Agarwood refers to very dense, dark, resin-enriched heartwood that is derived from various species of the genus Aquilaria (Thymelaceae). It is extremely valuable and is used as a source of incense and medicine, as well as for carving.
“The Port for Shipping Fragrance”
Hong Kong has had a close relationship with agarwood throughout the city’s history.
As early as the Ming Dynasty, the area around Dongguan in Guangdong Province was known for its abundant agarwood. Sun Yat-sen’s home county, Zhongshan, was originally named “Xiangshan” (“fragrant mountain”) because of the agarwood that grew there. Xiangshan was originally part of the Dongguan region; however, it was renamed Zhongshan County to honor Mr. Sun Yat-sen in 1925.
In its early years, Hong Kong was the main port for shipping the aromatic woods from the Dongguan region overseas, including agarwood. Over time, the port became known as “Xiang Gang”, which means “fragrant harbor” in Chinese (the name “Hong Kong” is based on its Cantonese pronunciation, “Heung Gong”).
In 1997, to commemorate the return of Hong Kong, 1997 agarwood trees were planted in the Xianhu Botanical Garden in Shenzhen. On a hill in the botanical garden, the agarwood trees are shaped like a map of China, illustrating the close connection between Hong Kong and China, as well as Hong Kong and traditional Chinese medicine.
The author standing in the Xianhu Botanical Garden in Shenzhen, with the 1997 agarwood trees planted in the shape of China on the adjacent hillside
Priced Like Gold
There is a street in Hong Kong called Ko Shing Street (also called the “Herbal Medicine Street”), where many valuable medicinal herbs are sold. I often brought students to visit and study there. Each time we visited a unique old shop, where the owner would allow the students to see rare specimens of agarwood. The shop had a 700-gram piece of top-quality agarwood that was valued at 8 million RMB (1.2 million USD).
Mr. Chun-hung Lee and the author in his shop, holding one of the most valuable pieces of agarwood in the world. (Provided by Mr. Chun-hung Lee)
Agarwood is extremely expensive because it is very scarce. Not every agarwood tree produces resinous agarwood; in fact, its formation comes from a pathological process.
The aroma of agarwood is derived from its resin; healthy agarwood trees do not secrete resin. When the tree is injured—for example, when it is struck by lightning or attacked by insects– the wound becomes infected by fungi and the trees secrete resin. It is commonly said that agarwood comes from “sick trees”; in nature, it can only be found by chance. Similarly, not every cow produces bezoars and not every oyster produces pearls.
The author of the text Ben Cao Yan Yi, Kou Zongshi, lived in the Song Dynasty (960-1279) and once worked in the Song Dynasty Medical Bureau; he was responsible for managing the herbal market and identifying medicinal materials. His position was akin to a modern-day director of a national drug testing center. Kou Zongshi had extensive knowledge and rich experience in the identification of medicinal materials. In his book, he noted that: “some agarwood trees are so large that several people can wrap around a single tree… However, among a hundred agarwood trees, it is hard to find even one or two trees that contain agarwood resin.”
Agarwood Uses
Agarwood is used as a material for making high-quality incense. It is used in incense not only in China, but also in Japan, Korea, and Vietnam. Agarwood has a long history of incense use in Buddhism, Zen practices, and meditation. Yu Deling, a female official in the late Qing Dynasty, documented in the “Royal Records of Incense” (Yu Xiang Piao Miao Lu) that the Empress Dowager Cixi loved to use agarwood. She reported that there were many incense burners in the palace, and the smoke never ceased, purifying the body and mind.
Another application of agarwood is in medicine. Its medicinal use was first mentioned in the text Ming Yi Bie Lu(Miscellaneous Records of Famous Physicians), which was written during the Southern and Northern Dynasties period (420-589); it was classified as a “superior” medicinal. The Ben Cao Gang Mu (Compendium of Materia Medica) describes about a dozen formulas containing agarwood, of which seven were newly added by Li Shizhen.
Agarwood is acrid, bitter, and slightly warm in nature. It moves qi to relieve pain, warms the stomach and stops vomiting, and grasps qi to calm panting. It is an ingredient in classic formulas such as Zi Xue Dan, Si Mo Tang, and Su He Xiang Wan. Modern research shows that agarwood has calming, pain-relieving, and antibacterial properties.
The third major use of agarwood is as a raw material for carving and art. I had the opportunity to see a cup carved from agarwood at an art exhibition that looked just like a cup carved from rhino horn. Many agarwood accessories were stored in the Imperial Palace, and carved agarwood bracelets are valuable collectors’ items. Over the years, I have collected agarwood bracelets of various grades and origins, and I have enjoyed them for years.
Agarwood naturally features fine grains and possesses a smooth texture and profound fragrance, and does not require carving. Thus, herbal stores and antique shops often display treasured pieces of agarwood in their windows.
Resource Distribution
Agarwood comes from several species of trees in the Thymelaeaceae family, which are mainly distributed in tropical and subtropical regions.
In China, domestic agarwood is derived from Aquilaria sinensis (Lour.) Gilg. This species is the only plant source specified by the Chinese Pharmacopoeia (2020 edition) for use in medicine. It is primarily produced in Guangdong, Guangxi, Hainan and Fujian Provinces.
Fruiting branch of Aquilaria sinensis (Lour.) Gilg
While the propagation of agarwood trees is not difficult, the challenge lies in coaxing them to naturally produce resin.
To increase the number of trees that produce agarwood resin, previous generations created methods to stimulate the production of resin. During the Republican period (1912-1949), the “Dongguan County Chronicle” recorded one method to encourage the trees to produce resin. The trees were first cut to form an injured area, which promotes the formation of resin. This technique was called “opening the resin door”, and it is still in use today.
Agarwood that fails to form resin cannot be used as medicine. It is considered to be “agarwood wood that lacks resin”.
The process of producing resin takes 10 to 20 years. Although large areas have been devoted to cultivating agarwood in Hainan province, it will take time for the trees to produce resin. Thus, a quick route to success remains elusive in the agarwood industry.
Agarwood imported into China is derived from Aquilaria agallocha Roxb., which is another species from the same genus. It is primarily produced in Indonesia and Malaysia, as well as Myanmar, Thailand, Vietnam, Laos, and Cambodia.
Today, wild agarwood trees are rare in China. In Vietnam, high quality agarwood production is also limited, and the trees are on the verge of extinction. At present, all wild species that produce agarwood are protected by the Convention on International Trade in Endangered Species (CITES).
Authenticity
There are four key characteristics to distinguish authentic agarwood. The first is density. High quality agarwood resin is very dense; its Chinese name means “sinking fragrance”, because it sinks in water. As early as the Ben Cao Gang Mu (Compendium of Materia Medica), Li Shizhen noted: “the heartwood sinks when placed in water; thus, its alternate names include “sinks in water” (Chen Shui) or “water sinking” (Shui Chen).” Unfortunately, in the modern market there are ways to artificially increase its weight, so the test of “sinking in water” cannot be used alone to assess quality.
High-quality agarwood has a subtle aroma that is very enduring. If it has an acrid smell that irritates the nose, it has likely been adulterated with aromatic compounds or other chemicals.
When held in the hand, the texture of high-quality agarwood should not be sticky; this texture was traditionally described as “not losing oil” when touched. If there is a residue from oil remaining on the hands, it is likely adulterated.
When agarwood is burned, it should emit a strong aroma and exude brown resin, with white-colored smoke. High quality agarwood will slowly release different aromas at different temperatures and different stages of combustion. Just like a cup of tea, it tastes different when steeped in different water temperatures and for different times.
In addition to the above-mentioned empirical identification methods, test methods using analytical instruments and microscopy are also effective to evaluate quality. I have conducted microscopic identification research on agarwood, and studied its microscopic characteristics such as its columnar calcium oxalate crystals. The “oil lines” visible in of agarwood are fibrous tracheids, vessels, resinous clumps, and parenchyma cells containing yellow-brown secretions. My research results, with photographs, have been included in The Pharmacopoeia of the People’s Republic of China – Color Atlas of Microscopic Identification of Traditional Chinese Medicine Powder.
Microscopic characteristics of agarwood
In the 1970s in Quanzhou, Fujian Province, cultural relics were salvaged from an ancient shipwreck of the Song Dynasty (700 years ago). The ancient ship was 24 meters long and nine meters wide; it had a very graceful shape and was a medium-sized ship in its era. Porcelain, silk, spices and fragrant materials, such as agarwood, sandalwood, pepper and frankincense were discovered in its hull. Today, this ancient ship is quietly displayed in a museum, a witness to history. It tells its visitors a tale of the Maritime Silk Road and the journey of aromatics across thousands of miles.
