Limestone grassland is a very rare habitat in the UK. It supports a wide range of plants including thyme, horseshoe and kidney vetches, rock rose and salad burnet. Rare butterflies, such as the chalkhill blue, depend on wild flowers which specifically grow in lime-rich soil. Limestone grasslands are typically managed as pasture, and livestock grazing is an integral part of the management of these sites.

Many limestone grasslands have been lost over the last century as fertilisers have been added to fields to increase agricultural production by adding nutrients to the soil. This encourages faster growing grasses, like rye grass, that use soil nutrients to quickly grow high, which blocks out light to wild flowers. The commercial livestock breeds that are mostly reared now can struggle to put on weight and condition when grazed on rough pasture like limestone grasslands. This has led to some sites being under grazed, which can allow rank grasses, like tor grass and scrub, to encroach on the grassland, shading out the wild flowers.

Limestone grasslands require grazing to enable wild flowers to compete with more vigorous grasses. It is best to graze cattle and sheep throughout the majority of the summer, autumn and winter and to take the stock off at the end of March for spring growth and early summer flowering and seed setting. Stocking rates need to vary depending on the vegetation cover.

Large amounts of scrub on grasslands can develop if no management is carried out for a period of time and stocking rates have to be reduced in the first instance so that the cattle and sheep have enough to eat. Scrub control by machine or hand may be required to help remove this invasive habitat, but scrub is an important habitat in its own right and some should be left for insects and nesting birds.

Access to water may be an issue on limestone - a ‘karst’ landscape - as many streams disappear into underground caves to re-appear at the bottom of the hill. Piped water is suitable where pressure allows, but in other areas ponds or bowsers may be the only option. In drier years it may not be possible to graze these sites if water sources dry up and water cannot be piped. Sheep drink minimal water, but do require access to a water source. Cattle, horses and ponies must have access to water all year round.

Horseshoe vetch is a spreading wild flower which is a member of the pea family. It has yellow flowers between May and July and the sinuous seed pods break up into horseshoe segments. This is a very rare species which prefers to grow in areas where the vegetation is closely cropped. It is the only food plant of the chalkhill blue and adonis blue butterflies.

Kidney vetch is another member of the pea family that flowers between June and September. The plant produces yellow flowers in a coat of long white, woolly hairs. There are a number of sites with kidney vetch scattered along the southern scarp of the Mendip Hills. The UK’s smallest butterfly, the small blue feeds solely on kidney vetch.

Thyme is a distinctive species of limestone grasslands. It is one of the most commonly recognised plants as we use it for flavouring food. It tends to grow in clumps, particularly in very lime-rich, thin soils such as around limestone rock outcrops. Thyme is actually part of the nettle family and has purple flowers between May and August, although its leaves are identifiable throughout the year.

Salad burnet lives up to its name as the leaves are edible and smell like cucumbers when crushed. It is a low growing species with a base rosette of leaves and has a flower spike which is made up of many flowers without petals. The flower spike is tinted red by the feathery stigmas when it opens.

Common rock rose is a low growing member of the rose family with delicate yellow flowers between May and September. It tends to grow in mats which can cover very large areas of lime rich soil and is used as a food plant for many insects including the brown argus butterfly.

Greater knapweed has large purple flowers similar to those of the thistle family of which it is a member. It is very similar to its more common relative black knapweed, but grows on lime-rich soils. Bees and butterflies, like the marbled white butterfly, use this valuable nectar source which can be confused with field scabious when it is not flowering.