The Temperate House: History and Restoration
Tender woody plants from the temperate regions of the world have always formed an important part of Kew's glasshouse material. Initially, these plants were accommodated in the Nash Conservatory, the Orangery and several other houses, but by the mid-nineteenth century, the collection had grown so large that the need for a large temperate greenhouse had become overwhelming. It was envisaged that the new house would complement the Palm House, built between 1844 and 1848 to house the tropical woody collections, and the T-range (the predecessor of the Princess of Wales Conservatory) where the tropical herbaceous collections were displayed.
Construction
Approval was eventually given for the construction of a Temperate House and, in 1859, the Government allocated £10,000 for the purpose, directing Decimus Burton (1800-81) to prepare designs for this 'long-desiderated' conservatory. The contract for the building was awarded to Messrs Cubitt and Co., whose final account for the work (the main block and octagons) amounted to £29,000.
The chosen site, set deep in the then new arboretum, was raised 2 m by the formation of a huge terrace, composed of sand and gravel excavated from the lake site. Determined by Kew's requirement for a well-ventilated structure, the house was designed as a straight, rather than curvilinear, shape. Further requirements for easy repair and heating led to wood being chosen in preference to iron for the glazing bars. For visual reasons, a decorative cornice was requested at the eaves.
Work began in 1860, with the octagons being finished in 1861 and the centre block in 1862, but the building was not completed immediately. Although the foundations for the wings had been partially laid, work was postponed indefinitely in 1863 and it was not until 1894 that approval was given for the final stage with work restarting in August 1895. The south wing was finished in 1897, followed by the north wing, built to a modified design (after the bankruptcy of the original contractor) in 1898. The completed building, which is the largest glasshouse at Kew, measures 180 m by 42 m at its greatest length and breadth, and covers an area of 4800 m2, about twice the size of the Palm House.
Plants were quickly established in the new glasshouse. The main block always featured interesting subtropical crop plants, and when the south wing was added in 1897, its planting emphasised others, notably fruit trees, such as mango (Mangifera indica) and papaya (Carica papaya) along with ornamentals, such as crepe myrtle (Lagerstroemia indica) and some succulent plants from Mexico and the Old World. The north wing was planted from the first with Himalayan rhododendrons.
During the early decades of the present century, the collections were enriched by new plants coming from China. In 1924, a heavy teak annexe was appended to the north octagon to hold the influx of new Chinese rhododendrons. Unfortunately, the low light transmission of this structure proved suitable only for shade-tolerant camellias. It was decided not to rebuild it after its removal in 1977, since the differing construction also compromised the clarity of Decimus Burton's original design. Furthermore, many of the plants that the annexe originally housed are now grown outside at Wakehurst Place, where the conditions are much milder and wetter than at Kew.
Problems
As the collections continued to increase, congestion, and consequently poor growth, became a pressing concern. Even with the relief provided by the transfer of plants to the new Australian House (now the Evolution House) in 1952, the centre of the heavily structured main block had become filled with large evergreens, principally conifers and palms, by the 1960s. Their shading effect, coupled with the building's low light transmission (sometimes down to under 30 per cent of incident light), severely restricted the growth of the ground flora. The heating system was also giving continuing problems, a legacy of the original design. The boilers, sited underneath the octagons, were poorly insulated and produced an environment above quite unsuitable for the growth of temperate plants. Additionally, heat distribution to the wings was less than satisfactory.
Restoration
Many other problems beset this house over its long history, but the cumulative effects of more than a century's decay, with glass, masonry and metalwork falling in high winds, necessitated a full restoration. A survey and structural analysis were undertaken in 1972 by the consulting engineers, Posford, Pavry and Partners (now Posford Duvivier). They found that, in many cases, rust had weakened the members beyond repair and complete replacement was necessary.
In 1974, the Property Services Agency of the Department of the Environment decided to call in the consulting architects, Manning, Clamp and Partners, to prepare in collaboration with the engineers, a full restoration scheme which would meet both the functional and historic requirements of this scheduled building. Every structural element of the building in need of attention was measured, specified and located on a grid (in plan and elevation) before being cross-referenced to the survey drawings.
The architects studied the original design to prepare the enormously detailed documentation necessary for a contract project for the restoration. They carefully restored the original roof form and glazing pattern, which, together with the ventilators, had been altered by repairs to the main block and had not been continued in the later-constructed wings. The opportunity was also taken to improve the function of the house by eliminating earlier design problems. The use of narrower glazing bars greatly increased the light transmission and allowed the addition of semi-automatic ventilators.
To improve efficiency, the heating system was also improved. The unsightly coils of pipe, which lined several of the centre paths, were replaced by radiators and high-level radiant panels. The boiler house is sited in the nearby Stable Yard and the heat-exchangers, which replaced the boilers in the octagon basements, take little space. Some of the extra space provides staff facilities in the south octagon. Other improvements included the repairs of the six large-capacity underground rainwater tanks and the restoration of the decorative cornice.
The same attention to details was exercised on the internal layout and planting. A reduced and simplified secondary path system, of paving rather than the earlier tarmac, supplements the strongly cruciform main path system. The larger beds that resulted have provided space for the inclusion of water features and sculptures. To contrast the warmer, drier Mediterranean aspect of the southern end with the cooler, moister northern end, where the emphasis is on Asian plants, different types of rock are used.
The restoration work kept carefully to schedule, and the house was completed in the autumn of 1980. As parts of the house were finished, the horticultural staff moved back and the final planting was undertaken during the summer of 1981. The restored house was officially reopened by HM The Queen in May 1982.
For the first time, the collection has been arranged geographically, as Decimus Burton originally intended. Though modern technology, materials and layout have significantly reduced maintenance and halved the labour input, the range and number of species displayed has been maintained. The plants grew at a prodigious rate in the restored house, obviously relishing the improved conditions. Many plants bloomed for the first time, including the king protea (Protea cynaroides), which last flowered in Victorian times.
