This small nature reserve lies at the south end of Stanborough Park and comprises mainly reed beds, sedge marsh and wet willow woodland, all rare habitats in Hertfordshire.
The reserve is important for species such as reed and sedge warblers, water voles and water birds.
A short trail leading from Stanborough Park gives views over the marsh. Access to the reed marsh is restricted.
All management is undertaken by the Herts and Middlesex Wildlife Trust who lease this reserve from the council. Work includes the annual cutting of the reed and management of the willow by pollarding and coppicing. Grants from the Environment Agency have helped to fund the re-wetting of the reed beds, by scraping away accumulations of silt and sludge, to provide better and wetter conditions for reed growth. Re-excavation of the ditches allows better control of water levels on the reserve. Regular bird-ringing continues to show the importance of this nature reserve for wetland and farmland birds.
The Herts and Middlesex Wildlife Trust manage a volunteer group for the marsh.