Metroxylon sagu Rottboell
Family
Palmae
Synonyms
Metroxylon rumphii Mart. with many varieties, designated by Beccari; Metroxylon squarrosum Becc. with many varieties.
Vernacular Names
| Malaysia | Rumbia (General), balau (Melanau, Sarawak). |
| English | True sago palm, sago palm. |
| Indonesia | Pohon sagu, pohon rumbia (General), kirai (Sundanese), lapia (Ambonese). |
| Papua New Guinea | Sak-sak (Pidgin). |
| Philippines | Lumbiya. |
| Burma (Myanmar) | Tha-gu-bin. |
| Cambodia | Chraè saku. |
| Laos | Sa:kh’u: tônz. |
| Thailand | Sakhu. |
| Vietnam | Sagu. |
| French | Sagoutier. |
Note: In the Indonesian-Malay language region, the word ‘sagu’ denotes the edible starch from the pith of any palm and each of these palms may be called ‘pohon sagu’ (sago tree). ‘Pohon rumbia’ designated one of them, namely the ‘true’ sago palm dealt with here, but the name is not commonly used.
Geographical Distributions
Metroxylon sagu probably originated from Papua New Guinea and the Moluccas but has only recently been dispersed for research beyond Southeast Asia and the nearby Pacific islands. In Indonesia, the palm is now found in parts of Sulawesi, Kalimantan, Sumatra and West Java, as well as on many smaller islands with a non-seasonal climate, notably the Riau islands, Nias and the Mentawai islands.
In Malaysia, the palm grows in Sabah, Sarawak and on the Peninsular. Some are found in Brunei and in the Philippines (Mindanao). There are large areas of M. sagu in Papua New Guinea as well as in a small area in southern Thailand. M. sagu is found at least as far as east the Solomon islands and probably the Santa Cruz islands (species have not been identified with certainty). The world’s largest contiguous M. sagu swamps and forests are found in Papua New Guinea, totaling a roughly estimated 5-6 million ha, with 4-5 million ha on the Indonesian part of the island.
Description
M. sagu is a medium to tall palm tree, flowering only once, romonoecious and forms basal suckers.
The roots are spongy but with a tough central fibro-vascular strand but not extending to great depth (80-100 cm in a peat soil). The pneumatophores (air roots) are present.
The trunk is 30-60 cm in diametre and measures 7-20(-25) m tall. The lower part is ringed with leaf scars while the upper part is covered with semi-persistent leaf sheaths. The epidermis is thin, very sclerenchymatous, surrounding the fibrous bark and measures 5-10 mm thick. Under the bark is an extremely hard layer of sclerenchymatous fibre bundles, measures up to 1 cm thick that surrounds the parenchymatous pith.
The leaves are 18-24 in vigorous trunked palms, simply pinnate and measure 5-7 m long (sometimes up to twice as long). The petiole is very robust and widening at its base into a stem-clasping sheath. The sheath and petiole are unarmed or armed to various degrees with needle-like spines, measure up to 22 cm long and arranged in transverse combs. The leaflets are up to 200 per leaf, measuring 50-160 cm x 3-6(-9) cm, often with small spines along the margins and on the midrib and sometimes with an apical, slender appendage, usually valvate margins and reflexed.
The inflorescence is apparently a terminal panicle, measures 3-5(-7.5) m high and wide. The first-order branches are (10-)15-30 and straight to curving upward. The flower-bearing third-order branches are spadix-like, rust-coloured when young, darker and redder from densely packed bulging flower buds later. The flowers in pairs are arranged spirally where each pair consists of one male and one hermaphrodite flower, but up to half of the buds, usually most of them are male and may abort before they reach anthesis. The bracts of the first to the third order are smooth to spinulescent outside. The flowers are with 3-merous and 6 stamens.
The fruit is a depressed-spherical to obconical drupe, measuring 3-5(-7) cm in diametre, covered with 18(-19) vertical rows of scales, rhomboid, pointing downwards, greenish-yellow and turns straw-coloured towards or after fruit fall. The scale layer is lined inside with a white spongy layer.
The seed is nearly spherical, measuring about 3 cm in diametre and firmly embedded in the shiny cream-coloured firm flesh which turns pinkish when exposed to the air. The testa is dark brown. The endosperm is homogeneous and horseshoe-shaped in longitudinal section because of large chalazal cavity. The seeds are often failed to develop, resulting in fruits filled with the cream-coloured flesh only.
Ecology / Cultivation
M. sagu is a tree of the per-humid tropical lowlands, occurring naturally up to 700 m above sea level (up to 1200 m in Papua New Guinea). The best conditions for M. sagu growth is an average temperature of at least 26°C, a relative humidity of 90% and an irradiance of about 9 MJ/m2 per day. Natural stands of M. sagu palm occur on swampy coastal plains, river floodplains and higher up on flat valley floors. When growing downstream along rivers, tidal influences may be part of the habitat of M. sagu, and may affect the level and salinity of flood water or groundwater. Daily flooding is harmful to the seedling growth, as the salinity corresponding to electric conductivities (EC) is over 1 S/m. EC of sea water is 4.4 S/m.
Occasional flooding, even with very saline water is tolerated. Although found on mineral, peat and muck soils, M. sagu grows best on mineral soils with a high organic matter content (up to 30%). In New Guinea, M. sagu occurs mainly in 4 vegetation types. Ranging from land inundated most of the year to less flood-prone lands, one may successively encounter M. sagu such as Phragmites swamp (groves of trunkless sago palms in dense stands of the reed Phragmites karka (Retz.) Trin. ex Steud.), M. sagu swamp (dense stands of sago palms, most of them trunkless), and M. sagu forest (sago palms in various stages of development mixed with dicotyledonous trees in various proportions). On the peat soils that are dry most of the year, Campnosperma–M. sagu forest (sago palms forming an understorey under a closed canopy of Campnosperma brevipetiolatum Volkens) can be found. The most numerous and largest trunks are found in the sago palm forest. As the water becomes more brackish, M. sagu often borders on stands of the more salinity-tolerant nipa palm (Nypa fruticans Wurmb).
Line Drawing / Photograph
References
- Plant Resources of South-East Asia No. 9: Plants yielding non-seed carbohydrates.
