Castle Bottom National Nature Reserve

An important valley mire, with associated heathland and woodland habitat

castle bottom nature reserve

About the site

Castle Bottom National Nature Reserve is a small lowland site. It contains one of the most important valley mires in southern England. The reserve is a Special Protection Area (SPA) because of its important bird populations. 

Visitors can enjoy the site via the network of permissive footpaths. These link up with existing footpaths and bridleways outside the boundary of the reserve. Please keep to these footpaths so the habitats and their associated species are not disturbed.


The reserve contains what is thought to be a Bronze Age burial mound c1800-550BC. This mound and a tumulus to the south of the site gives some indication of past land character. These burials were usually placed in open country which means it was open heathland at that time. Despite the name there is no evidence of a castle on or near Castle Bottom.

Natural history 

The site supports a wide range of habitat and community types. Two valley mire complexes run through the reserve. Each has a small acidic stream running through the centre. Water seeping out of the gravel beds at seepage steps feed the mires. Above the mires on the drier slopes is Ling dominated heathland, with scattered birch and pine scrub. This becomes cross-leaved heath heathland on the lower slopes below the seepage steps.


Some ecologists and environmentalists consider lowland heathland to be more threatened than the rainforests. Britain is an important country for this, because it has a large proportion of the world’s total. Hampshire alone has around 10% of it. Heathland has been lost to development, forestry or sand and gravel extraction. The remaining fragments of heath are often disturbed by these processes taking place around them. Many of the remaining pockets of heathland are separated by many miles, which is a serious problem for less mobile species. 

Many heathlands were once registered as common land, giving local people special rights to graze animals or gather wood for fuel. Many of these rights have now lapsed over the years. It is therefore crucial to the survival of our remaining heathlands that we continue some of these traditional practices.

A herd of six Exmoor ponies roams free across the heathland keeping invasive grasses, birch and bracken to a minimum, whilst breaking up the heather structure and creating bare ground. They do this by munching away at the vegetation, roaming across the heath and through the mire, helping to manage the site in a more subtle way.

Contact us

North Area Office, Basing House, Redbridge Lane, Old Basing, RG24 7HB

Phone 01252 870425

Email [email protected]