Skip to main content
You are here
Facebook icon
Pinterest icon
Twitter icon

Agrostis trachychlaena (bentgrass)

A rare grass species, Agrostis trachychlaena occurs within an area of only 16 km² on two islands in the South Atlantic Ocean. Fewer than 250 mature individuals are thought to survive.
Agrostis trachychlaena (bent grass)

Agrostis trachychlaena (Photo: Niek Gremmen)

Species information

Scientific name: 

Agrostis trachychlaena C.E. Hubb.

Common name: 

bentgrass (although this name is also applied to other species within this genus)

Conservation status: 

Endangered (EN) according to IUCN Red List criteria.


Rocky slopes, open patches in Spartina arundinacea tussock, and around albatross nesting sites.

Key Uses: 

None known.

Known hazards: 

None known.


Genus: Agrostis

About this species

Agrostis trachychlaena is a rare species of grass that grows in loose clumps on rocky slopes on two islands in the South Atlantic Ocean. Specimens of A. trachychlaena were first brought back from Inaccessible and Nightingale Islands by botanist Erling Christophersen, as part of the Norwegian Scientific Expedition in 1938. Specimens from Nightingale Island were collected by scientist Nigel M. Wace on his visits in 1968 and 1976. The most recent collections were made by Peter Ryan in 2007.


Discover more

Geography and distribution

Agrostis trachychlaena is restricted to Inaccessible Island and Nightingale Island in the South Atlantic Ocean. These islands are part of the Tristan da Cunha group, which is located 2,400 km south of St Helena (the UK Overseas Territory of which Tristan da Cunha is a dependency).

Agrostis trachychlaena (Photo: Niek Gremmen)


Overview: A short, perennial herb growing in loose clumps, with culms (stems) of 20-55 cm long.

Leaves: The ligule (appendage between the leaf sheaf and blade) is papery, 1-3 mm long and irregularly lobed. The leaves are 2-7 cm long and 0.5-2 mm wide. The leaf surface is ribbed and the leaves taper to an acute point at the end.

Flowers: The inflorescence is a tight panicle, 1.5-5.5 cm long and 0.6-1.6 cm wide. The spikelets (clusters of flowers) are 3-4 mm long and are solitary, the fertile ones having pedicels (stalks) 0.3-2 mm long.

Threats and conservation

It is estimated that fewer than 250 mature individuals of Agrostis trachychlaena exist in the wild, and these are spread over a small area (less than 16 km²), adding to their vulnerability.

It is not known why this species is so rare, although it is thought unlikely to be the result of human activity; erosion of these volcanic islands and subsequent loss of habitat could have played a part. Fire is a potential threat, and a Spartina arundinacea tussock can be easily lit and then burn for a long period.

Visitors to Nightingale Island could introduce alien species, which might pose a further threat, and hence advice on biosecurity is provided to all visitors.

Inaccessible Island is a designated Nature Reserve, out-of-bounds to tourists, as a measure to protect all of its wildlife, including A. trachychlaena.

Conservation assessments carried out at Kew

Agrostis trachychlaena is being monitored as part of the 'IUCN Sampled Red List Index for Plants', which aims to produce conservation assessments for a representative sample of the world’s plant species. This information will then be used to monitor trends in extinction risk and help focus conservation efforts where they are needed most.


Partnerships for conservation

Agrostis trachychlaena (Photo: Niek Gremmen)

Kew’s UK Overseas Territories (UKOTs) Programme works in collaboration with the Government of Tristan da Cunha Department of Conservation, together with international colleagues from the Netherlands and South Africa. 

Fieldwork supported by funds from the European Union and the Overseas Territories Environment Programme (OTEP) enables new herbarium specimens to be collected, including those of Agrostis trachychlaena.

Kew’s UKOTs programme is working with partners to produce a Tristan online herbarium. A seed-collecting programme has been started and the species collected are stored in Kew’s Millennium Seed Bank. A new annotated checklist for the Tristan group is being produced, which includes both native and introduced species.

This species at Kew

The only known dried specimen of Agrostis trachychlaena from Inaccessible Island, was collected by botanist Erling Christophersen, and is housed in the Herbarium at Kew. This is also the type specimen for the species.

Kew also holds specimens of A. trachychlaena collected on Nightingale Island by scientists Nigel M. Wace in the 1970s and Peter Ryan in 2007.

References and credits

Clayton, W.D., Harman, K.T. & Williamson, H. (2006 onwards). GrassBase - The Online World Grass Flora. (Accessed 10 August 2010). Available online.

Groves, E.W. (1981). Vascular plant collections from the Tristan da Cunha group of islands. Bull. Brit. Mus. (Na. Hist.) 8: 333-420.

Jakubowsky, G. (2003). Agrostis trachychlaena. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2. <>. Downloaded on 11 August 2010.

Kew Science Editor: Heather Lindon
Kew contributors: Colin Clubbe, Martin Hamilton
Copyediting: Emma Tredwell
Kew would like to thank the following contributors: Niek Gremmen (Data Analyse Ecologie, Diever, Netherlands)

While every effort has been taken to ensure that the information contained in these pages is reliable and complete, the notes on hazards, edibility and suchlike included here are recorded information and do not constitute recommendations. No responsibility will be taken for readers’ own actions.

Full website terms and conditions

Related Links

Courses at Kew

Kew offers a variety of specialist training courses in horticulture, conservation and plant science.

Students learn about plant taxonomy and identification

Why People Need Plants

A compelling book from Kew Publishing that explores the crucial role that plants play in the everyday lives of all of us.

image of book cover