Did you know?
- The Mansion at Wakehurst is built from Ardingly Sandstone. This was either quarried from the Dog Kennel Pits by the Pinetum or the pit (now a pond) by the South Drive.
- There are over 4,000 SSSIs in England, covering around seven per cent of the country’s land area. They represent the country’s very best wildlife and geological sites.
The Rock Walk leads visitors along the bottom of a series of low cliffs of Ardingly Sandstone that trace the side of Bloomer’s Valley. The geology of this part of the High Weald dates back 140 million years to the Early Cretaceous period, when rivers deposited beds of sand and clay. The area was later covered by the Tethys Sea, which laid down more sand and clay, topped by a layer of chalk limestone.
After many phases of sea retreats and land movements, southeast England rose up to form a huge dome that stretched from the North Downs to France. These land movements were related to the development of the Alps. Over time, weathering cut away the chalk to leave behind the inland sandstone cliffs we see today. Mostly made of Ardingly Sandstone, in places they reach 15 metres high.
Things to look out for
The damp, shady environment provided by the sandstone cliffs at Wakehurst has given rise to a rich flora of ferns, mosses, liverworts and lichens. These are so exceptional, that the site is now part of the Wakehurst and Chiddingly Woods Site of Special Scientific Interest (SSSI). The yew, oak and beech trees growing atop the cliffs have stretched their roots down into cracks in the rocks, and now provide plentiful photo opportunities.
Wakehurst works in partnership with English Nature to conserve this important habitat. The work includes clearing away the invasive plant Rhododendron ponticum, and monitoring the changes that such actions prompt. Two key species that Wakehurst is helping to conserve are the slender-thread moss (Orthodontum gracile), which is classified as critically endangered in Great Britain, and the veilwort (Pallavicinia lyellii), which is considered vulnerable here.