Zhongzhen Zhao Li Liang Eric Brand
Abstract: Agarwood refers to the 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 fragrance, as medicine, and for carving.
Fragrant Harbor
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 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 overseas shipment of Dongguan’s fragrant materials, including agarwood. Over time, the name of the port became “Xiang Gang” which means “Fragrant Harbor” in Chinese, and which is pronounced “Heung Gong” in Cantonese. Thus, agarwood commerce is the source of Hong Kong’s name.
In 1997, to commemorate the return of Hong Kong to the motherland, 1997 agarwood trees were planted in Xianhu Botanical Garden in Shenzhen. On a hill in the botanical garden, the trees form the shape of a map of China, showing that Hong Kong and China, and that Hong Kong and traditional Chinese medicine, are closely related.
I am standing in Xianhu Botanical Garden in Shenzhen. The 1997 agarwood trees planted in the shape of the map of China are on the hillside behind me
Price Comparable to Gold
There is a unique street in Hong Kong called Ko Shing Street (also called “Herbal Medicine Street”), where many precious medicinal herbs are sold. When I was teaching, I often took students there to visit and study. Every time I went, I visited an old shop whose owner Mr. Chun-hung Lee would take out precious agarwood for our students to see. The elderly shopkeeper had a 700-gram piece of top-quality agarwood, valued at 8 million RMB (1.2 million USD).
Agarwood is so expensive mainly because it is so scarce. Not every agarwood tree produces agarwood; in fact, the formation of agarwood is a disease process.
The fragrance of agarwood comes from resin; healthy agarwood trees do not secrete resin. Only when the tree is injured—for example, when it is struck by lightning or attacked by insects—and the wound becomes infected by fungi do the trees secrete resin. In fact, “agarwood resin” in Chinese means “sick and healed wood”, Thus, in nature, agarwood can be found only by chance. Just as not every cow generates bezoar, and not every clamshell has pearls inside, only one out of a hundred agarwood trees has resin inside.
Kou Zongshi, author of Ben Cao Yan Yi in the Song Dynasty (960-1279), once worked in the Huimin Bureau of the Song Dynasty, where he was especially responsible for managing the medicinal material market, including identifying medicinal materials. In other words, he was roughly equivalent to the director of the current Food and Drug Administration. Kou Zongshi had extensive knowledge and rich experience in the identification of medicinal materials. In this book he records: “Some agarwood trees are so big that they require several people to hold a single one …But, among a hundred agarwood trees, it is hard to find one or two trees with agarwood resin.” The fact that this would be mentioned in such an old book shows how valuable and scarce this unusual material was, even at that time.
Agarwood Uses
One of the uses of agarwood is as a source of fragrance. In particular, it is an important raw material for incense products not only in China, but also in Japan, Korea, and Vietnam. China has a long history of using incense. Incense is burned to worship the Buddha and during meditation, as well as simply to scent the air. Yu Deling, a female official in the late Qing Dynasty, wrote in the “Royal Fragrance Ethereal Document (Yu Xiang Piao Miao Lu)” that the Empress Dowager Cixi loved to use agarwood. She reports, “There are many incense burners in the palace, and the smoke lingers.” It was, and is, believed that inhaling incense can purify the body and mind. This may be because certain components of agarwood resin can act on the central nervous system and calm the nerves.
The second use of agarwood is as medicine. This use of agarwood was first mentioned in the Ming Yi Bie Lu of the Southern and Northern Dynasties (420-589). This book lists agarwood as an “upper-rank” medicine. The Compendium of Materia Medica contains a dozen or so formulas containing agarwood, of which seven were newly added by Li Shizhen.
Agarwood is pungent, bitter, and slightly warm in nature. It has the effect of relieving pain by activating Qi, relieving vomiting, and relieving asthma. The classic proprietary Chinese medicines Zi Xue Dan, Si Mo Tang, and Su He Xiang Wan all contain agarwood. Modern research shows that agarwood has sedative, analgesic and antibacterial pharmacological activities.
The third use of agarwood is as a raw material for carving and handicrafts. I once saw a rhino horn-shaped cup made of agarwood in an exhibition, and it looked exactly like a real rhino horn cup. There are also many agarwood toys collected in the palace. Today, probably the most common form of carved agarwood is as beads which are strung together as bracelets. Such bracelets are used in meditation and/or collected. Over the years, I have collected agarwood bracelets of different origins and grades, and I keep them as precious treasures.
Agarwood is beautiful in its natural form. It has a smooth, even silky surface texture and subtle fragrance, with no need for carving. Thus, today, medicinal material stores and antique shops display agarwood in their front windows as a treasure.
Resource Distribution
Agarwood comes from several species of trees in the Thymelaeaceae family, mainly distributed in tropical and subtropical regions.
In China, domestic agarwood is derived from Aquilaria sinensis (Lour.) Gilg. This species is the only legal original plant source for its use as a medicine, according to the Chinese Pharmacopoeia (2020 edition). It mainly grows in Guangdong, Guangxi, Hainan and Fujian Provinces, and it has been planted on a large scale in Hainan.
The reproduction and growth of agarwood trees themselves is not difficult; the difficulty is in coaxing them to produce resin.
To increase the number of trees that produce agarwood resin, the ancestors invented artificial methods. In the period of the Republic of China (1912-1949), “Dongguan County Chronicle” recorded one artificial method that was used to encourage trees to produce resin. The trees were first cut to form an injured area to promote the formation of resin. This procedure 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 belongs to the category of “agarwood without resin”.
After “the resin door” is successfully opened, producing resin takes 10 to 20 years. Speeding up this process is impossible, as far as we know now.
Agarwood imported into China is derived from Aquilaria agallocha Roxb, another species of the same genus as the Chinese tree. The wood of this species is produced in Indonesia, Malaysia, Myanmar, Thailand, Vietnam, Laos, Cambodia and Bangladesh.
Nowadays, wild agarwood trees can hardly be found in China. In Vietnam, wild agarwood trees are also scarce, and the species is on the verge of extinction. At present, all wild species that produce agarwood are listed in, and protected by, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Authenticity
There are four characteristics you can use to distinguish authentic from fake agarwood. One is its density. High-quality agarwood resin is very dense, with a large specific gravity. This means it sinks in water. As early as in the Compendium of Materia Medica, Li Shizhen mentioned: “The heartwood will sink when placed in water; hence it is called sinking in water (Chen Shui), also known as water sinking (Shui Chen).” Unfortunately, now there are cases of unscrupulous dealers artificially increasing the weight with foreign matter and compression, so “sinking in water” should not be the only way to assess the quality of a piece of supposed agarwood.
The second characteristic is its fragrance. True agarwood has a subtle, distinctive, ethereal fragrance that is very long-lasting. If a piece of supposed agarwood has a pungent smell, it has been tainted with additional spices or other chemicals. Texture is the third characteristic you can use to judge authenticity. High-quality agarwood should feel smooth, but not greasy. The ancients described this as no oil-releasing (Zou You) when touched. If there are oil marks left on your hands after touching it and the oil looks like a moisturizer, then the agarwood is probably fake.
Burning gives yet another clue. After agarwood is ignited, there should be a strong aroma, accompanied by the exudation of brown resin and emission of white smoke. High quality agarwood will slowly release different aromas at different temperatures and different stages of combustion. It’s just like a cup of tea, where different water temperatures and different brewing times give different tastes.
In addition to the above-mentioned empirical identification methods, test methods using analytical instruments and microscopes are also effective ways to evaluate the 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.
In Quanzhou, Fujian Province, there are cultural relics salvaged in the 1970s from an ancient shipwreck of the Song Dynasty (700 years ago). The ancient ship was 24m long and 9m wide. It was very beautiful in shape and was considered to be a medium-sized ship at that time. In the hull were found porcelain, silk, spices and fragrant materials, such as agarwood, sandalwood, and frankincense. Today, this ancient ship is quietly displayed in a museum, silent witness to history and testament to the enduring allure of agarwood.
Author information:
Dr, Zhao Zhongzhen， Former deputy dean and professor of the School of Chinese Medicine of Hong Kong Baptist University, distinguished professor of Beijing University of Chinese Medicine, and founding director of the Compendium of Materia Medica Research Institute.
Dr. Li Liang Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong.
Dr. Eric Brand Hong Kong Baptist University, 7 Baptist University Road, Kowloon Tong, Hong Kong.
