Glass distinction

RHS Journals

The Garden
February 2007

Glass distinction

The Bicentenary Glasshouse at RHS Garden Wisley is due to open this summer. Phil Clayton explores some iconic glasshouses of the past, and previews the Society’s new landmark structure, built entirely through the generosity of RHS members and its wellwishers

For years it seemed the days of great glasshouses were over. A few notable relics from the Victorian heyday of glass survived, but most were in a state of crumbling disrepair; many were bereft of plants and closed to the public. Modern replacements often owed more in appearance to commercial growing-houses than the palaces of horticulture pioneered by visionaries such as Joseph Paxton and Decimus Burton.

But over the last 20 years there has been a steady revival in the fortunes of the glasshouse, gathering momentum since the turn of the millennium.

Covered revival

In the UK, many old glasshouses have been restored, ensuring future survival, while, excitingly, brave new structures have also appeared - some not of glass at all. Notable examples include the Eden Project biomes in Cornwall, opened in 2001. Among more traditional structures, most significantly for members of the Society, is the new Bicentenary Glasshouse at RHS Garden Wisley, due to open in early summer this year. This structure replaces the old range of houses dating from the late 1960s, adapted from a commercial house.

RHS and the history of glass

The story of the RHS is closely interwoven with the evolution of glasshouses, especially in the early 19th century.

The first ‘glasshouses’, dating from the 17th century, were simple structures for overwintering tender plants, with solid roofs and large, often removable front windows of small glass panes. Larger and grander orangeries, such as the fine example at the Royal Botanic Gardens, Kew, followed soon afterwards.

At the beginning of the 19th century new possibilities opened up, thanks partly to the advent of wrought iron, the end of a costly glass tax and the manufacture of larger, single sheets of glass, as well as more efficient heating systems. Demand also surged, as plant collectors bought back tender marvels from the farthest corners of the earth.

The latest glasshouses now had glass roofs and a lighter, slender framework allowing greater light transmission and better plant growth. The most desirable were curvilinear structures with elegant arching outlines, thought to aid plant growth, such as the Palm House at Bicton Park in Devon, dating from 1825.

The RHS was founded in 1804, when important advancements in glasshouse design were under way. Perhaps the one person who had the most impact was Joseph Paxton, who had worked at the Society’s garden in Chiswick for three years until 1826, when he became Head Gardener at Chatsworth in Derbyshire. He used his innovative ‘ridge and furrow’ roofing, allowing optimum light levels to reach plants inside, on the largest glass structure of the day: Chatsworth’s ‘Great Stove’, built in 1836 to house the plant collection of the 6th Duke of Devonshire. Paxton’s crowning achievement, however, was the Crystal Palace, built in Hyde Park for the Great Exhibition of 1851.

Chiswick, Kew and Kensington

By 1840, a spectacular new conservatory was under construction at the Society’s Chiswick garden. The proposed curvilinear structure was to be some 152m (506ft) long, in the form of a central dome with two wings, and made of wrought and cast iron. Paxton felt the design unnecessarily expensive, believing a wooden ridge-and-furrow structure better. Only one wing was completed in the original iron, but this did not hold ornamentals for long - by 1860 it became a vinery.

By contrast, the Palm House at Kew, built in 1844, proved a great success architecturally, although it was difficult to heat. Designed by Decimus Burton for Kew’s palm collection, it is arguably the finest surviving Victorian glasshouse.

In 1861 the RHS opened a new garden in Kensington, London (near the Natural History Museum), complete with a large, curvilinear conservatory, but this and the 70ha gardens were short lived: by 1888 the Society retained only its garden at Chiswick.

Elsewhere glasshouses continued to appear. At Kew, the century-old ‘Great Stove’ was demolished, and in 1861 work started on Burton’s vast Temperate House, a structure not completed until 1891.

New glasshouses were also added at Edinburgh (Palm House), Glasgow (the Kibble Palace, which was moved to the gardens in 1873) and later, Liverpool (Sefton Park Palm House).

Dark clouds gather

In 1903, the RHS acquired its garden at Wisley, but there would be no showcase glasshouse here. Instead there was to be a range of smaller houses, in front of the laboratory, across the current canal

This was a time of changing fortunes. The First World War depleted the workforce, and the later depression made heating bills hard to afford. Chatsworth’s ‘Great Stove’ was deliberately blown up after most of the plants inside had died from cold, while the Crystal Palace burned down in 1936. Worse followed after the Second World War. Maintenance costs saw off most private conservatories, while public glasshouses were now in a poor state. Even Kew’s Palm House was almost demolished; fortunately, it was restored and reopened in 1959.

In the late 1960s, a new glasshouse at Royal Botanic Garden Edinburgh replaced a decrepit Victorian range; in 1970 the familiar series of glasshouses at Wisley was opened - workmanlike and practical, but hardly inspiring.

During the 1980s Kew restored its Temperate House and completed a near rebuild of the Palm House, while in 1987 the dazzling, state-of-the-art Princess of Wales Conservatory opened. With the new millennium, a flourish of projects followed elsewhere; old glasshouses were restored and innovative new structures built - including the Great Glasshouse at the National Botanic Garden of Wales.

New centrepiece for Wisley

After years of planning, with various designs having been considered, at last the Society has a glasshouse befitting its status. The building work began in 2005; planting started in November last year. At full height it soars to 12m (40ft) (about the height of three double-decker buses) and internally covers 10 tennis courts in area. The building’s curvilinear design is complemented by the lake and exterior planting by designer Tom Stuart-Smith.

Further excitement is inside. The RHS Wisley tender plant collections are mostly selections and cultivars, rather than wild species. There are three climate zones, regulated by computer controls that open vents and alter moisture and shading. The temperate area is divided into two - dry and moist. In the moist area, visitors will be able to climb a winding pathway, passing behind a spectacular waterfall, to enjoy views out over planting, including Strelitzia nicolai, with huge paddle-like leaves and white bird-of-paradise flowers, elegant Roystonea regia (royal palm) and vibrant climber Bougainvillea. Living relics from the Chiswick conservatory are two huge Platycerium (stags horn fern), first moved to Wisley in 1903.

In the dry temperate area, spectacular Doryanthes palmeri (spear lily) and its spikes of scarlet flowers will jostle with succulents such as Aloe. Separated by a glass partition, the tropical zone will have a pool for aquatics, and plants such as Ficus religiosa, Cocos nucifera (coconut palm), Pandanus (screw pine) and Strongylodon macrobotrys (jade vine) will provide a profusion of variety and interest.

Education is central to the purpose of the new glasshouse; there are several ‘learning zones’, including the Clore Learning Centre, a growing lab and a teaching garden, created by garden designer Cleve West. An area called the ‘Root Zone’ will allow visitors to learn of the workings of plant roots, via museum-quality displays.
This is a new era for the RHS. Large public glasshouses are again recognised as valuable resources - rather than financial drains. Not only do they show us flora from warmer shores, they can also teach us about the natural world, something that fascinated the Victorians, and is of vital importance today.

The June issue of The Garden will look in depth at the new RHS Bicentenary Glasshouse - from internal planting layout to public access and external landscaping.

UK’s great glasshouses through the years

Phil Clayton is Features Development Editor for The Garden

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