Cassop Vale National Nature Reserve

About the Site

Cassop Vale is without doubt the most varied wildlife site on County Durham’s Magnesian Limestone. It is home to a rich and distinctive group of plants and insects.

Magnesian Limestone originally formed in shallow tropical sea some 250 million years ago. It now outcrops as a narrow bank only a few miles in width, stretching from Nottinghamshire to Durham, where it broadens to form a plateau in the east of the county.

Over time, the underlying rock has weathered to form thin lime-rich soils on which unique flowery grassland has developed. This grassland supports plants such as blue moor grass, fragrant orchid, cowslip, rock rose and quaking grass. Rare and uncommon species recorded include globe flower, lesser club-moss and moonwort.

It is one of the UK’s rarest habitats a significant proportion of which occurs in County Durham. Quarrying and agricultural intensification have reduced the extent of this habitat, most sites are now small and fragmented. The 41 hectares at Cassop Vale is one of the more extensive examples.

Hawthorn, gorse and rose scrub thrive on the grassland margins and in places, grades into woodland with hazel, wych elm and ash. This transition of habitats is a valuable feature of Cassop Vale. The woodland contains attractive plants such as wood anemone, dog’s mercury and sanicle. Sanicle is famous for its medicinal properties, indeed the name comes from the Latin sana, meaning to heal. These wooded areas, support breeding birds such as yellowhammer, whitethroat and green woodpecker.

In the valley bottom, fen and swamp vegetation surround a small pond where breeding snipe, little grebe, moorhen and coot can be seen. Hard rush occurs along the line of springs, and the two largest mires support a variety of species including marsh valerian, marsh ragwort, ragged robin and northern marsh-orchid. The pond is fringed with tall reeds and wetland plants, including common spike-rush, soft rush and greater willow-herb. In deeper water, these plants give way to swamp vegetation with lesser pond-sedge, reed mace and bog-bean. Aquatic plants include mare’s-tail, ivy-leaved duck-weed and liverwort.

Nearby, the old spoil heaps of a long-abandoned mine provide further diversity and unexpected colonists such as heather. There are known to be a variety of invertebrates found on the site including populations of the Northern Brown Argus butterfly and least-minor moth. Cassop Vale is worth a visit at any time of the year, but the wild flowers of the Magnesian Limestone grasslands are at their most impressive between April and August.

Cassop Vale

Location

The reserve lies 5 miles (8 km) south-east of Durham City. To reach it, take the A181 out of the city and turn south onto the B6291. Cassop village is reached after half a mile (1 km) and the Reserve entrance is on the right, opposite the Post Office. There is open access to this area, however, visitors are urged to take care on the steep and uneven terrain and to supervise small children closely in the vicinity of the pond. Grid Reference: NZ 335387

Facilities

None.

Similar Sites

Thrislington National Nature Reserve

Little Wood Local Nature Reserve

Hawthorn Dene and Meadow and Beacon Hill

Enquiries

Natural England
Castle Eden Dene
Stanhope Chase
Peterlee
County Durham
SR8 1NJ
Tel: 0191 586 0004

Information on birdlife supplied by Durham Bird Club.