Common Name: Agar Wood

General Information

Agar wood is an evergreen tree growing up to 15 metres tall[].
This species is a major source of agarwood, which is very aromatic and highly valued as an incense, perfume and medicine. The plant also provides a useful fibre and wood.
The tree has been overexploited in the wild leading to strong concerns that it could become extinct[]. It is listed as vulnerable by the IUCN[].

Known Hazards

None known

Botanical References

Range

E. Asia - tropical southern China.

Habitat

Lowland forests, sunny places on slopes or along roadsides[].

Properties

Conservation Status	Vulnerable
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	15.00 m
Cultivation Status	Wild

Cultivation Details

Grows best in undulating terrain in the moister lowland tropics, being found at elevations of 200 - 700 metres[]. It prefers an annual rainfall of 1,500 - 6,500 mm, a mean annual maximum temperature of 22 - 28°c and a mean annual minimum temperature of 14 - 21°c[].
Prefers heavy soils developed from gneiss and other metamorphic rocks, but it also grows well on sandy loams developed from sandstone[].
The extremely high prices paid for high quality agar wood and for the essential oil and the indiscriminate felling of both diseased and healthy trees threaten natural stands of Aquilaria including Aquilaria sinensis to extinction. Research into possibilities of artificial induction and stimulation of agar wood formation is therefore urgently required and may offer high economic returns, especially as trials indicate that management of plantations presents no great difficulties. Unless such methods are developed, Aquilaria malaccensis may soon be extinct[].
Plantations have been established, mainly for experimental purposes, to test methods for the induction of agar wood formation[].
Three closely related species of Aquilaria are considered to be the major sources of agar wood and are distinguished by the length of their calyx lobes:-
Aquilaria crassna, which comes from Indo-China, has lobes 12 - 15mm long.
Aquilaria malaccensis, from India, and Malaysia has lobes 2 - 3mm long.
Aquilaria sinensis, from China, has lobes 8mm long.
A number of other species are less important sources of agar wood, including some minor Aquilaria spp., Enkleia malaccensis and the timbers Gonystylus bancanus and G. macrophyllus[].
Agar wood formation is a pathological process taking place in the stem or main branches where an injury has occurred. Fungi are involved in the process, but the process itself is not yet fully understood. Damage by boring insects is often associated with the infection. It is believed that the tree is first attacked by a pathogenic fungus, which causes it to weaken. Infection by a second fungus causes the formation of agar wood, but it is unclear whether it is a product of the fungus or the tree. The fungus implicated in the formation of agar wood in A. malaccensis is Cytosphaera mangiferae, while Melanotus flavolives is assumed to play a similar role in this species[].

Edible Uses

None known

Medicinal

is an astringent, stimulant, tonic herb that relieves spasms, especially of the digestive and respiratory systems, and lowers fevers[].

In Western, Chinese and Indian medicines the incense is used against cancer, especially of the thyroid gland. In China it is applied as a sedative against abdominal complaints, asthma, colic and diarrhoea, and as an aphrodisiac and carminative[].

The grated wood enters into various preparations used especially during and after childbirth, and to treat rheumatism, smallpox and abdominal pains. Decoctions of the wood are said to have anti-microbial properties, e.g. Against Mycobacterium tuberculosis and Shigella flexneri[310

Other Uses

Agar wood is the rare and famous, resin-containing heartwood that is produced mainly from old and diseased trees of several members of this genus[]. In trade a distinction between the wood from these species is rarely made[].
The fragrance produced by the burning agar wood has been highly valued for thousands of years, and its use as incense for ceremonial purposes in Buddhism, Confucianism and Hinduism is widespread throughout eastern and southern Asia. In Thailand it is put into funeral pyres, while in Japan, the incense is used in tea ceremonies[].
Wood only partly saturated with resin but still fragrant, and occasionally also the wood remaining after distillation, is made into sticks called ‘joss-sticks’ or ‘agarbattis’ which are burnt as incense[].
The incense is also used as an insect repellent[].

Agar-wood oil is an essential oil obtained by water and steam distillation of agar wood. It is used in luxury perfumery for application in e.g. oriental and woody-aldehydic bases, ‘chypres’ and ‘fougères’. It produces interesting odour notes with clove oil, e.g. in carnation bases. The oil is so rare and expensive that it is only produced on request[].
Agar-wood oil is a yellow to dark amber, viscous liquid with a characteristic balsamic and woody odour. Its aroma has some resemblance with vetiverol or styrax and has a sweetness similar to that of sandalwood oil. Its odour is long-lasting and exhibits a good tenacity in applications[].

The silvery inner bark can be removed from the trunk in a single large sheet[]. It is highly valued for its strength and durability and is made into cloth and ropes[]. It is also made into writing material which was formerly only used for chronicles of important events and religious books[].

The timber of undiseased trees, known as ‘karas’, is soft and very light with a density of about 400 kg/m3 air dry. It is creamy white to pale yellowish-brown or greyish-brown, heartwood and sapwood not clearly differentiated[]. The texture is rather coarse and the wood diffuse-porous. It is suitable for making boxes, light indoor construction and veneer[].
The scented wood differs from the normal wood due mainly to deposition of an aromatic resin. The resin is concentrated in the included phloem strands. Because of the resin content the scented wood is relatively hard, brittle and heavy[].

Propagation

Seed should be sown immediately, as it remains viable for only about 1 month. It is sown in nursery beds, about 5 mm deep in a mixture of soil, sand and manure and kept under light shade. Germination starts after 10 - 12 days and is normally complete after 1 month[]. Seed sown immediately after collection has about 65% germination, falling to 45% after 1 week and only 5% after 3 weeks in storage[]. The seedlings are very prone to insect attack[]. Seedlings are pricked out into containers 40 - 45 days after germination when they are 3 - 5 cm tall, and are kept under shade[]. They are ready for transplanting when 30 - 35 cm tall and 10 - 12 months old[]. Transplanting bare-rooted seedlings has been tried successfully in some areas[].
Fruit harvested for seed should be collected when mature but still green. A medium- sized tree produces about 2,000 seeds per year, but seed production may fluctuate greatly between years[].
The fruits are dried in the shade for about 2 days, they then burst and release the seed[].

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