Oud-heads and oud newbies, check out the introduction to oud here, which covers everything from how oud is distilled, its uses in oil-based and commercial perfumery, and all about the different markets that consume it. Also, have a read of Part I of this Oud Primer (The Challenges of Oud) while you’re at it.
Part II of the Attar Guide’s Oud Primer looks at all the factors that influence the aroma of oud oil. These include species, geographical region and microclimate (terroir), manner of cultivation, and, last but certainly not least, distillation methodology.
Some factors exert more of an influence than others, and the extent to which a factor exerts its influence varies with each oil. However, all have a role to play in the final aroma, regardless of the largeness or smallness of their role.
Think of it as a slice of genoise sponge with chestnut cream. Tasting it, it is impossible to know which individual ingredient is responsible for the delicious flavor. But you instinctively know that it is not the eggs, nor the sugar, nor the nuts alone that are responsible, but an alchemy that transcends the individual elements.
Let’s get taxonomy out of the way first. The genus is the family of any tree that produces the oleoresin known as oud. Only two genuses of trees in the world produce this oleoresin: Aquilaria and Gyrinops. Gyrinops and Aquilaria are so closely related that biologists used to categorize them as one single genus, but for now, they remain separate. Within the Aquilaria and Gyrinops genuses, there are many different species. The Aquilaria genus consists of twenty-one different species of trees[i], while the Gyrinops genus consists of nine[ii]. (Since species-level taxonomy is an ever-shifting thing, treat these numbers as approximate rather than as absolute).
Within the Aquilaria genus, the most important species of oud-producing trees are the A. Crassna, the A. Agallocha, the A. Malaccensis, the A. Hirta, and the A. Sinensis. There is also the rare Aquilaria Yunnanensis, a species that comes from China and produces very fine oud oil, but is nearing extinction and will not be available in the future. So, when you hear people mentioning Crassna this or Malaccensis that, they are talking about oud oil that comes from a specific species of the Aquilaria tree.
Within the Gyrinops genus, the most frequently-mentioned species of tree are the G. Decipiens, G. Caudata, and G. Walla species. Well, I say ‘frequently mentioned’, but unless you are knee deep in the oud world, it is unlikely that you will have ever stumbled across any mention of these species. They are less well known than the Malaccensis and the Crassnas of this world. The species of the Aquilaria and Gyrinops trees each produces a slightly different type of aroma in the oud oil. Crassnas are generally fruity, for example, with notes of berries and figs an intrinsic characteristic of the species.
The aroma differences between the species are subtle, though. An Aquilaria Malaccensis compared to an Aquilaria Crassna is like a lemon compared to a lime, in that although they smell and taste subtly different to one another, you can still tell that they are both citrus. Just like you can tell that Cabernet Sauvignon and Cabernet Franc, though different varieties of wine, belong to the same family.
Geographical Region & Microclimate (Terroir)
The region in which a tree grows is an important indicator of how oud oil will smell. Not because oud oil recognizes country borders but because of the different microclimates in those regions. For example, oil distilled from resinated wood grown in the steamy jungles of Papua smells very different to oil from trees in Assam, in Northern India, even if the trees come from the same species. Roughly speaking, this is the concept of terroir.
Terroir is the total effect of the natural environment on the oud. Here, ‘environment’ is understood to mean the microclimate – the combination of physical terrain, humidity, temperatures, water quality, wind conditions, and air purity unique to a specific place. Terroir was a concept that grew up around wine, but it has now been expanded to include any crop whose character is shaped by the place in which it has grown. In addition to wine, examples of crops influenced by terroir include coffee, chocolate, chili peppers, tea, and tobacco.
And oud, of course. Plant one Aquilaria Sinensis tree in Borneo and another in Vietnam, and because of the differences in micro-climates, soil, air pollution, exposure to natural or man-made viruses and traumas, and even the quality of the local water used for distillation, the oud oils produced from these trees will likely smell slightly different from one to another, even though they come from the same species. Some consider terroir to be a more significant factor in determining how an oud oil will smell than its biological species or genus. In other words, nurture over nature. It is likely to be more complicated than that, however. Oud oils are reflective of a great many factors, of which terroir is just one.
The following terms describe the most common terroirs in the oud world: Cambodian (mostly written as ‘Cambodi’), Indian (also called Hindi, Bangladeshi, or Bengali), Malaysian, Indonesian, Papuan, and Borneo (formerly Kalimantan).
Less common geographical denominations of oud oils are Laotian, Vietnamese, Sri Lankan, and Chinese. The boundaries between what is considered a genuine terroir (referring to a specific place or microclimate) and a style of oud (referring to the hand of man steering the aroma in one direction or the other) are complex and ever shifting. The matter of terroir versus style will be discussed in detail in the next chapter of the Oud Primer.
Manner of Cultivation
There are two main categories of cultivation of agarwood: wild and plantation.
Wild oud cultivation, as the name suggests, means agarwood trees growing wild in the jungles of India and the Far East, with no human intervention beyond harvesting. Wild trees develop the oleoresin that we call oud in response to a naturally-occurring fungal infection. Oleoresin production in wild trees can be triggered in response to any external trauma, including invading insects, strafing of the bark by harsh weather that opens up ports in the skin, volcanic eruptions, and even bullets.
There was an interesting theory floating around a while back that kyara – the most prized type of resinated wood from very old trees in Vietnam – might in fact have originally been formed in response to the trees being struck by hails of bullets during the Vietnam war. A young scientist conducted tests on trees in the region that had seen heavy fighting during the Vietnam War. He found that bullets embedded in the grain had sulphurized over the years and it was these trees that yielded the best Kyara[iii].
The temptation to believe this story is strong, perhaps because it suggests that the most extreme beauty in life arises from the most extreme trauma. Unfortunately, the idea is more romantic than credible, given that genuine Kyara is much older than the timeline suggested by the scientist: over a hundred years compared to the fifty-odd years since the beginning of the Vietnam War.
There is very little wild oud left, however.
First, because at an 8% inoculation rate the natural occurrence of oleoresin in wild Aquilaria and Gyrinops trees is low to begin with, meaning that oud hunters are looking for eighty infected trees in every thousand trees.
Second, because deforestation driven by the need to clear land for livestock or cash crops means that wild agarwood trees are getting mowed down too. As Trygve Harris notes, deforestation is happening all over Southeast Asia despite the presence of agarwood trees rather than because of them[iv]. Couple a naturally hard-to-find resource with high niche market demand and in-country competition for land, and that CITES classification of agarwood as an endangered species begins to make sense.
The only viable alternative thus far to the fast-disappearing wild oud is plantation cultivation. On plantations, agarwood trees can be grown under controlled conditions. As opposed to wild trees, which are infected by natural viruses, bugs, etc., trees grown on plantations are artificially infected with the fungus that makes them produce oleoresin. In other words, the infection rate is controlled.
The trees are inoculated using one of three methods, as follows: (i) stripping off a section of bark, wiping the fungus on with a stick, and then replacing the bark, (ii) poking (infected) bamboo sticks into drilled holes in the trunk, or (iii) injecting the tree with a syringe of a chemical fungus. The resin will begin forming soon after the fungus is introduced.
The incidence of infection and subsequent development of oleoresin on plantations is 100% compared to the 8% in the wild. One might argue that nature does best when left to her own devices. But realistically, man cannot leave well enough alone – especially when it comes to a resource as vital to the economy as agarwood.
Artisan oud distillers also do not use or encourage chemical inoculation. Instead, they instruct their farmers to cut holes into the tree and wait for natural, airborne fungi and bugs to infect the tree. Oud oil distilled from agarwood inoculated in this manner is called organic oud, to emphasize that only natural inoculation methods were used to produce the oleoresin, not chemicals.
Typically, farmers under contract to deliver a cash crop to the big perfume houses and distributors will begin to harvest the trees for oleoresin between six months and three years from the date of inoculation[v]. This is in marked contrast to wild trees, where the oleoresin may be anywhere between twenty to a hundred years old when it is harvested. It also differs from the harvesting of organic farmed oud, because artisan distillers are careful to only use wood from trees that are already fully-grown, i.e., between twenty and forty years old.
There are huge advantages to plantation cultivation over wild oud. First, oud oil from plantation-grown trees can be produced in reliably large quantities, because the infection rate is a hundred percent. Second, the quality and smell of the resulting oil is consistent, due to the species, microclimate, and cultivation techniques being the same from tree to tree. Plantation oil therefore removes the two main problems the commercial perfume sector faces when using pure oud oil, which are replicability and scalability. Sustainability also means more income for local farmers, as well as less physical danger and livelihood insecurity for the hunters who go into the jungles to search for wild oud.
Houses that use plantation oud are Mona di Orio, The Different Company, Maison Francis Kurkdijan, Dusita, and Fragrance du Bois, the latter a brand that owns its own sustainable oud plantation in Thailand. Most of the artisan distillers, like Ensar Oud, Agar Aura, FeelOud, Al Shareef Oudh, and Imperial Oud, also distill organic plantation oud oil, alongside their stock of wild oud oil. For any brand who stakes its reputation on high quality products, it is crucial to be able to monitor and control keys parts of the farming, harvesting, and distilling process.
However, there are also disadvantages to plantation-cultivated oud.
First, there is the crucial matter of aging. The oleoresin harvested from plantation trees is very young, and in terms of scent, can never be as beautiful or as spiritually moving as oleoresin that has been growing in a wild tree for ninety years. Think a young, rough Retsina versus a mature Burgundy.
Second, many connoisseurs report that plantation oud oil is not nearly as satisfying to wear as wild-crafted oud because it contains some off-puttingly sour or metallic characteristics, probably connected to how the trees were inoculated. Of course, this is not the case for most artisanal organic oils, which are produced in a specific way to avoid these off-putting characteristics.
Trygve Harris notes that the younger plantation wood ‘is ok. The oil can be adequate. And this is what people want, this farmed agarwood. It is the only possibility now anyway as the wild wood is gone. Here in the Gulf, the quality is also much lower — even some people who can buy what they like have changed their taste or made do with what is available’[vi].
Plantation oud oil is generally most valuable in the setting of exclusive commercial perfume where it is used as one note among many, rather than for wearing neat on the skin. The importance of plantation oud to the niche and commercial perfume sector cannot be understated. For wearing neat on the skin, however, it is best to stick to either wild-crafted oud oil or artisanal, organic oud oils produced by individuals or brands that you know to have rigorous quality control or in situ management of the farming process.
The quality and oleoresin content of the wood that goes into the still is only one part of the equation. The other part is distillation technique. You might have the best oud wood in the world but ruin it through hasty distillation, dirty equipment, poor knowledge, or lack of skill. Conversely, a gifted distiller will be able to wrest an astonishing range of nuances from a still filled with low-to-medium quality oud wood.
All of the following factors will affect how the oud oil smells, and can therefore be experimented with to produce different results:
- the length of the pre-soak
- force-aging (exposing the oil to air)
- maturation in the bottles
- the mineral content of the distilling water
- the materials of the still (copper versus steel)
- the quality of the tubing (clean versus dirty, rubber versus plastic), and;
- the cooking temperatures in the still.
For example, technically, you could take wood from Malaysia or the island of Borneo and turn it into an oil that has all the characteristics of a Hindi (animalic, smoky, fermented), all through simple adjustments to the distillation methodology such as lengthening the soak times, using steel drums, cooking at high temperatures, and force-aging the oil.
Similarly, a skillful distiller, under direction from an artisan oud producer such as AgarAura or Ensar Oud, can coax kyara-like nuances from wood that, while excellent quality, is neither from an Aquilaria Sinensis tree, nor even from Vietnam. In a way, distillation is a bit like alchemy – turning wood into gold. Or, in the wrong hands, into lead.
About Me: A two-time Jasmine Award winner for excellence in perfume journalism, I write a blog (this one!) and have authored many guides, articles, and interviews for Basenotes. (My day-to-day work is in the scientific research for development world). Thanks to the generosity of friends and acquaintances in the perfume business, I have been privileged enough to smell the raw materials that go into perfumes and learn about the role they play in both Western and Eastern perfumery. Artisans have sent vials of the most precious materials on earth such as ambergris, deer musk, and oud. But I have also spent thousands of my own money, buying oud oils directly from artisans and tons of dodgy (and possibly illegal) stuff on eBay. In the reviews sections, I will always tell you where my sample came from and whether I paid for it or not.
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Photo: Two pieces of wild Borneo agarwood in my collection, photo my own (please do not use without crediting me)