Apium repens, Creeping Marshwort

What is it?

This insignificant little umbellifer is one of Oxfordshire's rarest plants. For a long time its only UK locality was on Port Meadow at Oxford and it is endangered in Europe. Attention was drawn to it after the Rio convention in 1992 and we have been monitoring its up and downs on this open access site ever since. Flooding is part of its natural cycle, but summer flooding can bring population crashes There has been successful introduction to one new site and it has returned following suitable management to another in Oxford and one in Essex. Its future depends on partnership, with Natural England, the Environment Agency and Oxford City Council playing leading roles.

Does it grow anywhere else?

Creeping marshwort is known in the Atlas Mountains of Morocco and in the Canaries. In Europe it is widely scattered but never common, being found in the Czech Republic, Italy, Spain, France, Belgium and Holland. It grows in a wide range habitats from mown graves in Austria, river-side gravel banks in Slovenia, under water in Italy, to slightly saline pasture and dune slacks in Holland. Creeping marshwort has always been rare in England and Scotland with sites in Essex, Norfolk, Yorkshire, Fife and Argyle. During the 1960s it was only known at three localities in Oxfordshire, but by the 1970s only one site in the whole country.

The Oxfordshire Sites

Witney

The West Oxfordshire site at Witney had been subjected to improved drainage and treated with herbicide, leaving a species-poor, grassy field. The Environment Agency dug a scrape designed to enable buried seed to germinate in damp conditions, but although a number of other interesting species appeared there is still no creeping marshwort.

Binsey

The common land at Binsey, just across the river Thames from Port Meadow, had been enclosed and rented out by the city. A brief time under the plough in the 1970s reduced the floral interest but following restoration and an extensive cattle grazing regime, a number of species have returned including creeping marshwort, bristle club-rush and tubular water-dropwort. The field is designated as a Site of Local Importance for Nature Conservation.

The Introduction Sites

As Apium repens is so rare, it has been considered important to introduce the plant to new locations. Plants were grown from collected seed and were bulked up in the University of Oxford Botanic Garden. Two places around Oxford were tried for the introductions. At New Marston SSSI a damp pony field looked suitable, but the plants soon disappeared, probably eaten by geese. At South Hinksey a pony paddock owned by the Oxford Preservation Trust has proved successful and the plants have spread and flowered well. During 2007 the plants were under water for most of August, but never-the-less dried out enough to flower in September.

Monitoring

Creeping marshwort is monitored annually by volunteers. On Port Meadow, two areas are marked by buried transponders (devices which respond to a radio signal from a retriever) and plants are counted or mapped. This has shown that they move about both by runners and by seedlings germinating from the seed bank in the soil. This is particularly important when mature plants are knocked back by summer flooding. Flooding affects plants most in summer when microbial activity means that oxygen levels in the soil can drop and a build up of ethanol and hydrogen sulphide can reach toxic levels.

Port Meadow is part of the Oxford Meadows Special Area of Conservation and the Environment Agency and Natural England have contracted studies by the Open University of the water level regime and likely impacts.

Future Action

A steering group meets as required to discuss water level management on Port Meadow. The interests of commoners cattle and horses, as well as public access and migrating birds have to be considered.

Further introduction sites in Oxfordshire and in Essex are being sought.

More information

For full details see the Ten Year Report on the Speices Recovery Programme in English Nature Research Report no. 706, 2006 A W McDonald and C R Lambrick.