areas of calcareous grassland are found over the thin, rocky mineral
soils derived from the Carboniferous Limestone or Dolomitic Conglomerate.
These are especially characteristic of the southern scarp of the
Mendip Hills, in areas where abundant rocky outcrops and steep slopes
have rendered cultivation impractical. Many of these areas have been
grazed by sheep for centuries, and over time have developed a very
rich flora. Typically, more than twenty species of plant are present
per square metre of turf, and some of the richest areas may support
thirty species or more. Apart from their high diversity, other striking
features of these grasslands include a lack of dominant species,
extensive cover of herbaceous plants, and the diminutive stature
of many of the species.
Mendip limestone grasslands vary in composition, but almost invariably
support a constant suite of lime-loving species, including salad
burnet, small scabious, sheep's-fescue and wild thyme. Many orchids
are also characteristic of unimproved limestone grassland, some commoner
species including common spotted orchid, pyramidal orchid and bee
Bee orchid, Ophrys apifera.