Constant species

Cymbalaria muralis.

Physiognomy

The Cymbalarietum muralis comprises often very open and fragmentary crevice vegetation in which little hanging clumps of Cymbalaria muralis are the most obvious feature. Indeed, Cymbalaria is the only frequent vascular plant in this community. There can be occasional scattered rosettes of small ferns – Asplenium trichomanes, A. ruta-muraria and Polypodium vulgare – together with patches of Sedum acre, short trails of Hedera helix, isolated tufts of grasses like Poa annua, Dactylis glomerata, Agrostis capillaris and A. stolonifera and some ephemeral herbs but the consistency and cover of such contributions are never high.

More frequent as a group are mosses with small patches of Homalothecium sericeum and tufts of Schistidium apocarpum, Grimmia pulvinata, Tortula muralis, Bryum capillare and Barbula unguiculata occasional to common in the crevices.

Habitat

The Cymbalarietum is characteristic of sunny crevices among the stone- and brick-work of boundary walls and buildings throughout the lowlands of Britain.

Zonation and succession

The Cymbalarietum can be found with other kinds of crevice vegetation where walls have been colonised by different mixtures of species tolerant of the extreme conditions of the habitat. In the warmer south and east of Britain, the Cymbalarietum can be found with the Parietarietum where Parietaria diffusa is the distinctive dominant among the crevices, and Segal (1969) saw this as sometimes a successional replacement for the Cymbalarietum.