It’s not the most spectacular looking plant, but when it comes to rarity the Triangular club rush is the UK’s botanical equivalent of the tiger. This unassuming sedge is disappearing fast with the last remaining specimens growing in just a few small clumps beside the River Tamar.
Concerned at the scale of the decline, scientists from the Environment Agency are making a final attempt to save the species with help from Kew Garden’s Millennium Seed Bank, Natural England, the National Trust and ecologist Peter Nicholson from Panscape Environmental Consultants.
On Thursday, June 10 staff from Kew and Wakehurst Place, the Millennium Seed Bank nursery where the plants were grown, will travel down to the River Tamar to deliver the latest batch of Triangular Club Rush to the new nursery at Cotehele. Joining Environment Agency officers on the day will be representatives from Natural England and the National Trust who have supported and helped fund the project.
The reason the plant is so close to extinction is not known. Scientists believe it might be due to increased competition from fast-growing reeds or changes in riverbank management. Alternatively, it might be due to stormier weather conditions or increased competition from alien waterside plants.
The UK is the most northerly extent of the Triangular club rush’s range. Habitat loss has already seen it disappear from places such as the Thames and Medway. Restricted to the upper reaches of tidal estuaries, the plant has a bright green angled stem and can grow from 50-150 cm in height. It flowers in August and September.
A survey of the River Tamar in 2009 revealed the rare sedge is now only found in four distinct clumps near Calstock. The total area covered by these few surviving plants is less than four square metres.
The National Trust has given permission for a nursery area to be created at Cotehele where Triangular club rush plants will be specially grown for re-planting at other suitable locations in the estuary. The nursery, at Morden stream, was chosen because it has a suitable habitat offering bank stability, an open aspect and low salinity. The nursery will be managed by National Trust staff from Cotehele.
This latest rescue attempt builds on an earlier project in the 1990’s when a number of plants were removed from the Tamar and cultivated by Kew Gardens. Propagated plants from Kew were then planted at selected sites on the estuary in 1997/1998 in a bid to boost a small population of native Triangular club rush around Rumleigh Quay. This work effectively saved the plant from extinction.
Further research and monitoring by the Environment Agency has increased scientists’ understanding of the ecology and habitat requirements of the rare sedge and they are now more confident of the plant’s chances of survival.
“The decline of the Triangular Club Rush is causing serious concern. This is our last chance to save this critically endangered species,” said Jess Thomasson for the Environment Agency.
“After careful research we have identified a handful of sites where re-introduced plants will have the best chance of survival. Also, having a reservoir of Triangular Club Rush plants at Cothele will greatly increase the likelihood of success by allowing further planting in historic strongholds on the Tamar.”
(image: Triangular club-rush, Tamar Estuary by Peter Wakely © English Nature)