Nypa fruticans (nipa palm)

The spread of nipa in the coastal zones of Nigeria threatens the mangrove vegetation of the zone by outcompeting and displacing the native mangrove species, thereby lowering biodiversity as well as affecting people's livelihoods through reduced fish catch and reduced collection of shellfish.

With its prostrate, dichotomously branched stem and its erect inflorescence bearing a terminal head of female flowers and lateral spikes of male flowers, Nypa fructicans, the nipa palm, occupies a unique position in the Palmae. It is considered an advanced palm species, with a very long history; possible relations with the genera Pandanus and Sararanga (both from the Pandanaceae) have been suggested. In South-East Asia, the size of the nipa palm varies: in the Philippines plants are smaller than in Papua New Guinea and Malaysia. In Malaysia, two forms of nipa palms are distinguished, 'nipah gala' and 'nipah padi', differing in the tilt of the leaflets. No cultivars have been developed.

A large, creeping, unarmed, pleonanthic, monoecious palm. Stem prostrate or subterranean (rhizome), up to 45 cm in diameter, branching dichotomously at regular intervals, with curved leaf scars above, and roots along the underside. Erect shoots arise from each rhizome branch. Each shoot has a tuft of 3-5 leaves at any time, the leaves erect, 4.5-14.2 m long, simply pinnate; petiole very stout, up to 1.5 m long, channeled adaxially, terete distally, dilated towards the base into a short sheath; leaflets up to 163 per leaf, linear, single-fold, 1.2-1.5 m x 6.5-8.6 cm, coriaceous, midrib bearing appressed brown scales on lower surface. Inflorescence solitary, interfoliar, erect, branched, multibracteate, protogynous, up to 2.1 m long with a stout, terete, up to 2.4 m long peduncle; rachis usually shorter than the peduncle, terete, terminating in a globose head of female flowers surrounded by numerous, short, catkin-like rachillas (spikes) terminating the lateral branches and bearing densely crowded, spirally arranged, solitary male flowers, most branches subtended by large, tubular, rubbery bracts protecting flowers and fruits; male spikes usually in pairs, cylindrical, often slightly curved, up to about 5 cm long; flowers extremely dimorphic but six perianth parts similar for both sexes; male flowers with three stamens, filaments united into a column, without pistillodes; female flowers without staminodes; carpels (pistils) 3, distinct, much longer than perianth, irregularly polyhedric, curved and angled, with a funnel-shaped stylar opening. Fruiting head subglobose, up to 40 cm in diameter, fertile and partially developed fruits intermixed; fruit a drupe, developing from carpel, compressed and irregularly angled, pyramidal, 10-15 x 6-8 cm, brown to blackish, exocarp smooth, mesocarp fibrous, endocarp thick and composed of interwoven fibrous strands. Seed broadly ovoid, grooved adaxially, hilum basal, endosperm homogeneous. Germination is on the infructescence (viviparous), with the plumule exserted and pushing the fruit away; eophyll bifid or with several leaflets.

Nipa palm is one of the oldest angiosperm plants and probably the oldest palm species. Eocene and Miocene fossils in Europe, North America and the Middle East and the Paleocene strata in Brazil suggest that nipa palm had a pantropical distribution 13-63 million years ago. Today it is mainly found in the equatorial zone, 10°N-10°S, stretching from Sri Lanka through South-East Asia to North Australia. The largest natural nipa stands are found in Indonesia (700,000 ha), Papua New Guinea (500,000 ha) and the Philippines (8000 ha). The northernmost natural occurrence is on the Ryukyu Islands of Japan and the southernmost in North Australia. In South-East Asia, nipa palm is also cultivated.

It was introduced to West Africa in the beginning of the 20th century and is found in Nigeria and in northern Cameroon as far south as the southern side of the Wouri Estuary (Burns et al., 2002).

Nipa was introduced into West Africa in the early 1900s, specifically, Oron 4.8°N 8.2°E (Nigeria) in 1906 and Calabar (Nigeria) in 1912 (Hutchinson and Dalziel, 1972). It has now spread westwards along the coast down to latitude 4°E. By the early 1990s, nipa had been recognized as a serious invasive 'weed' (see King, 1999). Other oral sources relate that nipa was introduced to check coastal erosion and that it enjoyed total protection by law. There are anecdotal accounts from Nigeria that people were prosecuted and imprisoned by the colonial administration for as much cutting a frond of the palm.

The plant spreads mainly through its fruits floating on water currents to new locations. However, there is the real danger of people carrying the fruits while on a casual visit to the beach and then dropping them at other susceptible sites. The probability of intentional introduction as an ornamental is also very high.

There are two principal modes of spread. The first and more important is movement of water via ocean current and tide; the other is by humans carrying the fruits. Tidal movement has been largely responsible for the infestation of inland rivers and creeks in the Niger Delta, Nigeria. Tidal movements transport the fruits to the near-shore whereas the longshore current moves the fruits generally westwards.

Nipa palm is a tropical plant. The average minimum temperature in its growing areas is 20°C and the maximum 32-35°C. Its optimum climate is subhumid to humid with more than 100 mm rainfall per month throughout the year.

Nipa palm thrives only in a brackish water environment. It is rarely seen directly on the seashore. Optimum conditions are when the base and the rhizome of the palm are regularly inundated by brackish water. For this reason, nipa palm occupies estuarine tidal floodplains of rivers. The optimum salt concentration is 1-9 per mil. Nipa palm swamp soils are muddy and rich in alluvial silt, clay and humus

Growth and Development

After maturing, the fruits are usually pushed off from the infructescence by the developing plumule. They float on tidal water and start growing on a suitable substrate. The radicle is probably aborted and the first root that appears is likely to be the first adventitious root. The seedling is prostrate first, but after being attached to the substrate, the plumule becomes erect and additional adventitious roots arise from the lower part of the stem. In very young seedlings the leaves are arranged distichously but later they become arranged spirally. At first, up to eight bladeless sheaths develop per plant, followed by the first juvenile foliage leaves 3-6 months after germination. During early growth the stem grows obliquely downwards until it is about 1 m deep in the ground (rhizome). About 1 year after germination the rhizome starts branching dichotomously and a new shoot develops vegetatively on each branch. Nipa is a prostrate palm and its growth habit is very similar to grasses. This branching pattern gives rise to the nipa palm 'colony' structure of a mature stand, in which older rhizome parts decay simultaneously and dichotomous divisions produce new shoots. There is also a constant decay of old leaves and formation of new ones throughout the life of a nipa palm, which is estimated to be about 50 years. First flowering occurs 3-4 years after germination. Pollination is effected by flies. In a mature nipa palm stand, normally about one-quarter to one-half of the palms produce flowers or fruits. The fruits mature in 5-9 months. In young fruits the endosperm is liquid, becoming solid in older ones. Frequently, more than one infructescence develops simultaneously per plant. In Papua New Guinea, the weight of one infructescence is 6-30 kg and its circumference 1.1-1.4 m, bearing 88-133 individual fruits.

Other Botanical Information

In South-East Asia, the size of the nipa palm varies: in the Philippines plants are smaller than in Papua New Guinea and Malaysia. In Malaysia, two forms of nipa palms are distinguished, 'nipah gala' and 'nipah padi', differing in the tilt of the leaflets. No cultivars have been developed.

With its prostrate, dichotomously branched stem and its erect inflorescence bearing a terminal head of female flowers and lateral spikes of male flowers, nipa palm occupies a unique position in the Palmae. It has a very long history; possible relations with the genera Pandanus and Sararanga (both from the Pandanaceae) have been suggested.

Ecology

Nipa palm is a tropical plant. The average minimum temperature in its growing areas is 20°C and the maximum 32-35°C. Its optimum climate is subhumid to humid with more than 100 mm rainfall per month throughout the year.

Nipa palm thrives only in a brackish water environment. It is rarely seen directly on the seashore. Optimum conditions are when the base and the rhizome of the palm are regularly inundated by brackish water. For this reason, nipa palm occupies estuarine tidal floodplains of rivers. The optimum salt concentration is 1-9 per mil. Nipa palm swamp soils are muddy and rich in alluvial silt, clay and humus; they have a high content of various inorganic salts, calcium, and sulphides of iron and manganese, contributing to the typical odour and dark colour. The pH is around 5; oxygen content is low with the exception of the topmost layers.

Typically, nipa palm forms pure stands, but in some areas it grows mixed with other mangrove trees. In the understorey some Acanthus, Acrostichum and Crinum species are found.

Nipa palm suffers from few diseases and pests. Rats in Papua New Guinea and pigs and monkeys in northern Borneo may damage the peduncles. In Malaysia, damage of young peduncles by weevils was avoided by removing the rubbery bracts at an early stage of fruit development when preparing the stalks for pretreatment and tapping. Grapsid crab is the main pest of young seedlings.

Nipa impacts negatively on fish catch and shellfish collection. It also impacts negatively on rural navigation in coastal waters.

Nipa threatened Nigeria's extensive mangrove vegetation by displacing the mangrove stands and establishing itself in a mono-specific manner. It reduces the potential for natural mechanisms for control of coastal soil erosion and causes general habitat conversion and biodiversity loss with attendant reduction in biological production potentials of the ecosystem.

Local people depend, often disproportionately on biodiversity for their life support. Loss of biodiversity due to the invasion of plants such as nipa forces migrations and the search for new livelihoods thereby distorting the social structure of the communities.

In South-East Asia, there is a long tradition (hundreds of years) of using palm sap obtained by tapping the inflorescence stalks (peduncle) as a source of treacle (molasses), amorphous sugar ('gula malacca'), alcohol or vinegar. The slightly fermented sap called 'toddy' ('nera' in Indonesia and Malaysia, 'tuba' in the Philippines) is sold and consumed as local beer. In Papua New Guinea, there is no tradition of using the sap. The long, pinnate leaves (fronds) provide material for thatching houses. In the Philippines, Malaysia, Indonesia and Thailand the fabrication of thatching panels, called locally 'shingles', 'pawid' or 'atap', is a significant local source of income. Leaflets and midribs are used for manufacturing of brooms, baskets, mats and sunhats. The white endosperm of immature seeds is sweet and jelly-like, and is consumed as a snack. The cuticle of young, unfurled leaves has locally been used as cigarette wrapping. Various parts of nipa palm are a source of traditional medicines (e.g. juice from young shoots is used against herpes, ash of burned nipa material against toothache and headaches) and material for salt extraction. Some early trials to use the endocarp of mature fruits, called 'plant ivory', for the manufacture of buttons failed because they were vulnerable to attack by fungi, and have largely been replaced by plastic materials. The use of the hard shell (mesocarp) in the making of buttons, necklaces and other fashion apparels is successful in Nigeria. Nipa fronds are commomly used as sails by local fishermen.

Cultural ControlIn Nigeria, no cultural control has been attempted.Mechanical ControlMechanical control involving repeated (three passes) cutting has been successful in the Niger Delta, Nigeria. Plant fronds are cut back three times. The recommended period between each cutting, to assure maximum effectiveness, is 6 weeks. In highly inaccessible locations, the cutting interval may be extended to an absolute maximum of 3 months; beyond this the plants will recover. The equipment used is a regular machete; chainsaws were also used but the increase in operational costs was not justified.Chemical ControlChemical control has not been attempted in Nigeria but some local people have reported limited success when the plant is treated with used engine oil. This is hardly recommended in view of the potential polluting effects.Biological ControlThere are no known natural enemies in the West African (Nigerian) population. No biological control has been attempted in West Africa.

Propagation and PlantingGenerative propagation is by seed (fruit) and vegetative propagation is through dichotomous branching of the rhizome. In Papua New Guinea, the 'pocket and channel' method has been used successfully to propagate nipa palm. It involves placing fruits directly into 10-20 cm deep pockets along the edge of irrigation channels. In the Philippines, seedlings are first grown in a seed-bed and then transplanted into pockets. Spacing is 1.5-2 m, eventually thinned to about 400 plants per ha. Natural stands of nipa palm are usually dense; in Papua New Guinea 2000-5000, in the Philippines up to 10,000 shoots per ha occur.HusbandryWhen utilized for sap production, very dense natural nipa palm stands should be thinned and cleared of old leaf debris. These operations increase the amount of light, improve the flowering frequency, and extend the flowering period. Wider spacings apparently improve production.In palms tapped for sap, the cutting of leaves for thatch will reduce yield. Preferably, old leaves should be cut out before they fall off, because they might injure the peduncles of other palms in their fall.HarvestingTapping of nipa palm can start from the development of the second inflorescence onwards, when plants are about 5 years old. Before sap can be obtained, peduncles must be pretreated or 'gongchanged'. The modality, frequency and duration of this treatment varies. The most detailed and recent account is from Papua New Guinea, where the optimum frequency was four times a week during 10 weeks. The treatment consists of bending the peduncle of the infructescence 12 times, patting along the length of it with hands 64 times and kicking its base four times. The treatment can be performed at various stages of development, starting 2-6 months after flowering. The infructescence is then chopped off. To ensure sap flow the cut surface of the peduncle should be renewed, 'shaved', by slicing 1-2 mm off, twice a day. An internode of bamboo or another container is hung or tied to the peduncle to collect the sap. The duration of sap tapping depends on the length of the peduncle. In Papua New Guinea, the individual peduncle can be tapped for 100 days, in Malaysia for 340 days, in Indonesia for 300 days and in the Philippines for 60 days. Contradictory information exists on the number of peduncles per plant that can be tapped simultaneously. Early studies showed that 2-4 peduncles per plant can be used, but later experience in Papua New Guinea indicates that it is preferable to tap only one per plant. In Nigeria, preliminary studies in sap collection produced discouragingly poor results.When palms are harvested for thatching material, mature leaves may be cut off near the ground, on condition that 2-3 leaves are left on the plant.YieldIn Papua New Guinea, sap yield per shoot in 24 hours is 1.3 litres, in Malaysia 0.47 litres, in Indonesia 2.5 litres and in the Philippines 1 litre. In Indonesia annual sap yield per ha can be 168 500 litres, in Papua New Guinea 169,000 litres, in Malaysia 140,000 litres and in the Philippines 126,000 litres. Cloudy weather decreases transpiration and increases sap yield but high soil salinity has a decreasing effect. Yield also decreases near the nodes of the peduncle; genetic factors may also be involved. Young stands of nipa palm may be higher yielding than old ones, albeit there is no reliable method for estimating the exact age of a nipa palm.It has been calculated that 15-20 t of sugar per ha per year can be obtained from nipa palm as compared with 8-9 t from sugarcane.Handling after HarvestWhen sap is collected in a bamboo container, fermentation starts quickly. The alcoholic fermentation is completed within 30 hours, resulting in an alcohol content of 6.2-9.5%. Thereafter, the spontaneous acetic acid fermentation proceeds. This process is utilized in the Philippines, where vinegar is produced by natural acid fermentation. The acid content, however, remains low (2-3%) as compared with the simple surface film method, using pure Acetobacter species, developed in Papua New Guinea. There, the final acetic acid content was 6.2-7.2% and the product could be diluted to a 4% commercial product.The ease with which sap sugar inverts from sucrose into glucose and fructose, and the beginning of fermentation of the sap, are disadvantages in sugar making. Various methods of inhibiting the inversion have been tested, including sterilizing the bamboo containers by heat and alcohol. The latter was successfully used in Papua New Guinea, where after 17 hours, the alcohol content of the sap was less than 0.5%, a loss of less than 1% of sucrose. Earlier, the addition of lime, potassium or sodium bisulphite or sulphite, copper sulphate or acetate or formaldehyde had been tested.

After maturing, N. fructicans fruit are usually pushed off from the infructescence by the developing plumule. They float on tidal water and start growing on suitable substrate. The radicle is probably aborted and the first root that appears is likely to be the first adventitious root. The seedling is prostrate first, but after being attached to the substrate, the plumule becomes erect and additional adventitious roots arise from the lower part of the stem. In very young seedlings the leaves are arranged distichously but later they become arranged spirally. At first, up to 8 bladeless sheaths develop per plant, followed by the first juvenile foliage leaves 3-6 months after germination. During early growth the stem grows obliquely downwards until it is about 1 m deep in the ground (rhizome). About 1 year after germination the rhizome starts branching dichotomously and a new plant develops vegetatively on each branch. This branching pattern gives rise to the nipa palm 'colony' structure of a mature stand, in which older rhizome parts decay simultaneously and dichotomous divisions produce new plants. There is also a constant decay of old leaves and formation of new ones throughout the life of a nipa palm, which is estimated to be about 50 years. First flowering occurs 3-4 years after germination. Pollination is effected by flies. In a mature nipa palm stand, normally about one quarter to one half of the palms produce flowers or fruits. The fruits mature in 5-9 months. In young fruits the endosperm is liquid, becoming solid in older ones. Frequently, more than one infructescence develops simultaneously per plant. In Papua New Guinea, the weight of one infructescence is 6-30 kg and its circumference 1. 1-1.4 m, bearing 88-133 individual fruits.

Generative propagation of N. fructicans is by seed (fruit) and vegetative propagation is through dichotomous branching of the rhizome. In Papua New Guinea, the 'pocket and channel' method has been used successfully to propagate nipa palm. It involves placing fruits directly into 10-20 cm deep pockets along the edge of irrigation channels. In the Philippines, seedlings are first grown in a seed-bed and then transplanted into pockets. Spacing is 1.5-2 m, eventually thinned to about 400 plants per ha. Natural stands of nipa palm are usually dense; in Papua New Guinea 2000-5000, in the Philippines up to 10 000 plants per ha occur.When utilized for sap production, very dense natural nipa palm stands should be thinned and cleared of old leaf debris. These operations increase the amount of light, improve the flowering frequency, and extend the flowering period as well. Wider spacings apparently improve production.In palms tapped for sap, the cutting of leaves for thatch will reduce yield. Preferably, old leaves should be cut out before they fall off, because they might injure the peduncles of other palms in their fall.Tapping of nipa palm can start from the development of the second inflorescence onwards, when plants are about 5 years old. Before sap can be obtained, peduncles must be pretreated or 'gongchanged'. The modality, frequency and duration of this treatment varies. The most detailed and recent account is from Papua New Guinea, where the optimum frequency was four times a week during 10 weeks. The treatment consists of bending the peduncle of the infructescence 12 times, patting along the length of it with hands 64 times and kicking its base four times. The treatment can be performed at various stages of development, starting 2-6 months after flowering. The infructescence is then chopped off. To ensure sap flow the cut surface of the peduncle should be renewed, 'shaved', by slicing 1-2 mm off, twice a day. An internode of bamboo or another container is hung or tied to the peduncle to collect the sap. The duration of sap tapping depends on the length of the peduncle. In Papua New Guinea, the individual peduncle can be tapped for 100 days, in Malaysia for 340 days, in Indonesia for 300 days and in the Philippines for 60 days. Contradictory information exists on the number of peduncles per plant that can be tapped simultaneously. Early studies showed that 2-4 peduncles per plant can be used, but later experience in Papua New Guinea indicates that it is preferable to tap only one per plant.When palms are harvested for thatching material, mature leaves may be cut off near the ground, on condition that 2-3 leaves are left on the plant.

There are no internationally traded products of nipa palm. The production of thatching material, sugar, vinegar, mats and baskets has only local significance. The sugar, produced in family enterprises in Malaysia and Thailand, is used for confectionery and for small-scale production of distilled spirits. Recently, a pilot scheme was established in West Kalimantan (Indonesia) to produce sugar from nipa palm on a larger scale. It is planned to exploit some 10 000 ha. The production of fuel alcohol from nipa palm was seriously studied in the 1920s in the Philippines and Malaysia, and in the early 1980s in Papua New Guinea. Because of the high input of manual labour required to produce fuel alcohol, the process was not economically feasible in Papua New Guinea, whereas vinegar and treacle showed good potential for cottage-industry development. The quality and price of vinegar produced with the method developed, compared favourably with commercially produced vinegars elsewhere.In Papua New Guinea, sap yield per plant in 24 hours is 1.3 litres, in Malaysia 0.47 litres, in Indonesia 2.5 litres and in the Philippines 1 litre. In Indonesia annual sap yield per ha can be 168 500 litres, in Papua New Guinea 169 000 litres, in Malaysia 140 000 litres and in the Philippines 126 000 litres. Cloudy weather decreases transpiration and increases sap yield but high soil salinity has a decreasing effect. Yield also decreases near the nodes of the peduncle; genetic factors may also be involved. Young stands of nipa palm may be higher yielding than old ones, albeit there is no reliable method for estimating the exact age of a nipa palm.It has been calculated that 15-20 tonnes of sugar per ha per year can be obtained from nipa palm as compared with 8-9 tonnes from sugarcane.When sap is collected in a bamboo container, fermentation starts quickly. The alcoholic fermentation is completed within 30 hours, resulting in an alcohol content of 6.2-9.5%. Thereafter, the spontaneous acetic acid fermentation proceeds. This process is utilized in the Philippines, where vinegar is produced by natural acid fermentation. The acid content, however, remains low (2-3%) as compared with the simple surface film method, using pure Acetobacter species, developed in Papua New Guinea. There, the final acetic acid content was 6.2-7.2% and the product could be diluted to a 4% commercial product.The ease with which sap sugar inverts from sucrose into glucose and fructose, and the beginning of fermentation of the sap, are disadvantages in sugar making. Various methods of inhibiting the inversion have been tested, including sterilizing the bamboo containers by heat and alcohol. The latter was successfully used in Papua New Guinea, where after 17 hours, the alcohol content of the sap was less than 0.5%, a loss of less than 1% of sucrose. Earlier, the addition of lime, potassium or sodium bisulphite or sulphite, copper sulphate or acetate or formaldehyde had been tested.Nipa palm has a good potential for sugar, vinegar and alcohol production. The sugar is already available in the form of sucrose. Sap is in liquid form, so there is no residual bagasse problem as with sugarcane. Nipa palm also occupies lands that are unsuitable for other food crops. Tapping can be carried out all the year round, thus minimizing seasonal labour movement and associated social problems. The disadvantages of exploiting nipa palm include the high demand for manual labour (5 per ha) as compared with sugarcane, and the difficulty of getting machinery into wild stands because of the soft soils and fluctuating water levels. For a nipa palm sugar industry to be developed successfully, non-toxic methods must be developed to inhibit rapid inversion of sucrose and fermentation of the sap. Further research is needed to clarify the physiological mechanisms that regulate sap flow and the effect of pretreating the peduncle. These might prove to be the keys in the effort to decrease the high demand for manual labour in utilizing nipa palm.Potentially, nipa palm might become an energy crop, as it can produce annually about 11,000 litres of alcohol per ha. This is substantially more than the production obtained from sugarcane (5 500 litres) and cassava (1350 litres). But, while prices on the world market for fossil energy remain low, it will not be a serious alternative.

No germplasm collections are available and there seems to be no need for breeding in nipa palm.

N. fructicans has become an invasive weed in Nigeria where it was introduced about a century ago.

There are no internationally traded products of nipa palm. The production of thatching material, sugar, vinegar, mats and baskets has only local significance. The sugar, produced in family enterprises in Malaysia and Thailand, is used for confectionery and for small-scale production of distilled spirits. Recently, a pilot scheme was established in West Kalimantan (Indonesia) to produce sugar from nipa palm on a larger scale. It is planned to exploit some 10,000 ha. The production of fuel alcohol from nipa palm was seriously studied in the 1920s in the Philippines and Malaysia, and in the early 1980s in Papua New Guinea. Because of the high input of manual labour required to produce fuel alcohol, the process was not economically feasible in Nigeria and Papua New Guinea, whereas vinegar and treacle showed good potential for cottage-industry development in Papua New Guinea. The quality and price of vinegar produced with the method developed, compared favourably with commercially produced vinegars elsewhere.

Nipa palm has a good potential for sugar, vinegar and alcohol production. The sugar is already available in the form of sucrose. Sap is in liquid form, so there is no residual bagasse problem as with sugarcane. Nipa palm also occupies lands that are unsuitable for other food crops. Tapping can be carried out all the year round, thus minimizing seasonal labour movement and associated social problems. The disadvantages of exploiting nipa palm include the high demand for manual labour (five per ha) as compared with sugarcane, and the difficulty of getting machinery into wild stands because of the soft soils and fluctuating water levels. For a nipa palm sugar industry to be developed successfully, non-toxic methods must be developed to inhibit rapid inversion of sucrose and fermentation of the sap. Further research is needed to clarify the physiological mechanisms that regulate sap flow and the effect of pretreating the peduncle. These might prove to be the keys in the effort to decrease the high demand for manual labour in utilizing nipa palm.

Potentially, nipa palm might become an energy crop, as it can produce annually about 11,000 litres of alcohol per ha. This is substantially more than the production obtained from sugarcane (5 500 litres) and cassava (1350 litres). But, while prices on the world market for fossil energy remain low, it will not be a serious alternative.