Walls...again

I have a morbid interest in walls. Perhaps that is an exaggeration as my interest is not, I hope, unhealthy, but I do regard them as a fascinating habitat. What is the name for someone with such an interest: a muraphile perhaps - or just a wally!

Anyway, when I found myself ten minutes early for a bus in Banbury I took a look at an adjacent wall and was not disappointed. The wall was composed of blue brick - not the most promising of habitats - but it was host to a wide variety of organisms. A few vascular plants had taken root, most obvious of which were some Buddleias, Buddleja davidii. The local authority will need to remove these quite quickly or their roots will begin to split the wall. Less of a danger was posed by a tiny, stunted crucifer about a metre away. The plant was not in fruit (and fruit are very useful in determining a species) but the minutely hairy leaves suggest it was Common Whitlow-grass, Erophila verna, a highly variable plant which favours dry walls.

Photo 1.  Buddleia and the lichen Xanthoria parietina

Near to the Buddleia was a bright yellow patch of the abundant lichen, Xanthoria parietina. At least three other species were present but, having no claim to be a lichenologist, I am not prepared to put a name to them.

Mosses were also common. The grey species at the top left of Photo 2 is Grimmia pulvinata, but Bryum argenteum and Tortula muralis were present too. The mosses, like lichens, have no true roots so the lack of soil is of little consequence.

Photo 2. Common Whitlow-grass?

By this time my bus was imminent so there was no time to peruse further, but there is no doubt that, even in an urban, rather polluted area, there is an abundance of interesting organisms to be seen. The mortar of walls is usually lime-rich and the walls themselves are often sun-baked and very dry. These circumstances, together with limited competition from taller plants provide a very special habitat and provide a home for some organisms found nowhere else.