Agarwood: A Fascinating Journey through its Origins, Species, and Cultivation
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Mark, a young man with a Western background, had always been fascinated by the power of scents. Ever since childhood, he loved to smell things and found that odours played a crucial role in his memories and emotions. Mark believed that scents could connect him to nature and help him achieve a higher sense of self. As he grew older, his interest in scents only deepened, and he began exploring various fragrances worldwide.
In his quest for unique and captivating aromas, Mark stumbled upon agarwood, a rare and precious fragrant wood derived from the Aquilaria tree. He was immediately captivated by its rich, complex scent and found that it resonated deeply with him. Mark felt that the aroma of agarwood brought him a sense of inner peace and connected him to the spiritual world.
However, Mark soon discovered that obtaining genuine agarwood was no easy task. The Aquilaria trees from which it was harvested were considered endangered in the wild, and their deforestation was causing ecological concerns. Mark was conflicted; he wanted to experience the incredible scent of agarwood without contributing to environmental damage.
Additionally, Mark found that the market for agarwood products was fraught with scams and adulterated oils. Unscrupulous vendors were taking advantage of the high demand and rarity of agarwood, selling counterfeit products to unsuspecting buyers. Mark struggled to find a reliable source for high-quality agarwood that aligned with his values and passion for nature.
After months of research, Mark discovered a small, family-owned farm that practised sustainable agarwood cultivation. The farm offered a one-stop shop for all agarwood products, including chips, incense, beads, and oils in various grades. Despite its remote location, the farm was committed to minimising its environmental impact and providing authentic agarwood to enthusiasts like Mark.
Through faith, we met, thanks to the power of the Internet or search engines.
Mark was thrilled to find a source of agarwood that allowed him to enjoy the fragrance without contributing to deforestation. He ordered a small batch of products from our family farm, eagerly awaiting their arrival. When the package finally arrived, Mark could not be happier. The rich, captivating scent of the agarwood products enveloped him, transporting him to a realm of serenity and spiritual connection.
He asked me many questions, which prompted me to write this article. Although some points were covered in some of my previous blogs, there was something new that I learnt too.
Agarwood: A Fascinating Journey through its Origins, Species, and Cultivation
Throughout history, odours have played a significant role in human life, influencing various aspects of culture, religion, and social practices. Fragrances have been used for personal grooming, religious ceremonies, and medicinal purposes, contributing to both physical and emotional well-being. Agarwood, in particular, is an excellent example of how odours have held importance in human life across different cultures and periods.
Agarwood, also known as oud, is a highly valued fragrant wood derived from the Aquilaria tree. When a specific type of mould infects the tree, it produces a dark, resinous heartwood with a unique and highly sought-after scent.
The rarity and distinctive fragrance of agarwood have made it an essential element in various religious and cultural practices throughout history.
The Early Uses of Agarwood
The first scientific record of agarwood usage was likely that of Avicenna, an Arab physician (980–1037), who described several types of agallochum. Among the different types of agallochum, he recorded two names, xylaloes and agalugen. The wood was used for its fragrance and had several applications in different societies throughout history. In the Malayan region, it was known as agila, while in India and Arabia, it was called aod-i-kimaree. Agarwood has been used for centuries as a valuable product for trade, particularly between the Chinese, Malacca, and Sumatra regions ( (Lee, S.Y., Mohamed, R. (2016))Biblical references to agarwood, “aloes”, are believed to be related to Aquilaria agallocha and Aquilaria malaccensis species. While agarwood was known in the pre-Islamic world, its popularity surged as a highly sought-after perfume and incense during the early Islamic period.
An Introduction to Agarwood Species
Botanically, the tropical evergreen agarwood species belong to the genus Aquilaria and the family Thymelaceae. There are eight species within this genus from which agarwood perfume can be extracted, with the four principal species being Aquilaria Sinensis, Aquilaria malaccensis, Aquilaria agallocha, and Aquilaria crassna. Contrary to common misconception, agarwood, or aloeswood, should not be confused with aloe vera, a fragrance-less purgative plant.
My friend is an Agarwood distiller, he lives close to the border of Malaysia and Brunei. He shared his knowledge with me about Aquilaria Malaccensis.
The Aquilaria Malaccensis tree is well-known and valued for its special scented wood called agarwood, which is also known as aloeswood, eaglewood, and gaharu. When the tree gets hurt or feels stressed, it produces a unique-smelling resin. This happens because the injury lets in germs that make the tree's wood produce the resin to protect itself. The resin then changes the wood into agarwood.
The tree's structure helps it create this aromatic resin. The tree's wood comprises different types of cells that store food, transport chemicals, and produce resin. When the tree is infected or hurt, the resin gathers in these cells, changing the wood's smell, colour, weight, and hardness.
Agarwood has many uses, including perfumes, incense, medicine, and religious practices. Because it's in high demand, the tree has become rare due to overharvesting. It has been listed as a threatened species since 1995. Today, people grow the tree in small farms, large plantations, or even their own backyards for its valuable agarwood and other products.
Here is a summary of the 21 Aquilaria species, their origin, and conservation status according to the provided table in the book of Agarwood: Science Behind the Fragrance (Lee, S.Y., Mohamed, R. (2016))
Critically Endangered:
- Aquilaria crassna: Cambodia, Laos, Thailand, Vietnam (1998)
- Aquilaria rostrata: Malaysia (2012)
Vulnerable:
- Aquilaria banaensae: Vietnam (1998)
- Aquilaria beccariana: Brunei, Indonesia, Malaysia (1998)
- Aquilaria cumingiana: Indonesia, Philippines (1998)
- Aquilaria hirta: Indonesia, Malaysia, Singapore (1998)
- Aquilaria malaccensis: Bangladesh, Bhutan, India, Indonesia, Iran, Malaysia, Myanmar, Philippines, Singapore, Thailand (1998)
- Aquilaria microcarpa: Indonesia, Malaysia, Singapore (1998)
- Aquilaria sinensis: China (1998)
Conservation Status Unknown:
- Aquilaria apiculata: Philippines
- Aquilaria baillonii: Cambodia
- Aquilaria brachyantha: Philippines
- Aquilaria citrinicarpa: Philippines
- Aquilaria decemcostata: Philippines
- Aquilaria filaria: Indonesia, Philippines
- Aquilaria khasiana: India
- Aquilaria parvifolia: Philippines
- Aquilaria rugosa: Thailand, Vietnam
- Aquilaria subintegra: Thailand
- Aquilaria urdanetensis: Philippines
- Aquilaria yunnanensis: China
These Aquilaria species are mainly found in Southeast Asia and are known for producing agarwood, which is used in various industries, such as perfumery, incense, and traditional medicine. Many of these species face conservation challenges due to habitat loss and overexploitation.
Agarwood Resin Formation Factors in Aquilaria Trees
Causes of Agarwood Formation
Research suggests that Aquilaria trees create agarwood when they are hurt or infected in response to attacks from harmful organisms or stressful situations. Stress can come from lightning strikes or fires, while injuries and fungal invasions can happen due to cutting, drilling, natural damage, or animal grazing. In natural forests, agarwood is found in the stems of old trees, broken branches, knots, and injured parts.
Agarwood Production Techniques
Given that only 7% of trees are naturally infected by the required fungi and that the resin-producing process can take centuries, agarwood resin is an increasingly rare resource. High demand has led to overexploitation, resulting in the International Union for Conservation of Nature classifying the tree as vulnerable and the Convention on International Trade in Endangered Species of Wild Fauna and Flora placing it in Appendix II. To protect these trees for future generations, several countries have implemented restrictions on extraction.
As only a small percentage of trees contain agarwood and even less can be processed into raw agarwood, researchers try to make planted Aquilaria trees produce agarwood earlier to speed up harvesting. To do this, they use techniques such as inoculation (injecting the trees with substances), combining inoculation with artificial wounding, and artificial wounding alone. Different methods of applying inoculation and wounding have been tried, but agarwood from farms is often considered lower quality than that from natural forests.
It is not accurate to assume that agarwood from farms is always of lower quality than that from natural forests. The quality of agarwood is influenced by various factors, such as the age of infection, as well as the infection process and environmental conditions.The age of infection refers to the duration that the Aquilaria tree has been infected, which plays a crucial role in determining the quality of agarwood. An older tree that has been infected for a longer time will generally produce higher-quality agarwood, as the resin has had more time to develop within the tree.
In some cases, agarwood produced in farms can be of equal or even higher quality than that from natural forests. This is because farmers can control and monitor the wounding and infection process, ensuring that the tree has enough time to produce resin-rich wood. Additionally, farmers can provide the trees with optimal conditions for growth and infection, further improving the agarwood's quality.
Factors Affecting Agarwood Formation
Many factors influence agarwood formation and quality, including:
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Infections if the trees are injured
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Stress conditions like lightning strikes, fires, or injuries
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Tree species and genetic differences
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Tree age
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Location and elevation where the tree grows or is planted
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Soil type and habitat
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Microclimate
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Seasonal changes
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Environmental changes
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The region where the tree comes from
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Types of fungi and bacteria attacking the trees
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Tree processes related to the immune system and defence mechanisms that produce essential oil
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Endophytes (organisms) living in the tree
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Location within the tree where agarwood is formed or collected
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Length and intensity of light exposure in treated wood
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Inoculation methods
1. Infections if the trees are injured
Agarwood is formed due to infection after wounding or other processes. Non-resinous wood is odourless, yellow-whitish, soft, and low in density. Fungi are thought to cause an immune reaction in the wood, leading to the production of agarwood oleo-resin. Dark fibers on the wood stem surface can sometimes indicate agarwood, but the tree has to be cut down to confirm its presence.
2. Stress conditions like lightning strikes, fires, or injuries
Agarwood formation can be triggered by trees being naturally infected, stressed, struck by lightning, injured, or mechanically wounded. The resin is produced in the wood as a chemical defence against pathogens, and secondary metabolite compounds suppress and inhibit the development of these harmful organisms.
3. Tree species and genetic differences
Different Aquilaria species may produce varying qualities of agarwood resin. The presence of agarwood in trees can be difficult to determine. Still, some external features may indicate its occurrences, such as a poor crown, decayed branches, uneven bole, or the appearance of ants in the fissures.
4. Tree age
According to Naziz, P. S., Das, R., & Sen, S. (2019), age plays a significant role in the formation of agarwood in Aquilaria trees. Healthy trees do not produce fragrant compounds, and the development of agarwood is consistently associated with mechanical injury, insect attacks, and microbial infections in plants that have reached a certain age. Infected trees start producing resin from the age of 15 years, and trees aged 50 years or more yield the highest quality agarwood (Chakrabarty et al., 1994).
In a study of A. malaccensis trees from Northeast India, only 7.14% of trees below 8 years old were infested by the insect Z. Conferta. The highest infestation rate (34.13%) was observed in trees aged 8-16 years, while 13.40% of trees above the age of 16 years were affected. This data indicates that tree age significantly impacts the likelihood of agarwood formation, with older trees generally producing more agarwood.
5. Location and elevation where the tree grows or is planted
Slope: 0-75 degrees
- Agarwood trees can grow on various slopes, from flat ground (0 degrees) up to steep inclines (75 degrees). This adaptability allows them to thrive in diverse terrain and landscapes.
Mean annual temperature: 19-25°C
- Agarwood trees prefer a moderate to warm climate, with average yearly temperatures ranging from 19°C to 25°C. These temperatures are ideal for the tree's growth and survival, enabling them to flourish in tropical and subtropical regions.
Elevation: 90-1,300 meters above sea level (asl)
- Agarwood trees can grow at elevations ranging from 90 to 1,300 meters above sea level. This range indicates that they can thrive in both lowland areas and mountainous regions, giving them the flexibility to adapt to various altitudes.
Mean annual rainfall: 2,000-5,500 mm
- These trees need ample water for optimal growth, with an average yearly rainfall of 2,000 to 5,500 millimetres. This range ensures that agarwood trees receive enough water to support their growth and development throughout the year.
- Soil type and habitat
The ideal soil type for Agarwood forest growth is slightly acidic soil, with a pH that is somewhat below 7. This type of soil supports the healthy growth and development of Agarwood trees. Additionally, Agarwood trees thrive in areas with an annual rainfall ranging from 2,100 to 5,500 mm and a mean annual temperature between 19°C and 25°C. These specific climate conditions are conducive to the growth and formation of Agarwood resin, which is highly valued for its unique fragrance and medicinal properties.
7. Microclimate
The microclimate refers to the local atmospheric conditions within a specific area that can differ from the broader climate of a region. Microclimatic conditions, such as temperature, humidity, and rainfall, can have a significant impact on Agarwood formation and quality. The following factors explain how microclimate influences Agarwood:
- Temperature: The mean annual temperature range of 19-25°C is essential for the growth and formation of Agarwood. Temperature fluctuations within this range can affect the physiological processes of the tree, including its response to stress and infection, which in turn influences resin production.
- Humidity: High humidity levels can promote the growth of fungi and bacteria, which play a critical role in the formation of Agarwood. The interaction between these microorganisms and the tree's immune response triggers the production of oleoresin, leading to Agarwood formation.
- Rainfall: An average annual rainfall of 2,100-5,500 mm is vital for Agarwood tree growth. Adequate water supply not only supports healthy tree development but also influences the tree's susceptibility to pathogens and its ability to produce oleoresin.
- Soil moisture: The microclimate also affects soil moisture content, which influences the tree's overall health and its ability to produce agarwood. Proper soil moisture is necessary to grow beneficial microorganisms that help form agarwood.
- Light intensity: Variations in light intensity within the microclimate can impact the tree's overall growth and its capacity to produce resin. Optimal light conditions are crucial for maintaining the health of Agarwood trees, as well as for promoting the growth of fungi and bacteria that aid in Agarwood formation.
- Wind: Wind patterns within the microclimate can influence the dispersal of fungal spores, affecting the likelihood of infection and Agarwood formation. Additionally, strong winds can cause physical damage to the tree, leading to injuries that may trigger the tree's defence mechanisms and the formation of Agarwood.
8. Seasonal changes
Seasonal variations have a substantial impact on the formation of agarwood, as they determine the Aquilaria tree's physiological functions, vulnerability to pathogens, and environmental interactions. The shifting environmental conditions throughout the year, including temperature changes, precipitation patterns, and moisture levels, can modify the tree's stress reactions, affecting agarwood resin production.
During times of heavy rain or high humidity, trees may become more prone to fungal invasions and other pathogens that can stimulate the creation of agarwood. On the other hand, in drier seasons, trees might undergo additional stress due to limited water access, which could contribute to resin formation as part of their innate defence system.
You may ask, what? So regardless of the dry or rainy season, Agarwood is formed regardless?
Correct, let me explain.
When it rains a lot or the air is very humid, trees are more likely to be attacked by fungi and other harmful organisms that can help create Agarwood.
However, when the weather is dry, trees might experience extra stress because there is insufficient water. This stress can cause the trees to produce resin as a natural way to protect themselves.
Additionally, temperature fluctuations across seasons can impact the activity levels of insects and microorganisms, such as wood-boring insects or endophytic fungi and bacteria, which play essential roles in initiating the process of agarwood formation. As temperatures rise, these organisms may become more active, resulting in increased mechanical damage and infection in Aquilaria trees, thus potentially encouraging agarwood development.
In conclusion, seasonal changes create a complex environment for Aquilaria trees, affecting their physiological responses, relationships with microbes and insects, and susceptibility to various stress factors, all of which can play a role in the formation and quality of agarwood.
9. Environmental changes
Similar to point 7 with an additional:
- Air quality and pollution: Changes in air quality, such as increased pollution levels, can negatively impact the overall health of the Aquilaria trees. Exposure to pollutants may weaken the trees, making them more susceptible to infections and injuries that can stimulate the formation of agarwood.
- Natural disasters and human disturbances: Environmental events like floods, storms, or fires, as well as human-induced disturbances like logging and land clearance, can cause physical damage to the trees. These injuries can make the trees more vulnerable to infections, leading to increased resin production and agarwood formation.
The above factors happen in the jungle or wild forest only. In plantation, we do not wish to create pollution. The air of our plantation and clean, and it is far away from the city and any other industrial factories. Also
10. Region where the tree comes from
Refer to the introduction.
The Aquilaria tree is native to the dense tropical forests of Southeast Asia, including countries such as Bangladesh, Nepal, India, Malaysia, Thailand, Cambodia, Southern China, Sri Lanka, Vietnam, the Philippines, and Indonesia. This region's warm and humid climate provides ideal conditions for the growth and development of the Aquilaria tree, which thrives under the canopy of these lush forests. These trees have long been valued for their ability to produce Agarwood, a rare and precious resinous wood used for centuries in traditional medicine and religious rituals and as a prized ingredient in perfumery. Refer to the introduction for more information.
11. Types of fungi and bacteria attacking the trees
This Aquilaria tree and some tiny fungi friends work together to make agarwood when the tree gets hurt. Scientists wanted to learn more about how these fungi help, so they studied two wounded trees and watched the fungi for a whole year.
They found out that lots of fungi come right after the tree gets hurt, but then fewer and fewer show up over time. The tree might be protecting itself by making some special chemicals to keep the fungi away. Each tree is a little different, so the story isn't the same for every one of them.
The captivating dance between wound, fungi, and the coveted agarwood unfolds. Despite its fascinating biological story, our understanding of Aquilaria's complex relationships with its diverse fungal partners remains shrouded in enigma. This groundbreaking study pulls back the veil, closely observing the shifting sands of three natural fungal colonisers in two wounded wild Aquilaria specimens over the course of a full year.
Harnessing the power of species-specific primers and the finesse of quantitative real-time PCR (qPCR), researchers unveiled the captivating dynamics of Cunninghamella Bainieri, Fusarium Solani, and Lasiodiplodia Theobromae, three species intimately connected with the formation of agarwood. To further unravel the intricate tapestry of time's impact on agarwood quantity and quality, 14 wood samples were meticulously gathered from different moments in the tree's post-wound life: from mere hours after injury to the changing of the seasons (Mohamed, R., Jong, P.L. & Nurul Irdayu, I (2014)
What the qPCR data exposed was nothing short of remarkable - a story of decline, with fungal populations surging in the immediate aftermath of wounding (40- to 25,000-fold increases), only to gradually ebb away over the months (<1- to 3,200-fold increases). This subtle choreography suggests the potential involvement of secondary metabolites in the tree's defence response, a natural attempt to keep fungal invaders at bay.
Yet, as in any great tale, no two narratives were the same. The succession patterns in the two trees differed, hinting that the delicate balance of fungal populations could be swayed by the unique environments and microclimates surrounding each individual tree's wound. The knowledge gained in this study sheds invaluable light on the enchanting world of wild Aquilaria species and their associations with wound-induced agarwood formation. It paves the way for a deeper understanding of the possible role fungi play as secondary catalysts in the intricate dance of agarwood production, particularly when humans intentionally wound these trees to coax forth their precious aromatic resin.
Various fungi and bacteria have been isolated from agarwood, including Aspergillus sp., Alternaria sp., Botryodyplodia sp., Cladosporium sp., Diplodia sp., Fusarium Bulbiferum, and others. Endophytic bacteria like Bacillus cereus, Burkholderia, Staphylococcus aureus, and Escherichia coli have also been found in Aquilaria trees.
12. Tree processes related to the immune system and defence mechanisms that produce essential oil
When Aquilaria trees are infected or inoculated, oleo-resin is produced to defend against pathogens. Secondary metabolites found in the wood, such as terpenoids, phenolics, lipid droplets, and alkaloids, are important in the plant's defence system. The volatile chemicals in agarwood oil, which are mostly terpenoid substances, are some of the most valuable compounds produced by plants.
13. Endophytes (organisms) living in the tree
Endophytes, including fungi and bacteria, live in all parts of Aquilaria trees and play a role in supporting healthy growth and the plant's defence system. Some chemical compounds found in agarwood are obtained from endophytic organisms, such as Bacillus, Pseudomonas, and Burkholderia bacteria, which produce a wide range of secondary metabolites. Please refer to point 11
14. Location within the tree where agarwood is formed or collected
Agarwood primarily forms in the trunk and branches of the Aquilaria tree as a result of injury, infection, or other forms of stress.
When an Aquilaria tree experiences an injury, whether from natural causes or human intervention, the tree's natural defence mechanisms are activated. This causes it to produce resinous compounds, which accumulate in the infected areas, resulting in the formation of agarwood. The location of these injuries or infections within the tree can influence the concentration, quality, and overall amount of agarwood produced.
For instance, if a particular area within the tree is more prone to infection or injury, it may lead to a higher concentration of agarwood in that specific location. Conversely, if the tree is healthy and undisturbed, the formation of agarwood may be limited or not present at all.
Moreover, the location within the tree can affect the ease of collecting agarwood. When the resinous wood is found deeper inside the trunk or in larger branches, it may require more invasive extraction methods, affecting the tree's overall health and future agarwood production. In contrast, when agarwood is located in more accessible areas, it can be harvested with minimal impact on the tree.
15. Length and intensity of light exposure in treated wood
Any trees need light to complete the photosynthesis process, to grow big and stay strong. The sunlight helps the tree make energy and stay healthy.
The amount of sunlight the tree gets daily and its brightness can change how much agarwood it forms.
Sometimes, when the tree gets lots of sunlight, it is better at fighting off things that could harm it, like insects and germs. This might mean it will not form as much agarwood.
But if the tree does not get enough sunlight, it might not be as strong and healthy. This can make it easier for germs and insects to hurt the tree. When the tree gets hurt, it tries to protect itself by making more agarwood.
Also, the number of hours the tree spends in the sun daily can change how fast it grows. More sunlight helps it grow quickly, while less sunlight makes it grow more slowly. When it grows slowly, the tree might use more of its energy to protect itself by making agarwood.
So, the sunlight that the tree gets can change how much agarwood it makes. By caring for the tree and giving it the right amount of sunlight, we can help it create more of the wonderful smelling agarwood.
16. Inoculation methods
Wounding followed by pathogen invasion or inoculation has been shown to be successful in agarwood formation. Researchers have found that xylem parenchyma cells and interxylary phloem turn starch granules into oleoresin, accumulating as droplets in these cells. The accumulation of oleoresin is followed by an aromatic odour, indicating the formation of agarwood.
Forestry experts have attempted artificial inoculation by inflicting deep cuts or bores in the trunks of young trees and directly injecting the fungus into the heartwood. This technique allows for oleoresin extraction from trees younger than 10 years, proving successful in some smaller agarwood species like A. Sinensis—extensive plantations of A. Sinensis are found in tropical regions of China, Vietnam, Thailand, Malaysia, Indonesia, and Cambodia.
Some highlights
- In 1929, Tunstall was the first to use a fungal-inoculation method to produce agarwood.
- Over the years, many different fungi and techniques have been tested to find the best way to induce agarwood formation.
- In 2005, the Cultivated Agarwood Kits (CA-Kits) were developed and proved successful.
- In 2010, the Whole-tree Agarwood-Inducing Technique (Agar-WIT) was patented for a more efficient agarwood production process.
- In recent years, several patents for fungal strains, chemical inducers, and new delivery methods have been granted.
Refer back to the abovementioned: “age of infection.”
Agarwood Collection:
In the past, people did not have full knowledge of this tree, they cut it cut down, scrapped some of the white wood away and buried it for a year until only its aromatic heartwood remained. The wood will be rotted and decomposed first, and the resin- Agarwood remains.
Currently, some Agarwood plantations, like ours, have a team to scrap away the whitewood. This is a very labours task.
That is for today, I hope you have learnt a bit about Agarwood today.
If you are interested, click the below link for the collection that interests you.
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