Nypa fruticans Wurmb

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. Leaves in tufts of 3-5 per plant, 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 6 perianth parts similar for both sexes; male flowers with 3 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 1 carpel, compressed and irregularly angled, pyramidal, 10-15 cm 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. 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, 2 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 is considered an advanced palm species, with a very long history; possible relations with the genera Pandanus L.f. and Sararanga Hemsley (both from the Pandanaceae) have been suggested.

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 flowers or fruits randomly. The fruits mature in 5-9 months. In young fruits the endosperm is liquid, becoming solid in older ones.

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.

Nipa palm is a tropical plant. Its optimum climate is subhumid to humid. 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. 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 is one of the oldest angiosperm plants and probably the oldest palm species. Eocene and miocene fossil findings 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 deg. N-10 deg. S, stretching from Sri Lanka through South-East Asia to North Australia. It was introduced to West Africa in the beginning of the 20th Century. The largest natural nipa stands are found in Indonesia (700 000 ha), Papua New Guinea (500 000 ha) and the Philippines (8 000 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.

Generative 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.

Plantation: 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. Husbandry: 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.

Pests: 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.

Food: 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. The white endosperm of immature seeds is sweet and jelly-like, and is consumed as a snack. Medicine: 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 headache) and material for salt extraction. Other products: 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 cuticle of young, unfurled leaves, has locally been used as cigarette wrapping. 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."