Nature Reserves

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Lye Valley, OxfordWebsiteStreet MapGoogle MapPhotos

Lye Valley
Managed by:Oxford City Council
OS grid reference:SP 544 056 (Reserve - North)
SP 546 052 (Reserve - South Fen)
SP 549 060 (North Entrance)
SP 547 052 (South Entrance)
Nearest postcode:OX3 7JT (Reserve - North)
OX3 7HP (North Entrance)
OX3 7EP (South Entrance/Reserve)
Usual work:Fen raking, scrub clearance, step-building, pond maintenance

Lye Valley fen is a secluded area situated in Headington, Oxford, part of which has been designated as a Site of Special Scientific Interest (SSSI). The site contains a range of habitats including spring-fed lowland fen, a variety of ponds, and wet woodland with small representations of lowland calcareous grassland, wood pasture and parkland. Lye Valley has one of the best examples of a calcareous valley fen, a nationally rare habitat. The plant and animal species of the Lye Valley fen are thought to have lived there since they colonised the spring areas after the retreat of the last ice age perhaps 8,000 to 10,000 years ago.

OCV tasks at this site often include raking up reeds and grasses from the fen to restrict the growth of grasses and promote the survival of wild plants. We also clear scrub and overgrown hedges, build steps to increase access to the site and assist with pond management and creation.

Fen raking in the sunshine


Lye Valley is split into two distinct parts. The first area comprises of 1.8 hectares of land starting at the Slade and ending at the base of the Churchill hospital car park. The second area is a much smaller section covering around 0.54 hectares of land situated between the Cowley Golf Course and South Park.

Around 500 years ago, Lye Valley was an open water source which turned into a reed swamp and later filled in with peat to become the fen that we see today. The rich calcareous fen has been retained due to the high calcium, low nutrient spring water that controls its development. Until the 1930s, the main areas of the Lye Valley were a mixture of fen, marsh and rough grassland. The wet woodland is a consequence of grazing in the first half of the twentieth century.

Flora and Fauna

In the past, more than 300 plant species have been identified at Lye Valley, including the first recorded sighting of the grass-of-Parnassus (Parnassia palustris) in Britain. Rare species of rushes are found in the fen including the black bog rush (Schoenus nigricans) and the blunt flowered rush (Juncus subnodulosus). Numerous varieties of sedges, mosses, liverworts, ferns, grasses and fungi have been identified at Lye Valley. The varieties of sedge growing at the site include cyperus sedge (Carex pseudocyperus) and greater tussock sedge (Carex paniculata). Grasses found at Lye Valley include perennial rye-grass (Lolium perenne), purple moor-grass (Molinia caerulea) and cocks-foot grass (Dactylis glomerata), whilst fungi species include blushing bracket (Daedaleopsis confragrosa), bonnet mycena (Mycena galericulata) and jews ear (Auricularia auricula judae).

There are also a wide range of trees, shrubs and flowering plants at Lye Valley, including alder (Alnus glutinosa), black bryony (Tamus communis), white bryony (Bryonia dioica), sloe (Prunus spinosa), ash (Fraxinus excelsior), grey and crack willow (Salix cinerea and Salix fragilis), ground elder (Aegopodium podagraria), various thistles (including Cirsium palustre and Cirsium arvense), wild angelica (Angelica sylvestris), hogweed (Heracleum sphondylium), marsh pennywort (Hydrocotyle vulgaris), yellow flag (Iris pseudacorus), water mint (Mentha aquatica), silverweed (Potentilla anserina) and parsley water-dropwort (Oenanthe lachenalii) to name just a few.

The ponds at Lye Valley each contain species including the water figwort (Scrophularia auriculata), wavy bittercress (Cardamine flexuosa), water mint (Mentha aquatica), and woody nightshade (Solanum dulcamara). The species found in each pond varies greatly, each providing a slightly different habitat.

The area is known for its variety of bird life including reed warblers, redwing, fieldfares, siskin, reed bunting, redpoll, long-tailed tit and the grey wagtail. Many insect and invertebrate species are present in and around Lye Brooke including species of the rare soldier fly, whilst deer, moles and foxes are among the mammals thought to be active in the area.

Conservation Management

Walking down the valley, one could identify many ecological and mechanical engineering schemes that have been put in to place to ensure the survival of this beautiful habitat. These include planting of tree rows on the steep-sided gully, using check dams to slow the water flow and also using methods such a rip rap and enkamats (mesh used to stabilise plant growth and prevent erosion). To maintain the calcareous fen, it must be kept low in nutrients to restrict the growth of grasses and promote the survival of wild plants. This is achieved by cutting the grass, sedge and reed and then raking up the debris to prevent the compost from enriching the soil.

OCV have assisted at this site by visiting it every year and clearing areas of scrub, grass and reed and cutting overgrown hedges. OCV have also built steps to increase access, whilst protecting the precious flora and fauna. Ecological maintenance of the diversity of ponds at the site is another task that OCV have assisted with. This includes the creation and extension of a pond at the site in order to increase the diversity of habitats within this wetland.

Also see the website for the Friends of Lye Valley:


A few hundred years ago, Lye Valley was maintained using grazing and reed cutting. The wide variety of plant species in the extensive areas of calcareous fen and calcareous grassland attracted many early botanists from the Oxford University from the 1600s to the 1920s. Lye Valley was recognised as a nationally rare habitat in 1972 and formally recognised in 1987 under the Wildlife and Countryside Act 1981. The northern part of the SSSI falls under the jurisdiction of Oxfordshire County Council and is part of a local nature reserve.


The entrance to the Northern part of the reserve is a track that is 100 metres south of Girdlestone road off The Slade and the path continues across the golf course to Cowley Marsh in Headington, Oxford. The path that leaves The Slade between Gridlestone Road and Peat Moors is marked with a green public footpath sign to Lye Valley. North Entrance

The entrance to the Southern part of the reserve is from the road named 'Lye Valley' along an unsigned path beginning at a wooden gate by a telegraph post, directly opposite house number 14. South Entrance