Seventy kilograms of wood, no more than twenty millilitres of oil. Agarwood begins with a wounded Aquilaria trunk, passes through years of resin building up, and ends in a very small bottle that needs a permit to cross a border.
The Aquilaria tree and the wound
Undamaged Aquilaria wood has almost no scent. The heartwood is pale and light, and if the tree is never injured it can live its whole life without producing a single piece of agarwood. Agarwood is not the wood of the tree itself. It is the resin the tree secretes when its trunk is wounded or infected by fungi.
The tree belongs to the genus Aquilaria, family Thymelaeaceae. Vietnam has five Aquilaria species; the main source of agarwood is Aquilaria crassna, known locally as dó bầu. On the international market, agarwood also comes from A. malaccensis and A. sinensis. The agarwood page in the Lê Mai library lists all three names.
The wound can come from many things: wind breaking a branch, insects boring into the trunk, a blade. Through that wound, fungi enter the heartwood. Botanical sources often name a fungus of the genus Phaeoacremonium. The tree responds by secreting resin around the infected area, as a line of defence.
That line of defence is what people search for. Wood soaked with resin gradually becomes dense, dark and heavy. In an uninfected tree the heartwood stays pale. One trunk can hold agarwood in one section and plain wood in another, and the harvester cannot see this from outside.
So the scent of agarwood is a scent of response. No injury, no agarwood. The whole agarwood trade, from wild forest to plantation, is built around that simple biological fact.
How slowly the resin forms
Agarwood resin builds up over time, layer by layer, inside the heartwood. There is no fixed timeline for this; it varies with species, type of injury and the condition of the tree. What is certain is that it is slow, and the most heavily resinated wood is usually the wood left undisturbed the longest.
Chemically, agarwood oil is far from most wood oils. The library lists its main constituents as molecules of the chromone group: 2 (2 (4 methoxyphenyl)ethyl) chromone from 21.2 to 33 percent, and 2 (2 phenylethyl) chromone from 16.1 to 23.6 percent. Alongside come sesquiterpenes such as oxo agarospirol and guaiane derivatives, each at a few percent.
Chromones are a group rarely found in ordinary essential oils. They give agarwood oil a heavy, slow evaporating base. The sesquiterpenes add the woody and warm parts. The scent of agarwood therefore does not come from one dominant molecule, as with cassia or star anise, but from a set of compounds whose ratio shifts from one piece of wood to the next.
That variation explains why two bottles of agarwood oil are rarely alike. Same species, different plantation, different year of resin formation, different distillation, different scent. Agarwood has no standard scent in the sense that cinnamaldehyde defines cassia.
Time here is not an extra cost. It is an ingredient. A piece of agarwood is the number of years of resin held in the wood, measured in density and darkness.
Vietnamese agarwood in the history of the aromatics trade
Heavy, dark pieces of wood were once among the most valuable goods passing through the ports of central Vietnam. Agarwood from the forests of Indochina entered the Asian aromatics trade very early, and its name changed with each language: oud in Arabic, aloeswood and eaglewood in English, calambac for the finest grade.
One frequently cited record shows the scale of the price gap. A pound of calambac bought in Hội An for 15 taels of silver could be sold in Nagasaki for 600 taels. The Nguyễn lords later established a state monopoly over the trade in this grade. The exact figures may differ between sources, but the ratio speaks to the place agarwood held in the trade of that time.
In Japan, agarwood has been used in incense ceremony for centuries, and the highest grade is called kyara. In the Middle East, oud is a base material of perfume and incense. These two markets, together with China, are where Indochinese agarwood travelled.
Today the library records agarwood oil as produced mainly in Vietnam, Laos, Cambodia, Bangladesh and India. It remains one of the most expensive aromatic materials, ten to fifteen times the price of jasmine. In 2025 the knowledge of agarwood harvesting and processing in Khanh Hoa was added to Vietnam's national list of intangible cultural heritage.
Western perfumery discovered oud much later. In published note lists, oud appears in Yves Saint Laurent M7 from 2002, Tom Ford Oud Wood from 2007, Byredo Oud Immortel from 2010. Many of these use a reconstructed oud scent rather than real agarwood oil; that is a separate story, told in the piece on the agarwood accord.
The genus Aquilaria and CITES Appendix II
A tree must be wounded to make agarwood, and the fastest way to find agarwood in a forest is to cut the tree down and look inside. High demand combined with that way of harvesting has sharply reduced wild Aquilaria populations. IUCN lists Aquilaria crassna as critically endangered.
CITES is the Convention on International Trade in Endangered Species of Wild Fauna and Flora, signed in 1973, now with 184 member states. It sorts species into three appendices. Appendix I covers species threatened with extinction; commercial trade is prohibited. Appendix II covers species that may become threatened without control; trade requires permits. Appendix III covers species that one country asks others to help control.
Aquilaria malaccensis was placed in Appendix II in 1995. In 2004 every species in the genus Aquilaria was placed in Appendix II, together with the related genus Gyrinops. Since then agarwood chips, powder and oil crossing a border all need export and import permits.
CITES is not an organic or fair trade certification. The library page on certifications gives it a place of its own: a mandatory legal framework, not a voluntary label. For a listed species, paperwork is not decoration. It is the condition for the goods to exist legally on a shelf.
Alongside agarwood in Appendix II sit East Indian sandalwood, Santalum album, since 2003, and Amazonian rosewood, Aniba rosaeodora, since 2010. Three fragrant woods, three stories of overharvesting, one appendix.
Planted, inoculated and wild agarwood
If agarwood is a response to a wound, then the wound can be made on purpose. That is the basis of plantation agarwood. Aquilaria trees are grown in plantations and, once large enough, the trunk is drilled and inoculated to induce the tree to secrete resin. Many inoculation techniques have been developed, with uneven success.
Vietnamese agarwood today comes mostly from plantations. Hương Khê in Hà Tĩnh has over 800 hectares of Aquilaria planted since around 2000. Khanh Hoa and several other central provinces also have plantations. Wild agarwood, formed in forest trees without human intervention, is increasingly rare and sits under strict control from forestry law and CITES.
Three names common on the market need careful reading. Wild agarwood is agarwood formed in trees growing in the wild. Plantation agarwood comes from cultivated trees, whether formed naturally or by inoculation. Inoculated agarwood is agarwood produced by deliberate intervention in the trunk. The name speaks of origin; it does not automatically speak of scent quality.
For a buyer of oil, the practical question is not which kind smells better but which kind has papers. Plantation oil can be traced to a specific plantation, a year of inoculation, a permit. Oil claiming to be wild agarwood without documents is a legal question before it is a question of scent.
Plantations do not erase the conservation story. They only move the pressure away from the forest, provided the paper trail keeps the two sources apart.
Distilled oud oil: scent in layers
Agarwood is chipped finely before going into the steam still. The yield is very low. According to a frequently cited source, seventy kilograms of agarwood give no more than twenty millilitres of oil. That figure explains most of the price of a bottle of oud. Besides distilled oil, CO₂ extracts of agarwood are also produced, with a different scent profile.
Oud oil opens slowly. Because chromones and sesquiterpenes are all heavy, there is no fast top layer as in citrus or leaf oils. On a blotter, what appears first is already wood: dark, resinous, sometimes sweet, sometimes with a fermented edge. The scent changes by the hour rather than by the minute.
In the fragrance family system, agarwood sits in the Woody family. The library describes this family as offering the widest choice of natural materials: cedar for dryness, sandalwood for creaminess, vetiver for earth and smoke, patchouli for depth. Agarwood, guaiacwood and hinoki add their own facets. Agarwood is the deepest and densest facet in that group.
On safety, the library page records no hazards reported for agarwood oil and no known carcinogens. That reflects the data available, not a guarantee. Agarwood oil is rare and costly, so studies are few; the sensible approach is still dilution and a small skin test.
A bottle of oud is the end of a long chain: a wound, years of resin, a drill or a gust of wind, a still, a permit. The scent is only the visible part of that chain.
An unwounded tree gives no agarwood.
The scent is made of injury, time and paperwork, in that order.
However small the bottle, the chain behind it stays just as long.