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Greenhouse

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For other uses, see Greenhouse (disambiguation)

Image:Botanischer Garten BS.Seerosen.jpg

A greenhouse (also called a glasshouse or hothouse) is a building where plants are cultivated.

1 Explanation
2 Uses
3 History
4 References
5 See also
6 External links

[edit] Explanation

Main article: solar greenhouse (technical)

A greenhouse is built of glass or plastic; it heats up because the sun's incoming ultraviolet radiation warms plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. The glass used for a greenhouse works as a selective transmission medium for different spectral frequencies, and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. This warms the air near the ground, and this air is prevented from rising and flowing away, in addition to the fact that infrared radiation cannot pass through the greenhouse glass. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. Greenhouses thus work by trapping electromagnetic radiation and preventing convection.

[edit] Uses

Greenhouse effects are often used for growing flowers, vegetables, fruits, and tobacco plants. Bumblebees are the pollinators of choice for most greenhouse pollination, although other types of bees have been used, as well as artificial pollination.

Mowing young tobacco in greenhouse of half million plants (Hemingway, South Carolina)

Besides tobacco, many vegetables and flowers are grown in greenhouses in late winter and early spring, then transplanted outside as the weather warms. Started plants are usually available for gardeners in farmers' markets at transplanting time.

The closed environment of a greenhouse has its own unique requirements, compared with outdoor production. Pests and diseases, and extremes of heat and humidity, have to be controlled, and irrigation is necessary to provide water. Significant inputs of heat and light may be required, particularly with winter production of warm-weather vegetables. Special greenhouse varieties of certain crops, like tomatoes, are generally used for commercial production.

Greenhouses are increasingly important in the food supply of high latitude countries. The largest greenhouse complex in the world is at Leamington, Ontario (close to Canada's most southern point) where about 200 acres (0.8 km²) of tomatoes are entirely grown under glass.

Greenhouses protect crops from too much heat or cold, shield plants from dust storms and blizzards, and help to keep out pests. Light and temperature control allows greenhouses to turn unarable land into arable land. Greenhouses can feed starving nations where crops can't survive in the harsh deserts and arctic wastes. Hydroponics can be used in greenhouses as well to make the most use of the interior space.

Biologist John Todd invented a greenhouse that turns sewage into water, through the natural processes of bacteria, plants, and animals.

[edit] History

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The idea of growing plants in environmentally controlled areas has been around for a long time. Doctors for the Roman emperor Tiberius prescribed a cucumber a day for him. The Roman gardeners used artificial methods (similar to the greenhouse system) of growing to have it available for his table every day of the year. Cucumbers were planted in wheeled carts which were put in the sun daily, then taken inside to keep them warm at night. The cucumbers were stored under frames or in cucumber houses glazed with either oiled cloth known as "specularia" or with sheets of mica. (Pliny the Elder and Columella).

The first modern greenhouses were built in Italy in the Sixteenth Century to house the exotic plants that explorers were bringing back from the tropics. They were originally called giardini botanici (botanical gardens). The concept of greenhouses soon spread to Holland and then England, along with the plants. Some of these early attempts required enormous work to close up at night, or to winterize. There were serious problems with providing adequate and balanced heat in these early greenhouses.

Jules Charles, a French botanist, is often credited with building the first practical modern greenhouse in Leiden, Holland to grow medicinal tropical plants.

Originally on the estates of the rich, with the growth of the science of botany greenhouses spread to the universities. The British some times called their greenhouses conservatories, since they conserved the plants. The French called their first greenhouses orangeries, since they were used to protect orange trees from freezing. As pineapples became popular pineries were built. Experimentation with the design of greenhouses continued during the Seventeenth Century in Europe as technology produced better glass and construction techniques improved. The greenhouse at the Palace of Versailles was an example of their size and elaborateness; it was more than 500 feet long, 42 feet wide, and 45 feet high.

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In the Eighteenth Century the largest greenhouses were built. The conservatory at Kew Gardens in England is a prime example of the Victorian greenhouse. Although intended for both horticultural and non-horticultural exhibition these included London's Crystal Palace, the New York Crystal Palace and Munich’s Glaspalast. Joseph Paxton, who had experimented with glass and iron in the creation of large greenhouses as the head gardener at Chatsworth, in Derbyshire, working for the Duke of Devonshire, designed and built the first, London's Crystal Palace.

In Japan, the first greenhouse was built in 1880 by Samuel Cocking, a British merchant who exported herbs.

In the Twentieth Century the geodesic dome was added to the many types of greenhouses.

[edit] References

Woods, May (1988)Glass houses: history of greenhouses, orangeries and conservatories Aurum Press, London, ISBN 0906053854 ;
Cunningham, Anne S. (2000) Crystal palaces : garden conservatories of the United States Princeton Architectural Press, New York, ISBN 1568982429 ;
Vleeschouwer, Olivier de (2001) Greenhouses and conservatories Flammarion, Paris, ISBN 208010585X ;
Lemmon, Kenneth (1963) The covered garden Dufour, Philadelphia;
Muijzenberg, Erwin W B van den (1980) A history of greenhouses Institute for Agricultural Engineering, Wageningen, Netherlands;
Enoshima Jinja Shrine Botanical Garden