" (Shout!)
One: "I kū lanawao!" (Under the mighty trees!)
All: "I kū wā!" (Shout!)
"I kū wa huki!" (Shout! Pull!)
"I kū wa ko!" (Shout! Push!)
"I kū wa a mau!" (Shout! ...Snagged!)
"A mau ka ēulu!" (Snagged in the tree top!)
"E huki e!" (PULL!) "Kūlia!" (STRIVE!) 
Although the waʻa was made from koa, a number of other woods were used to construct and complete the project. Among them were ʻōhiʻa (Metrosideros spp.), ʻahakea (Bobea spp.), wiliwili (Erythrina sandwicensis), kamani (Calophyllum inophyllum), ʻulu (Artocarpus altilis), kukui (Aleurites moluccana), and hau (Hibiscus tiliaceus), to name a few, with the last three being Polynesian introduced plants. 
* ʻElepaio are only known to have existed on Kauaʻi, Oʻahu and Hawaiʻi Island; ʻAlalā is only known from Hawaiʻi Island. Both are still found today on these islands. While there is no fossil evidence of ʻelepaio found on other islands, there were two other Corvus species found on the islands of Oʻahu and Molokaʻi at the time of early Polynesian settlers.
Today, koa is propagated and planted in forest restoration projects and/or used as shade trees in home gardens. 
The wood is still very much prized in wood craft and is high in demand, being one of the most expensive woods in the world. [1,12,15]
Koa is also a tonewood and used in modern musical instruments such as ʻukulele, acoustic guitars such as used country music artist Taylor Swift, some electric guitars, and Weissenborn-style Hawaiian steel or lap guitars. [5,15]
Dyes, or tannins, are still made from koa bark. The dye colors will range from light to very dark (blackish) browns according to the mordant (dye setting metal substance) used on the fabric. [4,18]
 "Growing Koa" by Kim M. Wilkinson, pages 5, 7, 11-12, 35-36, 39, 55, 58, 59, 84.
 "Plants in Hawaiian Culture" by Beatrice H. Krauss, pages 22, 52, 65.
 "Arts and Crafts of Hawaii" by Te Rangi Hiroa (Sir Peter H. Buck), page 384.
 "Hawaii Dye Plants and Dye Recipes" by Val Frieling Krohn-Ching, pages 77, 136.
 http://en.wikipedia.org/wiki/Acacia_koa [Accessed 10/7/09]
 "Plants of the Canoe People" by W. Arthur Whistler, page 27.
 "Native Plants Used as Medicine in Hawaii" by Beatrice Krauss, page 20.
 "Nā Lei Makamae--The Treasured Lei" by Marie A. McDonald & Paul R. Weissich, page 42.
 "Hawaiian Herbs of Medicinal Value, by D.M. Kaʻaiakamanu & J.K. Akina, page 46.
 "Native Hawaiian Medicine--Volume III" by The Rev. Kaluna M. Kaʻaiakamanu, pages 62-63.
 "Hawaii Forest Disease and Pests" http://www.ctahr.hawaii.edu/forestry/disease/index.html [Accessed 2/4/11; updated on 4/28/10]
 "In Gardens of Hawaii" by Marie C. Neal, pages 410-411.
 "Lāʻau Hawaiʻi: Traditional Hawaiian Uses of Plants" by Isabella Aiona Abbott, pages 80, 83, 87-88, 110, 115, 129.
 "The Hawaiian Honeycreeper: Drapandidae" by H. Douglas Pratt, pages 129, 209, 210, & Plate 1.
 "Contemporary Woodworkers" by Tiffany DeEtte Shafto & Lynda McDaniel, pages 170, 172.
 "Traditional Trees of the Pacific Islands" by Craig R. Elevitch, pages 1, 4, 5, 6, 7.
 "How to Plant a Native Hawaiian Garden" by Kenneth M. Nagata, page "Koa."
 "Ethnobotany of Hawaii" by Beatrice H. Krauss, pages 127-130.
 "Extinct Birds" by Julian P. Hume & Michael Walters, pages 246-247.
 Ikuna Koa Outrigger Canoe Club http://www.ikunakoaoutriggercanoeclub.com [Accessed on 9/26/13]
 Hawaiian Dictionaries online http://wehewehe.org [Accessed on 9/27/13]
 "Pests and Diseases of Acacia Koa" by J. B. Friday in "Hawaii Landscape" Sept./Oct. 2013, page 24.
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