• Species: Eusideroxylon zwageri Teijs. & Binn.
  • Synonim: –
  • Commone name: Borneo Ironwood
  • Vernacular name: Ulin, Belian
  • Conservation Status: Vulnerable (VU A1cd+2cd ver 2.3 IUCN 1998)
  • Distribution: Borneo (across island), Southern part of Sumatra, and Bangka-Belitung

Borneo Ironwood (Eusideroxylon zwageri), or wellknown as Ulin, is a native trees to Indonesia, especially on the islands of Sumatra and Kalimantan. This evergreen tree can grow up to 40 meters with a stem diameter reaching 150 cm. The leaves are arranged alternately. The lower leaf surface with a fine hairs, an overall is light- to green, but reddish in young leaves. The inflorescens is compound stretches along 10-20 cm. The fruit is Drupe which 7-16 cm in size, single seeded and large in size. Ironwood grows in lowland primary forests with an altitude of up to 500 meters above sea level. This plant can grow in sandy clay soils, acidic pH, and low levels of macro nutrients.

The Borneo ironwood population has decreased in its natural habitat. This population decline is caused by over-exploitation and conversion of forests that become natural habitats into agricultural land, plantations, or residential areas. In Sabah and Kalimantan they still export this wood. In Sumatra, there was a lot of illegal timber exploitation of this species to be used as building materials due to a lack of supervision from local authorities. In addition, the species has a long time regeneration cycle.


Asian Regional Workshop (Conservation & Sustainable Management of Trees, Viet Nam, August 1996). 1998. Eusideroxylon zwageri. The IUCN Red List of Threatened Species 1998: e.T31316A9624725. http://dx.doi.org/10.2305/IUCN.UK.1998.RLTS.T31316A9624725.en. Downloaded on 01 March 2019.