What is a dry stone wall?

Dry stone walls are the dominant field boundaries in some areas. Helpful descriptions are provided by the British Trust for Conservation Volunteers (1994) and Agate et al (1999). The walls are free-standing and rest on a foundation of large stones set in a trench. Layers of stone are then built upwards, without mortar, with the largest stones at the bottom and the smallest at the top. All stones are laid level or dipping outwards, and with stones in successive rows overlapping each other rather than straight on top of each other. Two horizontal structures like this are built with a gap between, leaning towards each other, and the centre is filled with stones of varying sizes to give a solid structure. At intervals, long stones (throughs) are laid across the wall to hold the two sides together. A line of coping stones is commonly laid on top. The illustration below is from a BTCV (1994) pamphlet.

(© BTCV)

The detailed design varies from area to area. Sometimes, throughs are replaced by bonders (or ¾ throughs), which go about ¾ of the way through the wall, and should be adjacent and overlapping to provide the strongest structure. Coping stones may be omitted, or laid flat across the top. Walls which look similar on their visible side but supporting earth on the other are not included in the definition.

What do we know of the flora of dry stone walls?

The flora of dry stone walls has been little investigated, almost all work on wall flora being based on walls generally (Darlington 1981; Segal 1969; South Court Environmental Ltd 1994). The only directly relevant sources located are Payne (1989), Williams (1988) and Watson (1968). A number of people have become interested in further investigation and this website is a means of collating the results as they appear.

What do we need to know?

A number of key questions can be identified relating to the flora of dry stone walls and these are listed below. Investigations for them are already in progress, and it is hoped to include results on this site soon.

1. What kinds of plants, lichens and fungi grow on dry stone walls?

2. Which of these organisms grow on limestone dry stone walls and which on walls constructed of acid rocks?

3. Is the flora of dry stone walls significantly and consistently different from that of mortared walls?

4. Can the flora of dry stone walls be distinguished from the flora of the surrounding environment?

5. How does the flora of dry stone walls fit into the National Vegetation Classification?

6. How can the flora of dry stone walls be conserved and enhanced?

Further information from

John Presland, 175c Ashley Lane, Winsley, Bradford-on-Avon, Wilts BA15 2HR. Tel 01225 865125

References

Agate E, Brooks A and Adcock S (1999). Dry Stone Walling. BTCV, Doncaster.

British Trust for Conservation Volunteers (1994) How to dry stone wall. BTCV, Doncaster.

Darlington A (1981) Ecology of Walls. Heinemann Educational, London.

Payne R M (1989) The flora of walls in the Chew Valley. Somerset Archaeology and Natural History 133: 231-242

Segal S (1969) Ecological Notes on Wall Vegetation. Dr. W. Junk N. V., The Hague:

South Court Environmental Limited (1994) What’s on a Wall? The Ecology of Walls, edn 3.South Court Environmental Limited, Northampton.

Watson E V (1968) British Mosses and Liverworts. Cambridge University Press, Cambridge.

Williams L. (1988) Observations on the flora of wall habitats on Yell, Shetland, in J. A. Fowler ed. Ecological Studies in the Maritime Approaches to the Shetland oil Terminal: Report of the Leicester Polytechnic to Shetland, August 1986 and July 1987. Leicester Polytechnic, Leicester.