splenium scolopendrium) is often seen, but with a much reduced frond size from samples growing in areas of higher organic matter content, such as hedgebanks and ditches. Whereas fronds in these conditions can grow as much as 60 cm, on limestone walls they tend to between 10 – 20 cm. This reduction in size does not affect dispersal however, and once established populations will persist.
Asplenium trichomanes). The prostrate growth habit of the fronds combined with their large relative length (up to 35cm on limestone walls) and tough, black stalks means this can often be the most evident fern on a wall.
Asplenium ruta-muraria). The young fronds are easily confused with Cardamine spp., however the mature plant has a delicate beauty all of its own.
Asplenium ceterach) is so named because of the rust covered scales that cover the underside of the fronds. Its absence from the centre of the city is unclear as it's response to pollution and light intensity (both of which vary detrimentally closer center) is similar to the species mentioned above.