Aquilaria crassna

Aquilaria crassna, or agarwood, is an evergreen tree. It belongs to the Thymelaeaceae family. It comes from Thailand, Cambodia and Vietnam in Southeast Asia. It grows in both old forests and regrown woodland. Trees grow on shallow, rocky soils, often near streams. They reach sites up to 3,281 feet [1,000 metres] above sea level. People also grow it near homes, gardens and temples.

The tree has an open crown. It keeps its leaves all year. Its usual height is 49–66 feet [15–20 metres]. Rare trees reach 98 feet [30 metres]. Plants For A Future gives a spread of 49 feet [15 metres]. The trunk measures about 1.3–2 feet [0.4–0.6 metres] across. Some trunks reach 3.3 feet [1 metre] across. Bark yields fibre for cloth, hammocks and paper pulp. People use the wood for furniture and posts. It also serves as fuel and makes charcoal.

This tree needs the warmth and moisture of the tropics. It grows best with daytime temperatures of 22–28°C. Plants For A Future lists USDA zones 10–12. Young trees grow well with some shade. Larger trees need more light. Sun suits trees that have settled into their growing site. It prefers moist ground and accepts sand, loam or clay. It can grow in poor soil, including very acidic ground. Slightly acidic and neutral soils also suit it.

The tree yields scented resin for incense and perfume. Burning agarwood has a long role in religious rites. Its incense also helps repel insects. Trials in Cambodia found it could grow beneath mixed tree crowns. Growers raise it from seed or root cuttings. They also use air layers. Fresh seed needs prompt sowing. Within ten weeks, it loses its power to sprout. Seeds can start to sprout within ten days. This can go on for a month. Rooting hormones help with cuttings and air layers.

Taking wood rich in resin has put wild trees under severe pressure. Useful Tropical Plants cites the 2011 IUCN assessment. It reports the tree's status as critically endangered. It links large losses in Vietnam to the perfume trade. Plants For A Future records no known edible uses. Both reference sources report no known hazards. This does not mean the tree is safe. Traditional medicine uses the root, wood and resin. Uses include stomach problems, asthma and nerve disorders. These records describe traditional practice. They do not prove that these treatments work.