English Name : Eagle Wood, Lignum Aloes, Oud, Aloe Wood, Calambac, Aglia Akyaw.
Scientific Name : Aquilaria Crassana Pierse
Family : Thymelaeaceae
Genus : Aquilaria

The word “Aquilaria” means eagle in Latin and means black or dark in Acadian. There are altogether 25 species in its family, amongst all these, only 4 species are found in Thailand:
1. Aquilaria Malaccensis
2. Aquilaria Crassna
3. Aquilaria Subintegra
4. Aquilaria Hirta

Aquilaria Malaccensis
Local Name : Mai Hom
Tree can grow up to 20m tall. The depletion of wild trees from indiscriminate cutting for Oud has resulted in the trees being listed and protected as an endangered species. Projects are currently underway to produce Oud in a sustainable manner.

Aquilaria Crassna
Local Name : Krissana
Descriptions: Aquilaria crassna is a timber species with a thin crown and straight stems. It usually reaches from 15-20 m high, but it can grow up to 30-40 m , and produce boles from 40-50 cm in dbh. Chan krassna is a light-demanding species that can regenerate under a forest canopy of 0.4 – 0.6 shading. The tree normally grows from 300-800 m a.s.l on deep sandy clay soils, but some individuals have been discovered at 2000 m a.s.l. The tree occasionally produces a valuable resin called "Chankrosna" in its stem. Although this resin occurs naturally in only a small percentage of trees in the Thymeleaceae family, the quality resins are harvested from a several species of Aquilaria.

Aquilaria Subintegra
Local Name : Gaharu
Descriptions: A. malaccensis or commonly known as Gaharu is the most widespread than any other Aquilaria species. It is a large, evergreen tree growing up to 40 m tall and with diameter greater than 60 cm. The bole is often straight, smooth bark, pale whitish and stripping off in long fibrous pieces. Inner bark is white or cream with soft sapwood and wood with included phloem.

Aquilaria Hirta
Local Name : Janae
Descriptions: Aquilaria Hirta is an evergreen tree of around 14 meter high. Its leaves are hairy, pointed, 6.5-14 cm. long, and 2.5-5.5 cm wide. Its white or light yellow blossoms bloom in March. Its fruits is pointed like a spearhead. It is generally found on the plain e.g. in Narathivas, Thailand