Metroxylon amicarum

Metroxylon amicarum

Metroxylon amicarum is a relatively fast growing palm tree.

In contrast to other Metroxylon species it can bloom more than once.

It is characterized by spiny ridges on the back of the petiole and stem.

On the island of Pohnpei is a very important plant, all parts are used. It is especially valuable as a roofing material.

According to legend, people on Pohnpei used to live in houses without a roof. A woman with magical powers saw this and sent them the oahs (local name for the palm tree) so that they could use the leaves as roofing.

Description:

Metroxylon amicarum spiny ridges

Metroxylon amicarum spiny ridges

Metroxylon amicarum is a palm tree that grows up to 12-33 m high. The trunk is 25 m or longer, 30-36 cm in diameter, prickly.

The dark green leaves are 4-7 m long. The petiole is 1-3 m long, adorned with spiny ridges. The leaves are pinnate, the leaflets are 90-120 cm long. The leaf edge is smooth but sharp edged.

It blooms several years instead of dying after a single flowering like other Metroxylon species. The flowers are borne in a large, narrow axillary inflorescence. Bloom occurs regulary so that there is always fruit on the plant.

The fruit is round, 10-15 cm in diameter. The husk is covered with brown scales. The mesocarp is fibrous, endosperm is white. The embryo is soft when young and later hardens.

Usage:

  • The leaves are used as roofing. They are extremely durable: a thachting of Metroxylon amicarum leaves stays good for about 10 years whereas thatching of other palm species has to be replaced every 1-4 years.
  • Is hardly ever used for the production of sago starch.
  • Immature (and still soft) seed is eaten locally as fruit.
  • The hardened endosperm, called vegetable ivory or ivory nut, is used for making buttons and other small objects.
  • The roots are used in traditional medicine.
Metroxylon amicarum young specimen

Metroxylon amicarum young specimen

Nomenclature:

Common names:

Caroline ivory nut, Caroline ivory nut palm, Polynesian ivory palm, Polynesian ivory nut palm, oahs (Pohnpei), oj (Marshall Islands), rupang, rúpwúng (Chuuk)

Synonyms:

Coelococcus amicarum, Coelococcus carolinensis, Metroxylon amicarum var. majus, Metroxylon carolinense, Sagus amicarum

Etymology:

Metroxylon: from the Greek metra (pith) and xylon (xylem)
Amicarum: from the Latin amicarum (from the friend), for the Friendly Islands (now Tonga)

Origin:

Caroline Islands (Micronesia)



Habitat:

Moist mountain forest, up to 550 m altitude

Hardiness:

USDA zone 10-11

Metroxylon amicarum inflorescence

Metroxylon amicarum inflorescence

Care:

Soil:

Tolerates very different soils, from nutritious to poor, drained but tolerates seasonal flooding, even with salt water.

Exposure:

Sun, light, partial shade. Grows best in full sun.

Water:

Keep the soil moist. Tolerates temporary excess water but no drought.

Temperature:

An average of 25 °C, between 17 °C and over 30 °C

Salt spray:

Tolerates salty air near the sea

Wind:

Is highly wind resistant, rarely damaged even after heavy storms

Metroxylon amicarum fruit

Metroxylon amicarum fruit

Propagation:

From seed. The seeds are ripe after 2-3 years when the husk is brown.

When the seeds are stripped of flesh, they loose their viability fast. Ideally, sowing should be performed up to 1-2 months after maturity. In practice, ripe fruit falls on the ground and is picked there because it is too difficult to climb the palm tree to harvest them or even see from the ground if they are ripe.

The seeds can even germinate in the fruit.

Image sources

Recommended: