Saturday 6 July 2024

Marsh Helleborines in Oxford July 2024

Within the city limits of Oxford there is a narrow and shallow valley of greenery that runs from north to south between housing, two hospitals and all the other usual manifestations of urban life This is the Lye Valley, a Site of Special Scientific Interest (SSSI) in Headington, a suburb of Oxford and part of the Lye Valley Nature Reserve owned and managed by Oxford City Council. It is without argument a delightful surprise  to come across this unexpected  oasis of tranquillity and calm amid all the bricks and concrete that crowd in around it.

Apart from its aesthetic and recreational properties the Lye Valley is ecologically significant as it is comprised of a 14000 years old, internationally rare habitat, a tufa forming, alkaline spring fed fen that represents 1.5 hectares of the only 19 remaining hectares of this habitat in England. It supports over 20 species of plant rare in Oxfordshire of which 14 are also on the Red List of Threatened Species compiled by the  International Union for the Conservation of Nature (IUCN). The Friends of Lye Valley (FOLV) are a group of volunteers who tend the reserve in order to maintain its ecological diversity.

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 between eight and ten thousand years ago. However being situated in a city it is under constant pressure from development as there are a number of different landowners who can and do make planning applications for the various parts of the valley they own to be developed for housing but so far the aim of restoring the whole valley as a natural green area of land with a mosaic of wet and dry habitat remains on course.

Dr Judy Webb who founded FOLV and is an ecologist has said,

Either we make a special case for protecting this most important area or we give up and go home.

Lye Valley is stuffed with rare plants and nationally scarce invertebrates that make it an absolute delight to walk through on the boardwalk that forms the northern part of the footpath that passes down the middle of the reserve and is best known to me for its breeding frogs which come for a brief few days in early Spring to mate and spawn in a series of small ponds right by the boardwalk. see here

Today I had something else on my mind, Marsh Helleborines which although declining nationally grow here in good numbers (1689 flower spikes were counted in 2023) and are to be found close to the boardwalk. However all is not well as the helleborines grow in two distinct wet areas of the reserve. one in the northern part,(North Fen) the other in the southern part (South Fen) and are separated by a large dry area of woodland that has encroached over the years.The hope is to unite the two wet areas by removing the trees, as currently the main pollinator of the helleborines which is a hoverfly cannot traverse the dry woodland area as it is too wide.

Parking the car in an unexceptional suburban road, situated at the northern end of the valley, I walked a few hundred yards south to an opening between the houses that granted access to the valley.

The reserve today was lush with many varieties of wild flora, Common Spotted Orchids and great masses of golden yellow Greater Bird's Foot Trefoil being particularly prominent. 

The North Fen and boardwalk looking north

Following the boardwalk as it gently descended, alongside the Lye Brook which feeds the fens I eventually came to the helleborines, lurking a little way off to the right of the boardwalk, growing amongst orchids, horsetails and various other plants in the boggy North Fen.

Marsh Helleborines are classed as uncommon and in most areas of Britain are decreasing, especially in southern England.They are mosttly found in calcareous fens, wet meadows, marshes and dune slacks in coastal areas of East Anglia, south and southwest England and Wales.They are rare in Scotland but occur on the west coast on some of  the Hebridean islands. In Oxfordshire I know of three sites. all protected reserves where the water levels are maintained so they can thrive.One of the main reasons for their decline is the trend to drier summers and a loss of habitat due to drainage and water extraction.

Marsh Helleborines are very attractive, arguably one of our most beautiful native orchids and can be said to conform with the layperson's idea of what a typical orchid should look like.The flower spike that may be up to 60cms tall can carry up to twenty small flowers, all on one side of the stem and each a masterpiece of colour and composition. This morning each flower's white lip with a citrus yellow base shone with an enhanced brilliance in the sun, surrounded by a bonnet of four sepals of pale greenish white on the outer surface and streaked pink on the inner.

I had no real need to leave the boardwalk to admire these appealing and glamorous orchids as they stood, mute in the sunshine in their boggy habitat.Their often underestimated beauty there for all who cared to see. 

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