Species of flowering tree endemic to the Hawaiian Islands
Acacia koa
, commonly known as
koa
,
[3]
is a species of
flowering
tree
in the
family
Fabaceae
. It is
endemic
to the
Hawaiian Islands
,
[2]
where it is the second most common tree.
[4]
The highest populations are on
Hawai?i
,
Maui
and
O?ahu
.
Name
[
edit
]
The name
koa
in the
Hawaiian language
ultimately comes from
Proto-Austronesian
*
teRas
meaning "core" or "
ironwood
"; many names referring to certain ironwood or heartwood species in Southeast Asia and Oceania such as
Vitex parviflora
(
tugas
in
Cebuano
),
Eusideroxylon zwageri
(
togas
in
Tombonuwo
), and
Intsia bijuga
(
dort
in
Palauan
) descend from this root.
[5]
Koa
also means brave, bold, fearless, or warrior.
[3]
Description
[
edit
]
Upper branches of a koa tree, showing the bark, sickle-shaped
phyllodes
, greenish rounded flower heads, and seedpods
Koa is a large
tree
, typically attaining a height of 15?25 m (49?82 ft) and a spread of 6?12 m (20?39 ft).
[6]
In deep
volcanic ash
, a koa tree can reach a height of 30 m (98 ft), a circumference of 6 m (20 ft), and a spread of 38 m (125 ft).
[7]
It is one of the fastest-growing Hawaiian trees, capable of reaching 6?9 m (20?30 ft) in five years on a good site.
[8]
Leaves
[
edit
]
Initially,
bipinnately compound leaves
with 12?24 pairs of
leaflets
grow on the koa plant, much like other members of the
pea family
. At about 6?9 months of age, however, thick sickle-shaped "leaves" that are not compound begin to grow. These are
phyllodes
, blades that develop as an expansion of the leaf
petiole
. The vertically flattened orientation of the phyllodes allows sunlight to pass to lower levels of the tree. True leaves are entirely replaced by 7?25 cm (2.8?9.8 in) long, 0.5?2.5 cm (0.20?0.98 in) wide phyllodes on an adult tree.
[6]
Flowers
[
edit
]
Flowers
of the koa tree are pale-yellow
spherical
racemes
with a diameter of 8?10 mm (0.31?0.39 in).
[9]
Flowering may be seasonal or year round depending on the location.
[6]
Fruit
[
edit
]
Fruit
production start occurring when a koa tree is between 5 and 30 years old. The fruit are
legumes
, also called pods, with a length of 7.5?15 cm (3.0?5.9 in) and a width of 1.5?2.5 cm (0.59?0.98 in). Each pod contains an average of 12
seeds
. The 6?12 mm (0.24?0.47 in) long, 4?7 mm (0.16?0.28 in) wide seeds are flattened
ellipsoids
and range from dark brown to black in color. The pods are mature and ready for propagation after turning from green to brown or black. Seeds are covered with a hard
seed coat
, and this allows them to remain
dormant
for up to 25 years.
Scarification
is needed before
A. koa
seeds will
germinate
.
[9]
Habitat
[
edit
]
Koa is
endemic
to the
islands
of
Hawai?i
,
Moloka?i
,
Maui
,
L?na?i
,
O?ahu
, and
Kaua?i
, where it grows at elevations of 100?2,300 m (330?7,550 ft). It requires 850?5,000 mm (33?197 in) of annual rainfall.
Acidic
to neutral
soils
(
pH
of 4?7.4)
[6]
that are either an
Inceptisol
derived from
volcanic ash
or a well-drained
histosol
are preferred.
[10]
Its ability to
fix nitrogen
allows it to grow in very young volcanic soils.
[4]
Koa and ??hi?a lehua (
Metrosideros polymorpha
) dominate the
canopy
of Hawaiian
mixed mesic forests
.
[11]
It is also common in
wet forests
.
[12]
Uses
[
edit
]
The American
Pop
singer
Taylor Swift
with a
Taylor
acoustic guitar
made of
Acacia koa
wood
The koa's trunk was used by
ancient
Hawaiians
to build
wa?a
(
dugout
outrigger canoes
)
[13]
and
papa he?e nalu
(
surfboards
). Only
paipo
(
bodyboards
),
kiko?o
, and
alaia
surfboards were made from koa, however;
olo
, the longest surfboards, were made from the lighter and more
buoyant
wiliwili
(
Erythrina sandwicensis
).
[14]
The reddish wood is very similar in strength and weight to that of Black Walnut (
Juglans nigra
), with a specific gravity of 0.55,
[9]
and is now sought for use in
wood carving
and
furniture
.
[6]
Koa is also a
tonewood
,
[15]
often used in the construction of
ukuleles
,
[16]
acoustic guitars
,
[17]
and
Weissenborn
-style Hawaiian
steel guitars
.
[18]
B.C. Rich
used koa on some of their
electric guitars
as well,
[19]
and still uses a koa-
veneered
topwood
on certain models.
[20]
Fender made limited edition koa wood models of the
Telecaster
and the
Stratocaster
in 2006.
Trey Anastasio
, guitarist for the band
Phish
, primarily uses a koa hollowbody
Languedoc
guitar. Commercial
silviculture
of koa takes 20 to 25 years before a tree is of useful size.
[21]
A thinly sliced section of wide Hawaiian Koa lumber
Taylor, Collings and Martin are few among the many other brands that use that tonewood for manufacturing acoustic guitars.
[22]
Relation to other species
[
edit
]
Koai?a seedpod, showing the end-to-end arrangement of seeds
Among other
Pacific Islands
of
volcanic
(non-
continental
) origin, only
Vanuatu
has native
Acacia
species.
A. heterophylla
, from distant
Reunion
, is very similar and has been suggested to be the closest relative of koa.
[23]
Genetic sequence analysis results announced in 2014 confirmed this close relationship; the estimated time of divergence is about 1.4 million years ago.
[24]
[25]
A. heterophylla
sequences nest within those of the more diverse
A. koa
, making the latter
paraphyletic
.
[25]
Both species are thought to be descended from an ancestral species in Australia, presumably their
sister species
,
Acacia melanoxylon
. Dispersals most likely occurred via seed-carrying by birds such as
petrels
.
[25]
Both species have very similar
ecological niches
, which differ from that of
A. melanoxylon
.
[25]
A closely related species, koai?a or koai?e (
A. koaia
), is found in dry areas. It is most easily distinguished by having smaller seeds that are arranged end-to-end in the pod, rather than side by side. The
phyllodes
are also usually straighter, though this character is variable in both species. The wood is denser, harder, and more finely
grained
than koa wood.
[6]
Koai?a has been much more heavily impacted by
cattle
and is now rare, but can be seen on
ranch
land in
North Kohala
.
[
citation needed
]
Conservation
[
edit
]
The koa population has suffered from grazing and
logging
. Many
wet forest
areas, where the largest koa grow, have been logged out, and it now comes largely from dead or dying trees or farms on private lands. Although formerly used for
outrigger canoes
, there are few koa remaining which are both large and straight enough to do so today.
[6]
In areas where
cattle
are present, koa regeneration is almost completely suppressed. However, if the cattle are removed, koa are among the few native Hawaiian plants able to
germinate
in grassland, and can be instrumental in restoring native
forest
. It is often possible to begin
reforestation
in a
pasture
by disk
harrowing
the soil, as this
scarifies
seeds in the soil and encourages large numbers of koa to germinate.
[10]
Experiments at the
Hakalau Forest National Wildlife Refuge
have shown that ??hi?a lehua (
Metrosideros polymorpha
) survives best in pasture when planted under koa. This is because koa trees reduce
radiative cooling
, preventing
frost
damage to ??hi?a lehua seedlings.
[26]
Ecology
[
edit
]
Koa is the preferred
host
plant for the
caterpillars
of the green Hawaiian blue (
Udara blackburni
), which eat the flowers and fruits.
[27]
Adults drink
nectar
from the flowers. Koa
sap
is eaten by the adult Kamehameha butterfly (
Vanessa tameamea
).
[28]
The koa bug (
Coleotichus blackburniae
) uses its rostrum to suck the contents out of koa seeds.
[29]
Koa is vulnerable to infection by
koa wilt
.
Gallery
[
edit
]
References
[
edit
]
- ^
Contu, S. 2012.
Acacia koa
. The IUCN Red List of Threatened Species 2012: e.T19891713A19999145.
https://dx.doi.org/10.2305/IUCN.UK.2012.RLTS.T19891713A19999145.en
. Downloaded 8 May 2017.
- ^
a
b
"
Acacia koa
"
.
Germplasm Resources Information Network
.
Agricultural Research Service
,
United States Department of Agriculture
. Retrieved
2010-05-03
.
- ^
a
b
Kepler, Angela Kay (1998).
Hawaiian Heritage Plants
. University of Hawaii Press. p. 106.
ISBN
978-0-8248-1994-1
.
- ^
a
b
Idol, Travis (2008-04-16).
"Environmental Controls Over Acacia koa Productivity"
.
Travis Idol's Research Page
.
University of Hawai?i at M?noa
. Retrieved
2009-01-31
.
- ^
Blust, Robert
; Trussel, Stephen (2010).
"*
teRas
: heartwood of a tree, hard, durable core of wood; ironwood tree"
.
Austronesian Comparative Dictionary
. Max Planck Institute for Evolutionary Anthropology
. Retrieved
27 December
2022
.
- ^
a
b
c
d
e
f
g
Elevitch, Craig R.; Kim M. Wilkinson; J. B. Friday; C. Baron Porter (April 2006).
"Acacia koa (koa) and Acacia koaia (koai?a)"
(PDF)
. The Traditional Tree Initiative.
- ^
Welsbacher, Anne (2003).
Life in a Rain Forest
. Twenty-First Century Books. p. 30.
ISBN
978-0-8225-4685-6
.
- ^
Wilkinson, Kim M.; Craig R. Elevitch (2003).
Growing Koa: A Hawaiian Legacy Tree
.
H?lualoa, Hawai'i
: Permanent Agriculture Resources. p. 13.
ISBN
978-0-9702544-2-9
.
- ^
a
b
c
Allen, James A. (2003-01-01).
"Acacia koa A. Gray"
(
PDF
)
.
Tropical Tree Seed Manual
. Reforestation, Nurseries & Genetics Resources
. Retrieved
2009-02-23
.
- ^
a
b
Whitesell, Craig D (1990).
"
Acacia koa
"
. In Burns, Russell M.; Honkala, Barbara H. (eds.).
Hardwoods
.
Silvics of North America
. Vol. 2.
Washington, D.C.
:
United States Forest Service
(USFS),
United States Department of Agriculture
(USDA).
Archived
from the original on 20 January 2009
. Retrieved
2009-02-17
– via Southern Research Station.
- ^
Ziegler, Alan C. (2002).
Hawaiian Natural History, Ecology, and Evolution
. University of Hawaii Press. pp. 175?176.
ISBN
978-0-8248-2190-6
.
- ^
Sohmer, S. H.; R. Gustafson (1987).
Plants and Flowers of Hawai?i
. University of Hawaii Press. pp. 45?52.
ISBN
978-0-8248-1096-2
.
- ^
Bryan, William Alanson (1915).
Natural History of Hawaii, Being an Account of the Hawaiian People, the Geology and Geography of the Islands, and the Native and Introduced Plants and Animals of the Group
. Hawaiian Gazette Co, Ltd. p.
339
.
ISBN
978-1-4446-7820-8
.
- ^
Marcus, Ben; Juliana Morais; Jeff Divine; Gary Linden (2007).
The Surfboard: Art, Style, Stoke
. MBI Publishing Company. pp. 17?19.
ISBN
978-0-7603-2753-1
.
- ^
Beberman, Norman L.
"Koa: Beautiful Looking, Beautiful Sounding Tonewood"
. GuitarNation.com.
Archived
from the original on 7 February 2009
. Retrieved
2009-02-23
.
- ^
Gernot Rodder (2002).
Total Ukulele: D-Tuning Method for Beginners
. Mel Bay Publications. p. 93.
ISBN
978-3-8024-0446-7
.
- ^
Gerken, Teja (2000).
Acoustic Guitar Owner's Manual: The Complete Guide
. String Letter Publishing. p. 10.
ISBN
978-1-890490-21-8
.
- ^
Sheperd, John (2003).
"Guitars"
.
Continuum Encyclopedia of Popular Music of the World
. Vol. II: Performance and Production. Continuum International Publishing Group. p. 283.
ISBN
978-0-8264-6322-7
.
- ^
Achard, Ken (1989).
The History and Development of the American Guitar
. Bold Strummer Ltd. p. 163.
ISBN
978-0-933224-18-6
.
- ^
Kirkland, Eric (December 2006). "Rich and Famous".
Guitar World
: 154.
- ^
"Silviculture: Diversification of Rural Economy"
. Leeward Haleakal? Watershed Restoration Partnership
. Retrieved
2009-02-01
.
- ^
"Is Koa Wood The Ultimate Choice For Guitar Enthusiasts?"
. Best Guitars Now
. Retrieved
2023-11-24
.
- ^
Whitesell, Craig D (1964).
"Silvical Characteristics of Koa (
Acacia koa
Gray)"
(PDF)
.
United States Forestry Service
.
- ^
Marris, E. (2014-06-19).
"Tree hitched a ride to island"
.
Nature
.
510
(7505): 320?321.
Bibcode
:
2014Natur.510..320M
.
doi
:
10.1038/510320a
.
PMID
24943937
.
- ^
a
b
c
d
Le Roux, J. J.; Strasberg, D.; Rouget, M.; Morden, C. W.; Koordom, M.; Richardson, D. M. (2014-06-18).
"Relatedness defies biogeography: The tale of two island endemics (Acacia heterophyllaandA. Koa)"
.
New Phytologist
.
204
(1): 230?242.
doi
:
10.1111/nph.12900
.
PMID
24942529
.
- ^
Friday, J. B.; Darrell A. Herbert (April 2006).
"Metrosideros polymorpha ('?hi'a lehua)"
(PDF)
. The Traditional Tree Initiative: 21.
- ^
Scott, James A. (1992).
The Butterflies of North America: A Natural History and Field Guide
. Stanford University Press. p. 399.
ISBN
978-0-8047-2013-7
.
- ^
Scott, Susan (1991).
Plants and Animals of Hawaii
. Bess Press. p.
78
.
ISBN
978-0-935848-93-9
.
- ^
"Koa Bug Investigation"
(PDF)
.
Uhh.hawaii.edu
. Retrieved
15 March
2022
.
External links
[
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]