Metroxylon amicarum

Metroxylon amicarum

The Caroline ivory nut palm (Metroxylon amicarum (H.Wendl.) Hook. f., 1884) is an arboreal species belonging to the Arecaceae family.

Systematics –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Plantae,
Subkingdom Tracheobionta,
Spermatophyta superdivision,
Magnoliophyta division,
Class Liliopsida,
Arecales Order,
Arecaceae family,
Subfamily Calamoideae,
Tribe Calameae,
Genus Metroxylon,
Species M. amicarum.
The term is basionym:
– Sagus amicarum H.Wendl..
The terms are synonyms:
– Coelococcus amicarum (H.Wendl.) W.Wight;
– Coelococcus carolinensis Dingler;
– Metroxylon amicarum (H.Wendl.) Becc.;
– Metroxylon amicarum var. majus Becc.;
– Metroxylon carolinense (Dingler) Becc.;
– Sagus amicarum H.Wendl..

Etymology –
The term Metroxylon comes from the Greek μυελός, marrow, and xylon, wood, in reference to the starch present inside the stem and used for food purposes.
The specific epithet amicarum comes from the Latin and means “friends”, referring to the Friends Islands, now Tonga, from where the species was supposed to have originated.

Geographic Distribution and Habitat –
Metroxylon amicarum is a palm endemic to the Caroline archipelago, where it is mainly distributed on the islands of Ponape and Truk.
Its natural habitat is that of humid and rainforests, in freshwater wetlands, coastal or montane areas at altitudes up to 700 meters.

Description –
Metroxylon amicarum is a palm with a massive stem, up to 25 m tall and even 1 m broad, with visible spaced rings corresponding to the insertions of the old fallen foliar bases.
The leaves are very large, pinnate, with a basically vertical habit, up to 10 m long and even 3 m broad.
The leaf segments can reach 150 cm with a width of 10 cm. They are arranged in a V on the rachis but at different angles, a circumstance that gives the leaf a feathery appearance.
The petioles are up to 1 m long and even 30 cm broad, completely covered by characteristic protuberances similar to parallel rings which usually carry, along the whole length, small black spines.
The inflorescence emerges between the petioles of the leaves; it is large, branched, up to 3 m long. The inflorescences are produced continuously during the year and on the same plant we can find flowers and fruits at different stages of maturation at the same time.
The fruits are single-seeded and 9 cm long, extremely hard and covered with shiny brown scales.

Cultivation –
Metroxylon amicarum is an evergreen palm that is very important to the local economy of the indigenous peoples, providing them with food, medicines and a wide range of other materials.
It is commonly harvested from the wild for its many uses, however the plant is also cultivated, mainly for the seed which is used to make buttons.
It is widely cultivated in its places of origin but is not widely cultivated in the rest of the world. Despite the undoubted aesthetic qualities, this species can be admired almost exclusively in the botanical gardens and in the large private collections of the subtropical belt.
This palm is typical of humid, tropical, lowland forests, capable of reaching altitudes of up to 700 meters and more.
It prefers an average annual rainfall between 2,000 and 5,000 mm and does not tolerate more than a short period of drought.
Furthermore, the optimal temperature, annual average, must be around 25 °C with a minimum of 17 °C. It does not tolerate frost, although it can survive in cooler areas of the tropics such as Hawaii, but where it grows more slowly.
It prefers a relatively sunny location and soil wise, it grows well in a wide range of soils, preferring medium to heavy soils with little drainage and pH ranging from 4 to 7.4.
It grows in soils periodically inundated with salt water as long as fresh water flow is prevalent.
The plants are not very tolerant of water shortages, but they also do not like floods except for short periods; they also tolerate strong and salt-laden winds.
Plants usually take 12-15 years to reach flowering maturity from seed, although under ideal conditions this can be reduced to around 10 years. The development of the plant is very fast, given that the stem can grow up to 1 m per year.
Unlike other members of this genus, which flower once and then die, this species is capable of flowering for several years before dying.
Seeds can be transported by water from one island to another.
However, judging by the natural range of the plants, seed viability is likely to be quite reduced in salt water.
Plants usually take 10 to 15 years to reach reproductive maturity.
Propagation is by seed, however the seed quickly loses its viability when stored and does not tolerate drought conditions.
For this reason it is best sown as soon as it falls from the tree and will usually germinate within 1 – 2 months.
Germination is optimal at a temperature of 30°C, although temperatures above 38°C can damage the seeds.
The seeds sometimes germinate while still attached to the infructescence and can reach a height of 90 – 120 cm before falling to the ground.
Germination can be speeded up by removing the seed husk and loosening the cover on the embryo. Care must be taken not to damage the embryo.
The large seed size and rapid initial growth make this species suitable for direct sowing in the field, provided there are constant moisture conditions.
After germination, which can take place in the nursery, it is advisable to immediately transplant the plants even with bare roots. However this plant is able to bear transplants even with much larger dimensions.

Customs and Traditions –
Metroxylon amicarum is a palm endemic to the Caroline archipelago and it is thought that it was probably introduced in some areas of Micronesia, in the prehistoric period or soon after the start of European contact.
This plant is very important for the local economy of the native populations, as it provides them with food, medicines and a vast range of products and materials.
Sago is extracted from the marrow of the tree, a well-known starch which has always been one of the main food sources of the populations of the islands, where it is widely used in the kitchen, above all to prepare typical baked products.
The roots, young leaves and petioles are used in traditional medicine. The parts of the plant are macerated to make poultices to heal skin wounds.
The leaves are used to cover the roofs of houses, which last up to 5 years. The leaf segments are used as straw or woven into mats and baskets.
The stems, although not very resistant, are used as beams for houses and as material for building walls.
The large, very hard seeds such as ivory are used to create a wide variety of carved objects and produce fine buttons.
Among other uses it should be remembered that the large, very hard seeds, similar to ivory, are used to make a series of carved objects and also to make buttons.
The leaves and their petioles have a wide range of applications. In particular, they are a major source of straw.
Additionally, the leaflets can be woven into temporary baskets or used to line cooking pits.
Gourd bottle stoppers are made from lightly rolled discs of sago leaves.
Whole leaves are used to cover and protect dry-stored canoes.
The leaf sheaths are commonly covered externally with rough spines and/or rib-like protuberances. These rough sheaths have served as rasps in the preparation of sago and other food items that need to be grated.
The stiff, hard center ribs can be used to make brooms, can serve as temporary sewing needles or pins, or can be used as skewers for straw sheets.
The smooth inner surface of the sheaths can be used as temporary containers, and as kneading boards for sago.
Children sometimes build surfboards from the base of the petiole (leaf sheath) which can be up to a meter wide.
Boats and rafts are made by children starting from the base of the leaves.
The wood (outer bark) of the trunks is used as flooring and as planking for crossing short streams or marshy areas. The wood is not considered durable or long-lasting, but is used as a by-product by those who mine the starch. Wood has also been used as beams in houses and as a material for walls, although it is rarely used.
The bark can be used as fuel.
Other uses are agroforestry; especially when found on wetter soils, the roots help stabilize the soil by trapping silt.
Young palms, with their many spines, serve as effective barriers to livestock and potential intruders. As palms mature and develop above-ground stems, new palms can be planted adjacent to young ones to maintain the thorniness of the enclosure.
Metroxylon amicarum is classified as vulnerable on the IUCN Red List of Threatened Species (2010).
The threat is consequent to the destruction of the habitat.

Method of Preparation –
Metroxylon amicarum is a very important plant in areas of natural growth or cultivation as practically all of this palm is used.
Among the edible uses, it should be remembered that sago is prepared from this tree.
This is considered a valuable food to take with you on canoe trips; although this palm is less productive than Metroxylon sagu, it is more likely to be seen as a staple food.
The apical meristems or hearts of palm are large and soft. Trees can be harvested before maturity solely for this purpose, using the meristem and several parts of the immature leaves. These palm hearts are used locally or sold in local markets. They are eaten raw as a vegetable or cooked with other foods, often in curries.
Harvesting the heart of the palm leads to the death of the tree as it is unable to produce lateral branches.
Immature seeds are sometimes eaten by children.
The roots, young leaves and stem cork are used in traditional medicine.

Guido Bissanti

Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Useful Tropical Plants Database.
– Conti F., Abbate G., Alessandrini A., Blasi C. (ed.), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.
– Pignatti S., 1982. Flora of Italy, Edagricole, Bologna.
– Treben M., 2000. Health from the Lord’s Pharmacy, Advice and experiences with medicinal herbs, Ennsthaler Editore.

Photo source:
– https://www.palmpedia.net/wiki/Metroxylon_amicarum
– https://pictures.snsb.info/BSMvplantscoll/web/M-0208/M-0208520_20121228_111534.jpg

Attention: The pharmaceutical applications and alimurgical uses are indicated for informational purposes only, they do not in any way represent a medical prescription; we therefore decline all responsibility for their use for curative, aesthetic or food purposes.