Saturday, 19 June 2010

Report on the Fern Walk with the British Pteridological Society - 29th May, 2010

For some, as yet unexplained, reason the area of the Mersey Valley adjacent to Chorlton has a very rich Pteridophyte (i.e. Fern) flora and some 24 species have been found between Chorlton Water Park in the east and the Stretford border in the west - a distance of approximately 2 miles.

On a wet Saturday in May four members of the Manchester and North Midlands Group of the British Pteridological Society (Yvonne Golding, Roland Ennos, Michael Hayward and Dave Bishop) and three guests (Charlotte Abbas, Katherine Miller and David Rydeheard) set off from Chorlton Water Park with the intention of seeing as many of the local fern species as possible. First we negotiated a narrow, sunken lane at the rear of the Water Park and bordering Chorlton Golf Course. Here we encountered Male Fern (Dryopteris filix-mas) and a luxuriant specimen of Scaly Male Fern (D. affinis). We then moved on to the inelegantly named Barlow Eye Tip – once a landfill site but now a Site of Biological Importance (SBI). Here we found three species of Horsetail: the ubiquitous Field Horsetail (Equisetum arvense) but also Water Horsetail (E. fluviatile) and Great Horsetail (E. telmateia). The latter species is interesting because in Manchester Museum Herbarium there are specimens of it which were collected from a site nearby in the mid-19th century. The present colony is on the very edge of the site and may have survived all of the various upheavals which occurred around it in the recent past.

Moving further westward along the river bank we came to another SBI known as Lower Hardy Farm. Here, deep in a Birch and Willow copse, is a magnificent stand of Royal Fern (Osmunda regalis). Unfortunately, there is a plan to drive a spur of the Metrolink tram system through this SBI and across the river to Manchester Airport. Various exploratory drilling operations were conducted here recently and the Osmunda plants came within a whisker of being destroyed.

We then inspected the walls of the Withington Sewage Works Pumping Station. Here can be found Intermediate Polypody (Polypodium interjectum), Hartstongue Fern (Asplenium scolopendrium), Maidenhair Spleenwort (Asplenium trichomanes ssp. quadrivalens) and Rustyback Fern (Asplenium ceterach). The latter species is a lime-lover and one would not normally expect to encounter it in South Manchester, but there is probably enough lime in the mortar of the sewage works wall to support it (the photograph above is of A.ceterach on the sewage works wall). Unfortunately, the spring of 2010 had been exceptionally dry (in contrast to the day of our walk!) and many of these ferns were somewhat shrivelled.

In a wet area at the back of Brookburn Road Primary School nearby we found our fourth Horsetail –Marsh Horsetail (E. palustre). Then a single specimen of Hard Fern (Blechnum spicant) was seen clinging to the steep bank of Chorlton Brook; Hard Fern is a rare species locally.

By this time, lunch at the Bowling Green beckoned - but not before we had seen Black Spleenwort (Asplenium adiantum-nigrum) and Wall Rue (A. ruta-muraria) in the wall of the old St. Clement’s churchyard. In the pub I was able to show the group a frond of Common Polypody (Polypodium vulgare) which I had gathered the day before from a site somewhat off our line of march.

After lunch we made our way towards the Chorlton Ees SBI. Passing through a strip of woodland we saw a specimen of Soft Shield Fern (Polystichum setiferum) with rather deeply cut fronds. About 20 years ago I was told that this species was believed to be extinct in Greater Manchester – but evidently not, because since that time it has turned up in several other places.

In the midst of a derelict hay meadow on Chorlton Ees we saw a large and impressive colony of Adderstongue Fern (Ophioglossum vulgatum). This species was reported from this area by Richard Buxton in his flora of 1849 and by Leo Grindon in his flora of 1859, and was then thought to have been lost until it was re-found in 1995.
We also spotted Lady Fern (Athyrium filix-femina) in the course of our travels and finally, in a patch of Birch woodland on the edge of the SBI, we saw Broad Buckler Fern (Dryopteris dilatata), Narrow Buckler Fern (D. carthusiana) and more Scaly Male Fern.

Challenges for the future are to look for Equisetum hybrids and Dryopteris hybrids (particularly the hybrid between Broad and Narrow Buckler Ferns). In addition, the name ‘Scaly Male Fern’ actually covers a complex group of species, and it would be nice to know how many of these we have locally.

Dave Bishop, June 2010

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