DRY STONE WALLS - MISCELLANEOUS DATA

Many sources refer to species growing on walls, but hardly any differentiate dry stone from mortared walls. One that does is:

Page 138 - On drystone walls , “occasional ferns may occur amongst their moss and lichen floras, mainly emerging from deep within their crevices. But their pteridological interest is mainly limited to the sometimes extensive cappings of Polypodium which can occur along their crests, especially on old walls in rural areas of the most frequent precipitation ...”
 

From Lakeland by Derek Ratcliffe, HarperCollins New Naturalist 2002, p. 167.

“The road verges of the dales have botanical interest, though less than that of the limestone area.”  “The ubiquitous stone walls are an important habitat for mosses and lichens. The drystone kind often have little else, but some support sparse growth of calcifuge ferns, including Parsley Fern. Navelwort is a notable plant but confined to the southwest sector …. “. “Mortared walls are colonised by lime-loving ferns, notably Maidenhair Spleenwort, Wall-rue and, more locally, Rustyback and Black spleenwort."

From Warwickshire’s Wildflowers. Steven J Falk. Brewin Books, Studley, 2009.

Dry stone walls are particularly frequent in the south of Warwickshire, both as field boundaries and in property boundaries in villages such as Ilmington and Whichford. The underlying rock is calcareous, the area representing the north edge of the Cotswolds, so the walls will presumably be of limestone. The book lists the plants found on such walls in general, but gives no data that is clearly for Warwickshire and says that Warwickshire walls have not yet been studied in detail. The data on individual Warwickshire species does not mention dry stone walls. There’s plainly a study opportunity here.


E V Watson (1981) British Mosses and Liverworts (Cambridge University Press, Cambridge)

This book lists species that grow directly on rock (ie not on mortar).

On siliceous boulders in mountain country

Kery and Claire Dalby (2005) Shetland Lichens, publ Shetland Amenity Trust

This book lists all the lichens recorded in Shetland, with a brief note about each.  The following species are noted as occurring on dry stone walls.

Acrocordia macrospora (one wall)
Bacidia scopulicola (inside the walls)
Caloplaca crenularia
C. marina (near shore)
C. thallincola (near shore)
C. verruculifera (near shore)
Canelariella vitellina
Cetraria chlorophylla
Cladonia cervicornis ssp cervicornis
Diploicia canescens (on broch)
Diplotomma alboatrum
Fuscidea cyathoides var cyathoides (widespread on acid walls)
Haematomma ochroleucium var ochroleucium (usually low on walls)
Hypnogymnia physodes (widespread)
H. tubulosa
Lecania baeomma (sandstone walls)
Lecanora actophila (near shore, not often on walls)
L. campestris
L. dispersa (widespread)
L. gangaleoides (often shaded or north-facing)
L. rupicola
L. sulphurea
L. tenera (common)
Lecidea deducens
L. prasinula
L. scabra
L. stigmatea
L. subincongrua
Ochrolechia parella
O tartarea
Opegrapha gyrocarpa (low on N-facing dry stone wall; rare on walls)
O saxatilis
Parmelia glabratula ssp fuliginosa (widespread)
P saxatilis
P sulcata
Pertusaria corallina
P flavicans
P pseudocorallina
Platismatia glauca (widespread)
Porpidia macrocarpa
P tuberculosa (widespread)
Ramalina cuspidata (close to sea)
R siliquosa (very common)
R subfarinacea (common in crofting areas)
Rhizocarpon geographicum
R reductum
R richardii (near the sea)
Rinodina gennarii
Scoliciosporum umbrinum
Sphaerophorus fragilis
S globosus
Tephromela atra (common)
Verrucaria fusconigrescens (horizontal surfaces)
V maura
V nigrescens
Xanthoria parietina (especially near the sea)

Notes: I have not included ones found "at the base of a dry stone wall", "on turfs capping a dry stone wall", "on stone walls", "on walls".  Comments like "widespread" mean I have understood the text to say that the species is widespread on dry stone walls, not just generally, but this interpretation could be mistaken in some cases.
 

Wye Valley

There are said to be lots of dry stone walls here, particularly at Hewelsfield and St Briavels. Hopefully that means they are good floristically.