Constant species

Parietaria diffusa.

Rare species

Brassica oleracea, Draba aizoides, Silene nutans.

Physiognomy

The Parietarietum judaicae comprises vegetation of crevices and small ledges in which Parietaria diffusa is the only consistent feature throughout, with occasional trails of Hedera helix and Galium aparine. Asplenium ruta-muraria is a scarce associate.

Sub-communities

Homalothedum sericeum-Tortula muralis sub-community. Parietaria tends to be more abundant in this vegetation and the only frequent associates are H. sericeum, T. muralis, Schistidium apocarpum and Barbula spp. Occasionally, there are records for small asplenioid ferns, including A. trichomanes, A. adiantum-nigrum, Poa trivialis and ephemerals such as Bromus hordeaceus hordeaceus, B. sterilis and Arabidopsis thaliana.

Daucus carota sub-community. Parietaria is generally of lower cover here and is often accompanied by clumps of Dactylis glomerata and Festuca rubra, tall herbs such as Daucus carota, Centaurea scabiosa and Euphorbia portlandica with occasional Plantago lanceolata, P. coronopus, Sanguisorba minor, Beta vulgaris ssp. maritima and Sedum acre. This vegetation also provides a locus for the nationally rare Brassica oleracea and, more locally, Draba aizoides and Silene nutans.

Habitat

The Parietarietum is characteristic of sunnier crevices and ledges in walls and on rock faces in quarries and natural cliffs in the warmer and drier southern lowlands of Britain. Parietaria is a somewhat calcicolous plant with a more or less Continental distribution in Britain, being commonest in the south-east of England and extending north and west around the coast (Perring & Walters 1962).