After recently noticing a single clump of the rare wall-inhabiting fern Rustyback (Asplenium ceterach) by the entrance to Walkley Library, I was alerted to the fact that the nearby gennel connecting Walkley Road to Parsonage Street held a very sizeable population, estimated to hold more than 80 plants. Since then I have found two more very small populations of Rustyback in Walkley, one at the corner of Greenhow and Camm Streets, and one plant in another gennel connecting Fern Road to Walkley Bank Road. It seems likely that the large 80+ population is acting as a source for these three more recent colonisations.
Rustyback is only known from a handful of sites in the Sheffield conurbation, including a good population on the wall next to the entrance of Norfolk Park on Norfolk Park Road, so its pleasing to see that it is apparently spreading, and highlights the especial importance of protecting sites with large populations that can act as sources for the colonisation of new territory. Ferns on walls are great for winter identification, and a good key is available freely at http://www.wildlifebcnp.org/ecology-resources.htm.
Don’t forget that photos of wall ferns uploaded to the Sorby Flora flickr group (http://www.flickr.com/groups/sorbyflora) will also contribute to an updated Sheffield Flora.
Rustyback (Asplenium ceterach) at Walkley Library, Sheffield