The Conservative Wall ("The Case"), Chatsworth

The Conservative Wall dates from the years when the 6th Duke of Devonshire and his gardener Joseph Paxton were reshaping the gardens at Chatsworth. Sources differ on its beginnings: the listing description says it was built around 1832 as a forcing wall by Paxton and one Robertson, whereas the estate credits Paxton with designing it in 1838. In its first form the heated wall was protected by projecting wooden panels, supplemented with canvas curtains in the hardest weather.

In 1848 Paxton replaced this arrangement with a proper frame of timber and glass; the listing places the conversion into a greenhouse between 1848 and 1850. These were Paxton's busiest years under glass at Chatsworth: the Great Conservatory, designed with Decimus Burton, had been completed in 1840, and the Lily House for the giant water lily went up in 1849-1850.

Both of those great buildings were demolished in 1920, while the Conservative Wall has remained standing and in cultivation. It has been listed at Grade II since 12 July 1967, and the estate now calls it "The Case". As Wikipedia points out, the name carries no political meaning: it refers to a shelter for conserving tender plants.

The listing description gives a length of 331 feet (about 101 metres) and a width of 7 feet (about 2.1 metres), stepped up the hillside; the estate quotes 91 metres. The structure is divided into eleven units: a taller, projecting central section with five units on either side.

To the north, a sandstone ashlar wall without any openings forms the back of the house. To the south, a coped ashlar plinth carries the timber-and-glass superstructure, each unit being divided into four bays by vertical glazing bars beneath a decorative valance and parapet. The central entrance is reached by a flight of stone steps and opens through a tall round-arched doorway with a traceried fanlight.

The wall is threaded with flues and hot-water pipes, a system the estate describes as ingenious, which keeps winter temperatures high enough for half-hardy plants to thrive. The principle is still that of the original forcing wall, simply enclosed under glass since 1848.

The estate presents "The Case" as a protective cover for tender plants against Derbyshire's changeable climate. Figs, peaches, nectarines and apricots are grown here, together with a range of shrubs; according to Wikipedia, the ten side sections are given over to fruit and camellias.

The oldest residents are two Camellia reticulata 'Captain Rawes', planted in 1850, just after the wall was glazed, and still in place. Chatsworth's camellias have also won many prizes. The pairing of fruit trees and flowering shrubs reflects the building's double history as a forcing wall turned glasshouse.

The Conservative Wall runs along the northern boundary of the garden, from Flora's Temple, a small classical building of 1695 housing a statue of the goddess by Caius Gabriel Cibber, up to the stables. About fifty metres to the south stands the First Duke's Greenhouse of around 1698, one of the largest and best-preserved seventeenth-century greenhouses in the country, close to the modern Display Greenhouse. The walk can continue to the maze laid out in 1962 within the foundations of the Great Conservatory. The garden covers about 42 hectares and receives some 300,000 visitors a year.