Laeken: City of Glass

The first part of Dr. Stephen Becker's fascinating two-parter. This explores the history of the glasshouse from Roman times...
Dr. Stephen Becker, 21 Westfield Grove, St. Johns, Wakefield, Yorks
Chamaerops No. 7, published online 23-10-2002

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Left: The Palm Tree Pavilion.
Right: Room to grow - Inside the wintergarden.

Gardeners since time immemorial have sought to manipulate the conditions of cultivation in order to accelerate plant growth, extend the growing period and improve the harvest.

Utilising the transparent rock, mica, the Romans developed greenhouses in order to provide the conditions necessary for the cultivation of plants brought from Egypt and Asia. There is evidence that some of these structures were heated.

The earliest traders and then the explorers brought back seeds, exotic fruits and flowers that had never been seen in northern Europe. The new flora aroused scientific and private interest. The knowledge rapidly accrued that they required special climatic conditions in order to flourish and that overwintering of plants required that they be protected from the cold and frost. The great scientific institutions of the time studied these plants in order to discover their utility. It became prestigious for the nobility and the wealthy to own and display foreign and exotic items in their private collections. The solution to the preservation of exotics' were various.

The smaller specimens might be placed in pots, which were taken indoors for winter. Large specimens such as citrus trees were planted in enormous tubs and kept outdoors during summer. They were overwintered in special buildings such as the Orangery. Specimens planted in the ground had wooden sheds erected around them in situ before the first frosts arrived.

Permanent houses were also built from brick and stone for all season cultivation of pineapples and citrus trees. The principal of construction was a stout north facing wall which would keep off the coldest wind but which would also act as heat exchanger, absorbing the sun's rays on warm days and releasing heat at night. The size of windows was a problem as was the maintenance of a heated environment.

Orangeries were first heated by open braziers and then by means of fires using flues. Another solution to the problem was to construct the buildings with vaulted underground chambers from which hot air circulated. Eventually there came greenhouses into which steam was directly released, followed in 1830 by the invention of the piped hot water central heating system.

Prior to 1688, man-made glass was made in blocks and sawn into layers. It contained air bubbles, which unfortunately acted as magnifying lenses and had the effect of scorching the plants behind. By 1688 glass production had improved and it was possible to make sheets by pouring it onto metal tables without the introduction of air bubbles. This enabled the construction of large windows for the admission of light into the greenhouse or orangery. The advent of industrial techniques in the nineteenth century saw a veritable explosion in the use of high-quality glass and combined with the revolutionary developments in iron manufacture, a new era came about.

The Age Of Iron

Iron which had been known since ancient times was a difficult material. It corroded easily and was unavailable in large quantities but by the end of the eighteenth century it was being used in limited quantities as a building material. But in 1783, Cort 'reverbatory' process improved pig iron by 'puddling' it and obtained a non-rusting and forgeable material. Bessemer's process allowing the manufacture of massive quantities of steel set the stage for a revolution in building techniques. Masonry was replaced. Steel and glass became the most important construction materials until the end of the nineteenth century.

The Hot House

The traditional greenhouses, stove houses and orangeries had achieved architectural elegance but had certain limitation in terms of size, space and light. It was also unfortunate that high humidity and heat was merciless in degrading wood and masonry, and took its toll. Many of the most beautiful orangeries and greenhouses Just never survived. Even the rich could not afford their colossal upkeep after the initial capital outlay. They had, however, demonstrated the practicability of enabling plants from tropical, sub-tropical and warm-temperate climates to survive the harsh north European winters.

It was not until the nineteenth century that technological sophistication enabled the construction of large steel and glass structures. Steel, glass and central heating allowed new types of buildings and a new aesthetic. Masonry was replaced in greenhouse construction. Exotic specimens requiring enormous space and with exacting light and heat requirements could now be housed in large curvilinear domes which were to assume graceful and fantastic forms, culminating in Art Deco.


Leopold II succeeded his father to the Belgian throne in 1865. He had a clear understanding of Belgium's position in Europe and the world and spent his entire energy in remedying the situation. Of all the major civil works programmes he initiated, the development of the Royal Estate at Laeken, was probably the project closest to the King's heart - part of his vision of making Belgium rich, respected and culturally advanced.

At the time of his accession, Laeken consisted of some 80 hectares. Two years later, Leopold made a decision to create a Public Park but it was not until 1876 that the plan was begun. Over the next thirty years, by various means, fair and foul, the Estate was systematically extended. Residential districts were purchased, private estates acquired or expropriated, and local council opposition quelled. So, by the time of his death in 1910, the Royal Estate occupied an enclave within a larger public park of 186 hectares.

Broad avenues linked the park with Brussels and the rest of the Belgian road network, and provided a protective cordon around the Estate enabling it to remain untouched as the rest of the city developed. The whole area was landscaped, two large lakes excavated and a reservoir dug to service the water requirements for his ambitious Greenhouses.

The Royal Greenhouses

In 1834, the first greenhouse of iron and glass was constructed in Paris for the Natural History Museum at Fleury. In the same year the Royal Botanic Gardens in Edinburgh was built. The glasshouse at Chatsworth of 1836 was with its greatly advanced heating and ventilation system to influence all subsequent greenhouse construction. The Palm House at Kew was built between 1844 and 1848. It was to inspire all that followed. In 1851, the great Crystal Palace popularised the use of iron and glass all over the world. Further advances in the iron and glass building field came with the opening of the Palmengarten in Frankfurt in 1870. This was the first large greenhouse built with no supporting members thereby allowing an unimpeded interior view.

The decision to build a winter garden at Laeken was taken in 1868 after Leopold's visit to Frankfurt, and having learned of the intention to build a Palmengarten there.

City Of Glass

The King enlisted the services of the architect, Alphonse Balat. By 1874, the first sketches had been drafted and in July, the construction of the frame of the Winter Garden was started, and completed in 1875. In 1876, the dome was covered with glass. The heating system was installed and became operational by March 1879. In the bitter winter that followed, temperatures fell to 32°C, but the temperature within remained satisfactory thus allowing the structure to be planted the following year.

Whilst the colossal Winter Garden was built, the Orangery was enlarged, and the Camelia House, Dining Room Greenhouse and Theatre Greenhouse were constructed, as well as the connecting glass walkways.

In 1880, the Palm Tree Pavilion was built, two large lakes excavated and a reservoir for the greenhouses. In addition, a water catchment station was added in 1885 as well as two large and two small cultivation greenhouses. One of the large ones is now the Azalea House.

Leopold became head of the Congo Free State in 1885, and in order to houseplants from Africa had the large Congo Greenhouse constructed the following year at the same time as the Embarcadero. An electricity station allowing electric lighting followed. During 1890 the Royal Palace underwent extensive renovation following a fire, and undeterred, work commenced on the Palm Tree Plateau, comprising the Pavilion, the Palm House and the Debarcadere. The Iron Church, also of iron and glass, was added later. The City of Glass was completed in 1895.

Well, that's the history lesson over. In the next edition we take a trip to Laeken and spend several happy pages exploring The City of Glass - a dazzling and unforgettable experience. Don't miss it!

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