Coconut palm.

Coconut

Cocos nucifera

Origin:

The centre of diversity is commonly thought to be south east Asia and the Pacific islands, but there is good evidence that the real origin was at the confluence of South America and southern Africa when joined in Gondwana.  With its ability to float long distances in oceans it is thought to have been the first truly pan-tropical species.  Humans then dispersed it further to inland areas.  Cocos is a monotypic genus.

Climate:

They grow best within 23 degrees of the equator, where temperatures are 20-34°C, rainfall of 1300-2300mm pa is well-distributed and humidity is 70-80%.  Mature trees might survive frosts but inflorescences abort below 15°C.  Sunshine is also a prerequisite for good yields, with a minimum of 2000hr pa suggested. They may grow but not fruit properly in areas with insufficient warmth, such as Bermuda.

Plant Description:

It is a monocotyledonous palm that can grow to 20-30m high with a single terminal growing point and no axillary vegetative buds; stem branching is unusual and is caused by sub-lethal damage to the growth apex.  The fibrous root system is adventitious with a mature plant having thousands, some of which can spread outwards for 20m and downwards for 2m; 70% are surface (10-50cm) and found within 1m of the stem. There is no tap root nor root hairs. Mature plants have 30-40 long-lived leaves (fronds), 3-6m long, with each having 200-250 leaflets, 60-70cm long. There are 2 basic types: 'Tall' and 'Dwarf'.

Relatives:

Arecaceae Family, which also includes betel nut, sugar palm, peach palm, palmyra palm, oil palm and the date palm.  This large family consists of approx. 200 genera and 2500 species; worldwide it is the 3rd-most economically important family after the grasses and legumes.

Soils:

Best yields are obtained on well-drained fertile soils, but as everyone knows, it can also grow in very infertile and challenging environments such as open beach sands. It is highly tolerant of salinity. Soil pH is not critical, pH 5-8 is tolerated.

Propagation:

Only propagated by seed from good performing varieties; grafting with palms is not possible.  The nuts should be collected when skin colour is just turning brown and you should be able to hear a sloshing noise when shaken.  With the husk left on, plant shallowly (only half-covered with soil or sand) with the flat side down. Sometimes the germ end of the nut is trimmed to facilitate imbibition.  Keep moist and warm.  Some months may elapse before a shoot emerging through one of the 3 eyes becomes visible.  After transplanting, the plant should be well-watered to stimulate root development.  The endosperm contains enough nutrients for growth over the first year.

Cultivars:

There are two basic types of coconut, namely the more common tall types (typica) and the dwarf (nana), with an overwhelming and confusing profusion of local common names.  Some key features of each type include: for tall - juvenility 6-8yrs, pollination by outcrossing, fruit large and harvesting more difficult, and for dwarf - juvenility 1.5-3yrs, self-pollination, fruit smaller and alternate bearing.    Dwarf types may fruit almost at ground level. Some varieties you may come across are:

  1. Jamaican Tall
  2. Malay Dwarf
  3. The Gai coconut, called the 'sweet' coconut, which grows on Torres Strait Island, has an edible husk.
  4. Samoan Dwarf, which produces a giant coconut.
  5. Makapuno, the cavity of the fruit is filled with a uniform soft, sweet flesh, rather than the usual liquid centre surrounded by solid flesh. It is much in demand for desserts and sweets.

There are many sub-varieties in all of these.

Flowering and Pollination:

Coconut is monoecious with staminate and pistillate flowers occurring in axillary inflorescences (spadix) enclosed in a spathe.  As each spadix matures it emerges from the spathe on a branched rachis, 1-1.5m long.  Each rachilla has one or more basal pistillate flowers and many more distal staminate flowers.  Pistillate flowers are globose, 2.5cm diameter, with a short style, 3 stigmas and 3 ovules of which only one is usually fertile.  Staminate flowers are small, 3mm,  with 6 stamens.  Staminate flower anthesis occurs in a staggered fashion over some weeks but each flower is only open for a day before abscission.  Stigmas are receptive for 2-3 days but in a given spadix this typically happens after staminate anthesis has finished, favouring cross-pollination.  Warmer temperatures may improve the overlap whereas in dwarf types there is usually better synchronisation.  Pollination is principally by insects but wind may also contribute. There tends to be a great excess of male flowers. The dwarf type is more commonly self-fertile and precocious. The 'Tall' variety requires cross pollination. Extensive inflorescence abortion occurs below 10-15°C.

Cultivation:

Coconut should be planted in a location with full sun and irrigation should be provided in any dry periods.  The extended maturation period of coconut fruit is just one of the many difficulties faced in detailed fertilization studies.  Nevertheless, it is known that seedlings should be given small amounts of a complete fertilizer with trace elements, and this should then increase with plant growth.  Adequate NPK has been demonstrated to significantly influence yield.

Wind Tolerance:

Excellent, as we all see from documentaries of tropical island cyclones.

Pruning:

They are self-pruning.

The Fruit:

It is a fibrous drupe, ovoid, 20-30cm long and weighing 1-2 kg.  There is a thin epidermis covering a thick fibrous mesocarp (husk) and a hard thick brown endocarp (shell) enclosing the white endosperm (kermel) with a large central fluid-filled cavity.  The small embryo lies in the flesh under the 'soft eye'.  The common name of 'nut', even though almost universally used, is a misnomer.  The kernel is about 28% of the whole fruit and contains 27% fat, 14% carbohydrate, 4% fibre and a good level of Fe.   Even though almost all the fat is of the saturated type, it is less damaging than others because a good proportion is of the short chain types which aren’t metabolised like traditional saturated fats.

Fruit Production and Harvesting:

It may take more than 3 years from flower initiation to fruit maturity; hence growing conditions in this period may determine yield over the next 30 months.  If less than  adequate, there may be considerable fruit drop due, for example, to defective pollination, drought, pests and diseases or simply poor palm condition.  A well-managed mature tall type can produce up to 100 coconuts per year, throughout the year.  Harvesting the fruits of dwarf trees is not difficult, but for tall ones you might have to wait till they fall unless you’re a brave climber.  Mature coconuts in husk can be kept at ambient temperature for 3-5 months before the coconut water has evaporated and the shell cracks.

Fruit Uses:

Many uses for the fruit. The water inside is used as a drink, the flesh is grated and consumed in many ways: in main dishes and processed products such as breads, cakes, pies and ice cream, or pressed to extract oil, coconut cream and coconut milk. Even sprouted coconuts can be eaten: the centre fills out and has a soft puffy texture that is tasty and very sweet. It tastes very different from unsprouted coconut meat. All parts of the tree provide useful products.

Pests and Diseases:

Plant hoppers and scale may cause problems.  Several diseases may also occur, including bud rot (Phytophthora spp), basal stem rot, grey leaf blight and stem bleeding.  Lethal yellowing disease is caused by a phytoplasma spread by leaf hoppers and can be a major quarantine concern. Weed control is essential during early plant establishment.

Comments:

If you’re a backyarder you should go for a dwarf type, whereas those with acreage might prefer the more regular bearing habit and bigger yields of the tall types.

There is some evidence that coconut trees benefit from an occasional watering with sea water.