Botanically, the tropical evergreen species of agarwood belongs to the genus Aquilaria and family Thymelaceae. Agarwood perfume can be extracted from eight species belonging to this genus. The four principal species are Aquilaria sinensis, Aquilaria malaccensis, Aquilaria agallocha, and Aquilaria crassna. Agarwood, or aloeswood, is often confused with aloe vera, which is a purgative. However, aloe vera has no fragrance, which likely eliminates it as a source of agarwood. The following verse perhaps led to this confusion: “How beautiful are your tents, Jacob, your dwelling places, Israel! Like valleys they spread out, like gardens beside a river, like aloes planted by the Lord, like cedars beside the waters” (Numbers 24:5–6). This verse suggests that aloes was local to Israel, but A. malaccensis and other aloes-yielding plants are native to southern Asia.
Aquilaria sinensis is the smallest of the four species, at just 5–15 meters in height. A. malaccensis and A. agallocha can grow to a height of 15 to 40 meters. The flowers of the tree emanate fragrance at night only. A. malaccensis and A. agallocha are found in eastern India, Bangladesh, and Myanmar. Other species extend across southeastern Asia in Malaysia, Indonesia, Thailand, Cambodia, Vietnam, and the Philippines.
Trees older than 60 years are best for extracting resin. Dark wood without white streaks indicates the presence of resin, which is produced when the heartwood is infected by a fungus. These fungi include Aspergillus spp., Botryodyplodia spp., Diplodia spp., Fusarium spp, Penicillium spp., and Pythium spp. (Anon., 1998a; Santoso, 1996, cited in Soehartono and Mardiastuti, 1997; Wiriadinata, 1995). As the wood rots, it produces a resin. This process can take centuries, making agarwood resin a scarce resource. Furthermore, in nature, only seven percent of the trees are infected by the fungi. Thus, the use of agarwood as timber is limited. However, extraction of resin requires the tree to be logged.
.High demand for the resin has led to overexploitation. The tree is not conducive to agroforestry cultivation either, as slow growth and low infection rates have reduced the return of investment substantially. The International Union for Conservation of Nature classified it as vulnerable, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora placed it in Appendix II. Appendix II species trade is constrained to protect their numbers to be so depleted that they are likely to go extinct. Additionally, India and Bhutan have restricted extraction to dead and fallen trees only. This international regulation has helped control demand and protect these trees for future generations, though the oleoresin that is locally produced from these forests is more likely to be illegally procured.
With just seven percent of the tree crop infected with the necessary fungi, forestry experts have tried to inoculate the fungus artificially by inflicting deep blazes (cuts) or bores in the trunks of young trees and injecting the fungus directly into the heartwood. With this method, oleoresin can be extracted from the stem and branches of trees that are younger than 10 years old. This method has been successful in some of the smaller agarwood species, like A. sinensis. Extensive plantations of A. sinensis exist in tropical regions of China, such as Hainan, Guangdong, and Hunan, as well as Vietnam, Thailand, Malaysia, Indonesia, and Cambodia. However the quality of oleoresin from these plantations is not as good as that found in nature. This further explains the huge price variations in the market.
In ancient times, agarwood was popular in Rome, Greece, Arabia, Persia, Egypt, India, and China. It was used in embalming (e.g., John 19:39–40), and such use continues in some Middle Eastern areas, such as Yemen. Historical records show that A. sinensis trees grew abundantly in Dongguan City (now Guangdong Province, China) about 400 years ago. Paper was made from its bark and used in eastern India and in China. The incense remains popular in many regions today, where it is used in pharmaceutical, personal care, and household products.
Like cinnamon, pepper, and other spices, aloes was imported from India in a vibrant trade that dates back to at least 3000 BC. Pure agarwood is heavy and sinks in water, and literature shows that the Chinese imported cb’enhsiang (the incense that sinks) from Vietnam during the Han Dynasty (200 BC–220 AD). Ancient medical Sanskrit texts refers to anarya, indicating that the tree was found in areas not inhabited by the Aryan people. (The Aryans often referred to local indigenous people living in the regions they occupied as anarya, which was also a derogatory term used to describe people who did not follow the cultural codes of the ruling Aryan people).
Agarwood or aloeswood was probably imported from the eastern tribal regions of India into the Indo-Gangetic plains, where the Aryan population was concentrated. Hoards of aloeswood, muslin, and pepper were recovered when the Byzantine King Heraclius (611–641 AD) sacked the imperial residence of the King of Persia. Arabic and Persian writings from 1100 AD and later contain multiple references to it. The cuneiform tablets from the Mesopotamian region also reference aloeswood.
Ancient Islamic texts contain numerous references to agarwood, or oudh. Archaeological evidence reveals that oudh was exported from India and Indonesia, largely in the form of oil and wood products. The Hadiths describe it as a treatment for throat-related ailments, as in the following text:
Umm Qais, daughter of Mihsan, the sister of ‘Ukasha b. Mihsan said: I visited Allah’s Messenger along with my son who had not, by that time, been weaned and he urinated over his (clothes). He ordered water to be brought and sprinkled (it) over them. She (further) said: I visited him (Allah’s Apostle) along with my son and I had squeezed the swelling in the uvula, whereupon he said: Why do you afflict your children by compressing like this? Use this Indian aloeswood, for it contains seven types of remedies, one among them being a remedy for pleurisy. It is applied through the nose for a swelling of the uvula and poured into the side of the mouth for pleurisy. (Book 26 of Sahih Muslim, #5487)