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The Coconut Palm: A Hawaiian Icon

5 Apr

My introduction to the Islands, long before I came to my Hawai’i nei, was a peeled coconut I bought in a local grocery store in California. The first thing I noticed was the three conspicuous round depressions at one end of the nut. My Dad said they were the coconut’s eyes. Fifty years later I read that these “eyes” were actually the germination pores out of which a root-sprout eventually appears. About the same time I discovered this old Hawaiian belief: Coconuts have eyes so they can see where they fall and so never fall on anyone. I like that explanation better…

Coconut endocarp with germination pores

Coconut endocarp (shell) displaying the three characteristic germination pores or “eyes.”

The Coconut Palm (Cocos nucifera) is a member of the family Arecaceae (palm family). The genus name “Cocos” may have come from a Portuguese word meaning “monkey”, perhaps because its nut, bearing three germinating pores, resembles a monkey’s face. Its species name is derived from the Latin phrase meaning “nut-bearing” (that is, fero = “I bear” and nux-nucis = “nut”). In English, it is referred to as “coconut”, “cocoanut”, and “coconut palm”, all of which stem from the name of the fruit, not so much the tree itself. In Polynesian and Melanesian languages it is called “niu”, which is derived from the Malay words “nyiur” or “nyior”. This derivation may indicate that the species originated in the Malay-Indonesian region.

Distribution

The Coconut Palm is found in all tropical and subtropical regions 25 degrees north and south of the equator. Its distribution includes most of the world’s tropical islands and coastal regions. Rarely its range extends outside the tropics, where it will flower, but fruits fail to develop normally. Cocos nucifera is believed to have originated in the coastal areas of Southeast Asia (Malaysia, Indonesia, Philippines). In prehistoric times a wild precursor may have been carried eastward on ocean currents to the tropical Pacific islands (Melanesia, Polynesia, and Micronesia) where they established themselves on abundant sandy and coralline coasts. More than four thousand five hundred years ago, Polynesians migrating into the tropical regions of the Pacific Basin probably carried select aboriginal coconut species (“niu vai”) with them on their ocean-going canoes. Some researchers believe that the tree originated along the northwestern coast of South America. There is fossil evidence (more than 15 million years old) of small coconut-like plants in New Zealand and the Indian Subcontinent. Regardless of its origin, the Coconut Palm has spread inland (with the help of migrating humans) and flourishes in a wide variety of soil types and at altitudes in excess of 600 meters (1,970 feet) above sea level. Although it is considered to be a non-native species in the Hawaiian Islands, there is no danger of the Coconut Palm becoming an invasive nuisance species because the large size and low numbers of fruits produced by a single tree restrict its ability to spread uncontrollably.

Coconut palms on a Kihei beach. (Click on image for larger version.)

Mature coconut palms, Kalepolepo Beach, Maui. (Click on image for a larger version.)

Description

Of the two major classes of coconut palms, tall (average height at maturity is 18 m) and dwarf (average height 6 m), the tall variety is most common; and so, for the purposes of this blog, all my descriptions refer to that variety.

Coconut palms @ Kaenae Village church

A nice stand of mature trees, Keanae Village, Maui. (Click on image for a larger version.)

Growth Rate – A Coconut Palm will grow continuously throughout the year under ideal environmental conditions (uniform soil moisture, high humidity and air temperature). The tall variety of Coconut Palm is slow to mature, setting flowers six to ten years after planting. During the first 40 years of a tree’s life it averages 30 to 50 cm of growth annually. After about four years, the majority of growth occurs in the trunk. Fruit production increases after the sixth year at the expense of vegetative growth. Thereafter, growth is fairly constant as fruit yields are sustained for the next 40 years. The average lifespan of the tree is 60 to 70 years, but some trees live more than 100 years.

Cocos nucifera-immature coconuts

Immature coconuts; note the green exocarp (skin).  (Click on image for a larger version.)

Tree – The bark of the solitary trunk is smooth, colored ash-gray to almost white, and marked by numerous ring-shaped scars left by the basal attachments of leaves that have fallen as the trunk grows in height. The strong yet very flexible trunk enables the tree to bend freely in heavy wind. There are numerous stories of people stranded during tropical storms lashing themselves to the trunks of mature coconut palms to prevent being washed out to sea. It is not unusual to see trunks of mature trees that are leaning over at a precarious angle or that have been noticeably contorted: this is usually due to the tree reaching upward for greater exposure to sunlight. More extremely misshapen trunks are caused by nutritional deficiencies.

Cocos nucifera nearly ripe nuts

Ripening coconuts; note yellowish-brown exocarp. (Click on image for larger version.)

Leaves — Until about the end of the first year of growth, the leaves remain entire (that is, not divided into leaflets as in a mature tree). Thereafter, the leaves become progressively more pinnate (shaped like a bird’s feather). The full crown of the mature tree carries numerous (usually 20 to 30) leaves (referred to as “fronds”) that can be as much as 20 feet long and bear 200 to 250 dark-green, slightly recurved leaflets about one meter long. The petiole (or “stem”) of the frond takes up about 25 percent of the total length of the frond. The large base of the petiole provides a strong attachment for the frond to the trunk. Leaves remain attached to the tree’s crown for about 2.5 years after unfolding, whereupon they “senesce” (drop off), leaving the distinctive ring-like scar on the trunk.

Root System – Unlike most trees, a Coconut Palm has no tap root or root hairs. Instead the root system consists of  2,000 to 4,000 adventitious roots about one centimeter in diameter. The depth to which the roots extend depends on the soil type and depth to the local water table. Individual roots can grow to depths of five meters, the majority of the tree’s root system is concentrated in the upper 1.5 meters of the soil. Lateral growth averages six meters, but under ideal conditions will extend as far as 30 m outward from the base of the trunk.

Cocos nucifera-flowers

The male and female flowers of a mature tree.

Flowers – The Coconut Palm produces flowers 12 to 15 times a year. This species is monoecious: that is, it includes male and female flowers on the same inflorescence (a flower spike or “spadix”) that develops within a woody sheath (spathe). When flowering occurs, the spathe splits lengthwise, exposing the spadix. Each orange to straw-colored spadix is 1 to 1.5 m (3.3 to 5 ft) long with 40 to 60 branches (or spikelets) bearing the flowers. Each spikelet may carry as many as three female flowers (buttons) at its base and several hundred male flowers above. As a result, a spadix may carry several thousand male flowers but only 40 to 60 buttons. Coconut Palms are cross-pollinated, either by anemophily (pollen is carried on the wind) or entomophily (pollen is distributed by insects). However, pollination can occur between flowers of successive spadices on the same tree. A tree’s first flowering may occur at four to five years of age. When the tree reaches maturity, a spadix (flower spike) is produced on every leaf. Twelve to fifteen spadices (per leaf) are produced annually at regular intervals. Drought conditions can delay emergence of the spadix or cause it to abort. The number of female flowers per spadix varies, governed by environmental conditions.

Cocos nucifera-exocarp

A recently fallen coconut; note the greyish-white color of the exocarp. (Click on image for a larger version.)

Fruit (the “coconut”) – Each coconut fruit (technically not a true nut, it is known as a “fibrous drupe”) is about the size of a bowling ball and weighs more than two kilograms. Because it is relatively light and very buoyant, a fruit that is dropped in water or carried away on an incoming tide can be borne by ocean currents for a great distance and still be viable enough to germinate. Fruits that have remained in seawater for as much as 120 days are still able to germinate and take root successfully. A mature tree produces 50 to 80 fruits throughout the year. Roughly 40 percent of set fruit are carried to full term within three months of pollination. Although it takes 15 months from flowering for the fruit to mature, the drupe is usable (the water in the endocarp is fit to drink) at about five months.

Cocos nucifera-fruit cross-section

Immature coconut sliced open to show mesocarp (“coir”) and endocarp (“shell”). (Click on image for a larger version.)

Hawaiian names for the various stages of coconut fruit development:

  • ‘o ‘io – Unripened fruit contains jelly-like translucent flesh you can eat with a spoon.
  • hao hao – Almost half matured with shell still white and flesh is soft and white.
  • ho ‘ilikole – Half-ripe, meat eaten raw with red salt and poi.
  • niu o‘o – Fruit is mature but the husk has not dried.
  • niu malo‘o – Fruit is mature, the husk is dry, water still present; best stage for planting; used to make coconut cream, which when mixed with kalo/taro makes a dish called kulolo; with `uala/sweet potato it is called poipalau; and paipaie’e with ripe `ulu/breadfruit. The mature meat of coconut is also grated, squeezed or scraped to be cooked in main dishes with fish, chicken or greens.
  • niu ka‘a – Old fruit with no water and flesh separated from shell; coconut oil is extracted at this stage.
endocarp & endosperm-flesh

Endocarp (shell) cracked open to show solid portion (“meat”) of the endosperm. (Click on image to see a larger version.)

Parts of the Fruit

The exocarp is the thin outermost layer (or skin) of the fruit. The mesocarp is a thick husk composed of coarse brown fibers (coir). The endocarp is the hard, but relatively thin woody inner layer of a fruit that contains the endosperm. The endosperm is partly liquid (“coconut water”) and partly solid (fibrous white coconut “flesh” or “meat”, which adheres to the inner wall of the endocarp). The liquid portion of the endosperm is rich in minerals, vitamins, Lauric (fatty acid-based) oils, and carbohydrates. The minute embryo (or seed) is embedded in the solid fleshy portion of the endosperm just inside one of the three germination pores (called “eyes”) through which the radicle (the embryonic root of the seedling) emerges when the embryo germinates.

Cocos nucifera-mesocarp

A fallen coconut displaying the fibrous coir (mesocarp). (Click on the image to see a larger version.)

Coconut Water – This is the clear liquid portion of the endosperm. When the coconut is about six to seven months old, the water is ready to drink; the coconut is full-sized, but is still green with no trace of yellow on the exocarp. This is the point in the growth cycle when the jelly-like flesh of the endosperm begins to solidify. The coconut should be picked by hand, not fallen from the tree. At this point there is about one liter of liquid in the coconut, but you can’t hear it inside the fruit when shaken. The water is at its sweetest and it is lowest in acidity, and can only be stored for about two days. The characteristics of the water change as the fruit matures: an immature coconut 3 – 5 months old (before the endosperm begins to form) has tasteless water that is somewhat astringent; the water of a mature coconut has a slightly salty taste and is more acidic.

Coconut Milk –  This should not be confused with coconut water. When a mature coconut drops off the tree, it still contains some of the liquid endosperm. This can be combined with grated coconut meat to make coconut milk. It has a fat content of approximately 17 percent. The milk is used to produce virgin coconut oil by means of fractionation (a closely controlled heating process); when the process is completed, the oil fraction is drawn off.

coconut germinating

A fallen coconut germinated in volcanic soil.

Preferred Environment

Soils – The Coconut Palm is capable of adapting to a remarkable variety of soil types, from very coarse or gravelly soil to clay, as long as they possess good drainage and aeration. It does not tolerate oversaturated soil within about one meter of the surface, and will not survive more than two weeks of surface water-logging. Although coarse sand is its preferred soil type, it will grow readily in loamy soils as well as clay soils that are well drained. It is very tolerant of soils with high salinity and is not bothered by salt spray. It tolerates alkaline soils with a pH of 8 and acid soils with a pH of more than 4.5. Its preferred pH range is 5.5 – 7.

Climate – Obviously a plant of the tropics, the Coconut Palm prefers a year-round warm and humid climate characteristic of the coasts of large landmasses and islands where the sea exerts a moderating influence on temperature and humidity. A mean annual temperature of 27°C (81°F), evenly distributed annual rainfall of 1500 to 2500 mm (60 -100 in), and high relative humidity (more than 60 percent) are the ideal climatic conditions for the healthy growth and propagation of the palm. A permanent water table within easy reach of its roots can make up for inadequate rainfall, while annual rainfall in excess of 2500 mm (100 in) render the tree vulnerable to diseases of the leaves and fruit. The Coconut Palm does not tolerate low temperatures and will not survive in sustained temperatures much below 2°C (36°F). However, some seasonal variation is tolerated: it will survive brief periods of freezing temperatures (0 to -4 °C), but severe frost is usually fatal. It also does poorly under sustained drought conditions. Symptoms of drought-induced stress include desiccated older fronds, new fronds that fail to open normally, and the premature shedding of immature fruits. Though it prefers to grow in full sunlight, the Coconut Palm will tolerate some shading by other trees, but it is slow to mature and produces fewer fruits under heavily-shaded conditions. If the tree’s root system is well anchored, it is able to withstand hurricane-force winds with ease. The innate flexibility of the tree’s trunk and fronds reduces its cross-sectional area and lowers the drag forces to which it is subjected during high-wind conditions.

Coconut Palm Products and Uses

In those parts of the world where the Coconut Palm grows naturally and is widely cultivated, indigenous people have learned to make use of nearly every part of the tree. For thousands of years, the “people of the coconut palm” have learned to use the trunk wood and roots, foliage, flowers, and fruit of the tree to fashion tools, weapons, hardware, building and clothing materials, and decorative and religious works of art. From the meat, oil, milk, and water of the coconut’s fruit they have produced an astonishing menu of appetizing and nutritious food items, as well a voluminous pharmacopeia of traditional medicines and treatments.

A note about the uses of Cocos nucifera in the Hawaiian Islands – The Hawaiian Islands are located on the northernmost edge of what may be called the “Coconut Belt”. In the islands and continental regions that are closest to the equator, the Coconut Palm is more numerous and productive of its fruits, and so it was and is more widely used there than in Hawai`i. Here there have always been other plants, native and introduced, that provide as well for people’s needs, and so the Coconut Palm plays a somewhat subordinate role in Hawaiian culture. However, Niu was considered to be such a valuable plant that it was included as cargo on the crowded sailing canoes of the original Polynesian voyagers who colonized Hawai`i Nei. For this reason, and because Cocos nucifera has become so emblematic of the Hawaiian Islands and is such a visible presence here, the Coconut Palm enjoys a popularity (and even a kind of reverence) here in the Islands that is out of proportion to its actual role in Hawaiian history and culture.

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