Agrostis trachychlaena (bentgrass)

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 (Image: Niek Gremmen)

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

Agrostis trachychlaena (Image: Niek Gremmen)

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.

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.

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Agrostis trachychlaena (Image: 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 on-line 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.

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.

GrassBase - Agrostis trachychlaena

Search Kew's databases for more information on this species

UK Overseas Territories team at Kew

The grass family (Poaceae)

Commelinids group at Kew

ARKive – Agrostis trachychlaena