Boundary House Fen - Saturday, 29 June 2024

Blog by Sally, photos by Eleanor, Kevin and Sally

Nine Green Gymmers turned out for this week's session at Boundary House Fen on Frilford Heath Golf Course SSSI, led by Kevin. As the gate to the compound car park had not been opened for us, we parked on the verge. Kevin had parked further along the Abingdon Road, leading to Tubney, so we did not have to carry the tools with us. As we walked by the side of the fairway there were lots of viper's bugloss in flower with its startling blue flowers, along with a carpet of birdsfoot trefoil (beloved of pollinators) and lady's bedstraw, a specialist of dry calcareous grassland, with its froth of tiny yellow flowers.

We worked under the direction of consultant ecologist, Rod d'Ayala, who had arrived before us and had made a head start with brush-cutting the grassy slope leading from the tee to the fen itself. Our main tasks were to continue with removing hemlock to prevent its incursion onto the fen, raking up the cut material from Rod's brush-cutting and scything two areas. In the first of these, creeping thistle has been spreading on the slope, which we need to stop from taking over on the fen, as well as continue with cutting reed, which grows very densely thereby blocking out light for the rarer calcareous fen specialists that we are encouraging to flourish. Jim set about scything this patch.

The second area involved scything a route along the runnel to the dam at the spring head and also scything down a lot of lesser water-parsnip, some of which Rod had transplanted so that its roots would stabilise the bank of the runnel to prevent water seepage here, as the idea of the runnel is to 'wet' other areas of the fen. Fens are wonderful sequesters of carbon, but to function properly, they need to be wet allowing natural shallow pools and streams to form, all fed by springs. In this area of Oxfordshire, the water percolates through a layer of chalk thereby creating a calcareous (or alkaline) fen. Fens are a rare habitat, but calcareous fens are even rarer - so it is even more important to protect the specialist plants (and invertebrates that depend on these plants) by restoring the fen to its former glory.

Dieuwke, Eleanor and Lesley set about removing the hemlock, which was dug up where possible, while Carolyn, Kevin, Graham and Roger started raking up after Rod and Jim.

The scythers had to be careful as many of the orchids, including the common spotted, are in full bloom and patches of the fen ecosystem engineer, marsh lousewort, as well as stands of marsh thistle all had to be avoided being cut. Figwort was in bud and it was lovely to see a few butterflies about and both the beautiful and the banded demoiselles graced us with their presence. There were also some hoverflies but very few bees, which is of great concern, and we hope this is not due to the spell of very hot weather last summer, combined with a very wet and cool spring.

Breaktime was called at the usual time of 11.00, which was very welcome as we had all begun to get rather warm and thirsty in the glorious midsummer sunshine. Dieuwke bade farewell to us at this point as she was volunteering with afternoon teas at St Ethelwold's in aid of the Kennington Memory Club and a few of us pledged to visit to support this worthy cause.

Rod was keen to stem a breach to the dam using the cut arisings from around the runnel, which Dieuwke had already started raking up before break. After break, Eleanor and Lesley helped with this and the arisings from Rod's brush-cutting were dragged in place and firmly stamped down to build up the level and block the leak. The cut material will rot down to form peat eventually. In the process, Rod spotted a diving beetle, which we think might be Colymbetes fuscus.

Meanwhile, Jim was busily scything reed and Roger, Carolyn, Kevin and Graham helped rake up the cut reed into a heap.

The time flew by and it was soon 12.30, the appointed hour when we stop what we're doing and pack up the tools. Looking back, it was amazing to see what we had achieved with so relatively few people and in only a few hours. We were almost at the point of departing when we spotted Susan coming our way! She had said she would be a bit late and had it in mind that we finished at 13.00! It just happened to be her birthday and she had kindly brought some rose lemonade and a couple of cakes - coffee and walnut and chocolate! So we stopped what we were doing and welcomed her. After which, we sang "Happy Birthday", before tucking in to a piece of cake (well, it would have been rude not to!) and toasting Susan's good health. At the reminder of next week's session at Marcham for Himalayan Balsam pulling, Kevin remembered that he had seen some Himalayan Balsam, an invasive non-native species, which Rod set off to pull as that will be the last thing we want to take over the fen - it spreads prolifically by seed-popping but is shallow-rooted and destabilises river banks. It also prevents other, native, plants from growing. Although bees love it, it is not a good source of pollen for their young.

We said goodbye to Rod and left him with his brush-cutter nearby a patch of Himalayan Balsam. We look forward to returning at the end of next month, hopefully with a few more scythers and rakers, to continue the good work.