Common Name: Moluccan Ironwood

General Information

Intsia bijuga is a common medium-sized, unarmed tree with a broad, spreading crown; it can grow up to 40 metres tall. The bole can be 150 - 200cm in diameter, often with small buttresses 2 - 4 metres high and around 2 metres wide[, , , ]. The tree is more or less evergreen, though species within this genus tend to shed their leaves annually and remain bare for a few days of the year[].
Producing one of the most valuable timbers of southeast Asia, the tree is intensively exploited in the wild as a timber species, and is planted in soil conservation projects[]. A moderately fast-growing tree, it makes an excellent ornamental tree for seaside or street planting[], it provides excellent shade[]. It is considered to be a sacred tree in Fiji[].
With few sizeable stands remaining in the wild, the tree has been listed as 'Vulnerable' in the IUCN Red List of Threatened Species(2009)[].

Known Hazards

None known

Botanical References

Range

E. Africa; E. Asia - India, Myanmar, Thailand, Cambodia, Vietnam, Malaysia, Indonesia, Philippines, New Guinea to Australia and the Pacific Islands.

Habitat

Often found on sand and coral beaches, but also in periodically inundated localities further inland[]. It also occurs in dryland mangroves which are the final stage of mangrove forest succession and the transition to inland forests[].

Properties

Conservation Status	Vulnerable
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Semi-deciduous Tree
Height	35.00 m
Growth Rate	Medium
Pollinators	Bees, Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

A plant of the lowland, wet tropics, where it is found at elevations up to 600 metres. It grows best in areas where annual daytime temperatures are within the range 22 - 28°c, but can tolerate 12 - 34°c[]. It is susceptible to frost[]. It prefers a mean annual rainfall in the range 2,000 - 3,000mm, but tolerates 1,500 - 4,000mm[].
Prefers a position in full sun, tolerating some shade[, ]. Prefers a very well-drained, fertile soil[, ]. Plants are very tolerant of saline soils and salt-laden winds[, ]. Prefers a pH in the range 5.5 - 6.5, tolerating 5 - 7[]. Established plants are moderately drought tolerant[].
This species is the national tree of the island of Guam[].
The tree is relatively slow growing and may attain maturity at 80 years[].
Plantation-grown trees can reach a height of 8 - 16 metres within 7 - 8 years, with a diameter about 7.5 - 10cm[].
The tree produces flowers and fruits throughout the year[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

The seeds can be eaten after careful preparation[]. They are traditionally soaked in salt water for 3 - 4 days and then boiled[]. The seedpods are 8 - 15cm long (exceptionally to 28cm) and 4 - 5cm wide (exceptionally 7cm), containing several seeds 20 - 35mm long and wide, and 8mm thick[].

Medicinal

The bark is used in treating persons suffering from a urinary condition (characterised by very dark urine)[]. It is also used in the treatment of rheumatism, dysentery and diarrhoea[]. An infusion of the bark is given to women after delivery[].

Agroforestry Uses:

With its extensive root system, it is a suitable tree for soil conservation and reclamation in eroded gullies and in buffer strips along creeks[].
The tree is also used in water purification[].
The tree is wind tolerant thus ideal as a windbreak[].
The average total annual production of leaf fall is 8,789.4 kg/ha with a high leaf litter decomposition rate. Initial tannin content of the leaf litter is the major chemical factor inhibiting decomposition. High uptake of calcium from the subsoil and its enrichment in the surface soil resulted in higher soil pH under the trees[].

Other Uses

A brown dye is obtained from an oily substance present in the wood and bark[].

The bark is a source of tannins[].

The seed oil repels insects and has been used to protect stored products[]. It is said to compare favourably with neem (Azadirachta indica) extracts[].

When first harvested, the heartwood is yellowish, then it turns rust-coloured and in time assumes a dark colour resembling that of black walnut; it is clearly demarcated from the 5 - 8cm wide band of sapwood.The texture is rather coarse; the grain straight or interlocked. The wood is heavy; hard to very hard; strong; durable, being resistant to fungi and dry wood borers, and moderately resistant to termites and ocean water - it shows an average service life of 6 - 11.5 years in contact with the ground under tropical conditions and 20 years under temperate conditions. It seasons slowly, with only a slight risk of checking and distortion; once dry it is stable in service. The wood works well but has a fairly high blunting effect, stellite-tipped and tungsten carbide tools are recommended; nailing and screwing are good, but require pre-boring; gluing is correct; the wood takes a very fine polish. The timber is highly prized in its local area, where it is used for heavy construction such as bridge making, power pole cross-arms, railway sleepers, boat building, house post beams and furniture. Other items made from the wood are walking sticks, food bowls, canoes and carvings. It is used in constructing the main hull, masthead, maststep and steering oar of ocean-going canoes[, , ].
The small branches of felled trees are used as firewood[].
In former times the tree was considered sacred in Fiji. The bowl for serving the esteemed traditional beverage, yagona, was made from the wood of this tree[].

Propagation

Seed - pre-treatment is necessary because of the hard seed coat[]. This can be done by soaking the seeds for a few minutes in a small amount of boiling water and then leaving in warm water overnight[]. The most effective technique is by the use of a file to scrape off the small protrusion of the seed-coat located opposite the hilum[]. Immersion in concentrated sulphuric acid for a short period also serves the same purpose[].
Seed may be sown directly in the field, germinating well in full sunlight[]. Seeds should be planted vertically with the hilum downward, so that the seed coat is shed as the hypocotyl emerges from the soil[].
Seedlings need high light intensity for optimal growth. They can be transplanted into the field after 3 months[].
Vegetative propagation by means of 60 cm cuttings in the Philippines, had high mortality rates (62%)[].

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