Greenhouse

For other uses, see Greenhouse (disambiguation)

Greenhouse. In America the word greenhouse is used generically for any glass building in which plants are grown, with the exception of coldframes and hotbeds. Originally and etymologically, however, it means a house in which plants are kept alive or green: in the greenhouse plants are placed for winter protection, and it is not expected that they shall grow. The evolution of the true greenhouse seems to have begun with the idea of a human dwelling-house. At first larger windows were inserted; and later, a glass roof was added. In early times it was thought best to have living-rooms above the greenhouse, that it might not freeze through the roof. Even as late as 1806, Bernard M. Mahon, writing in Philadelphia, felt called upon to combat this idea. The old or original conception of a greenhouse as a place for protecting and storing plants is practically extinct, at least in America (Fig. 1749). In England, the word greenhouse is mostly used for a house or structure in which are kept or grown those plants that do not require a very high temperature.

Other types of plant-houses are the conservatory (which see), in which plants are kept for display; the forcing-house (see Forcing), in which plants are forced to grow at other times than their normal season; the stove or warmhouse; the propagating-pit. Originally the warmest part of the plant-house, that part in which tropical plants were grown, was heated by a stove made of brick, and the house itself came to be called a stove. This use of the word stove to designate the warmest part or room of the range is general in England, but in America we prefer the word warmhouse (and this word is much used in this Cyclopedia). Originally, hothouse was practically equivalent to stove, but this term is little used in this country, and when used it is mostly applied generically in the sense of greenhouse.

It will thus be seen that there is no one word that is properly generic for all glass plant-houses. The word glasshouse has been suggested, and it is often used in this work; but there are other glass houses than those used for plants. It seems best, therefore, to use the word greenhouse for all glass buildings in which plants are grown; and American usage favors this conclusion.

The long, low greenhouse range, of the type we now know in our commercial establishments, probably had a different origin from the high-sided greenhouse. The glasshouse range appears to have developed from the practice of protecting fruits and other plants against a wall. In European countries, particularly in England, it is the practice to train fruits and other plants on stone or brick walls, that they may be protected from inclement weather and receive the greater sun heat that is stored in the masonry. It occurred to Nicholas Facio Duilhier to incline these fruit walls to the horizon so that they would receive the greater part of the incident rays of the sun at right angles. He wrote a book on the subject of "Fruit-Walls Improved," which was published in England in 1699. Facio was a mathematician, and he worked out the principle of the inclined walls from mathematical considerations. Such walls were actually built, but according to the testimony of Stephen Switzer, who wrote in 1724, these walls were not more successful than those which stood perpendicularly. Certain of these walls on the grounds of Belvoir Castle, and over which grapes were growing, received the additional protection of glass sash set in front of the inclined walls and over the vines. In addition to this, flues were constructed behind the wall in which heat might be supplied. The construction of hollow heated walls was not uncommon in that day. The satisfactory results that followed this experiment induced Switzer to design glass-covered walls. The "glasshouse" which he pictured in the "Practical Fruit-Gardener" (1731) represents a greenhouse 3 ½ feet wide in the clear (Fig. 1750). At the back of this house is an inclined heated wall on which the grapes are grown. Three and one-half feet in front of this a framework is erected to receive the sash. There are three tiers of openings or windows along the front, the two lower ones of which are for window-sash, and the upper one is vacant in order to provide for ventilation and to allow space to receive the lower sash when they are lifted up. The whole structure is covered with a roof or coping. Switzer declares that the introduction of these covered sloping walls "led the world" to the "improvement of glassing and forcing grapes, which was never done to that Perfection in any Place as it is upon some of the great Slopes of that elevated and noble Situation of Belvoir Castle." Johnson, in his "History of English Gardening," quotes the remarks of Switzer, and makes the statement that the use of these walls "led to the first erection of a regular forcing structure of which we have an account." The immediate outcome of these covered walls seems to have been the lean-to greenhouse, and from that structure has perhaps developed the double-span glass range of the present day. Long before Switzer's time plants were forced in a crude way, even by the Romans, mostly by being placed in baskets or other movable receptacles, so that they could be placed under cover in inclement weather; but the improvements of Facio and Switzer seem to have been among the earliest attempts in England to make low glass ranges for plants.

It was about the beginning of the nineteenth century that great improvements began to be made in the glasshouse. This new interest was due to the introduction of new plants from strange countries, the improvement of heating apparatus, and the general advance in the art of the building. The ideals that prevailed in the opening of the century may be gleaned from J. Loudon’s “Treatise on Several Improvements in Hot-Houses” in London, 1805. One of the devices recommended by Loudon will interest the reader. It is shown in Fig. 1751. The bellows is used for the purpose of forcing air into the house, so the plants may be supplied with a fresh or nonvitiated atmosphere. “By forcing the air into the house, once a day or so, doubles the quantity of air which the house usually contains" can besecured. The house could be "charged." The tube leading from the bellows is shown at b; it discharges at c. Curtains run on wire, i; the curtain cord is at f.

Greenhouses are now built on the plan of the long low glass range with sides varying from 5 feet 6 inches to 7 feet in height. The tendency in commercial structures is for a height of 7 feet from ground to eaves. The taller glass structures are used for conservatory purposes, housing such table plants as palms, tree- ferns, or the like, or when an architectural feature is desired. The general tendency of the building of glass structures is toward extreme simplicity (Fig. 1547, p. 1256). In the extreme South, lattice-work buildings are sometimes used for the protection of plants, both from light frosts and from the sun (Fig. 1752). The heating now employed in this country is of three different kinds: hot water under very low pressure or in the open-tank system; hot water in practically closed circuits; and steam. Hot water under low pressure is an old-time mode of heating, and is not now popular in this country except for conservatories and private establishments. The heavy cumbersome pipes are not adapted to laying over long distances and under varying conditions. The commercial houses are now heated by means of wrought-iron pipes, which go together with threads. The comparative merits of steam and hot water in these wrought-iron pipes are much discussed. For large establishments, hot water under pressure is now employed to some extent. Much progress has been made in methods of heating in recent years, and either steam or hot water gives good results when competently installed. The merits of one system or the other are very largely those of the individual establishment and apparatus, and the personal choice of the operator (see page 1403; also pages 1400 and 1402).

The simple straight and direct house is now much in favor with the commercial growers of carnations, chrysanthemums, violets, roses, vegetables, and with propagators. Most of the greenhouse construction firms are designing houses most admirably adapted to the growing of these plants. Each firm has a few original forms worked into the detail plans, calculated to appeal to the growers' fancy. Perhaps the ideal structure for carnations, for example, is a single detached house, about 50 feet wide and 500 feet or less in length, with ventilators on each side of the ridge and on each side below the eaves, and the eaves, or the gutters, 6 feet above the grade.

The Royal Greenhouses of Laeken. A masterpiece of 19th-century greenhouse architecture

A greenhouse in Saint Paul, Minnesota.

Nymphaea at the botanical Garden in Braunschweig, Germany

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

Explanation

Main article: solar greenhouse (technical)

A greenhouse is a structure with a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming solar radiation from the sun 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. These structures range in size from small sheds to very large buildings.

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. 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. Miniature greenhouses are known as a cold frame.

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 in Willcox, Arizona, USA where 262 acres of tomatoes and cucumbers 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.

Backyard hobby greenhouse use has increased dramatically in the United States in the past decade. Companies such as Rion, Solexx and Juliana have introduced entire lines of backyard greenhouses for use by the hobby gardener. Major retail establishments as well as small niche players sell hobby greenhouses primarily over the internet. Backyard hobby greenhouse use is still more popular in Europe and England, however.

History

19th Century Orangerie in Weilburg, Germany

Victorian conservatory, Kew Gardens

A modern glasshouse in RHS Wisley

The idea of growing plants in environmentally controlled areas has existed since Roman times. Doctors for the Roman emperor Tiberius prescribed him a cucumber daily. 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 brought back from the tropics. They were originally called giardini botanici (botanical gardens). The concept of greenhouses soon spread to the Netherlands and then England, along with the plants. Some of these early attempts required enormous amounts of 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, or pineapple pits, 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.

In the nineteenth 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. A major architectural achievement in monumental greenhouse building were the Royal Greenhouses of Laeken (1874-1895) for King Leopold II of Belgium.

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.

References

• Woods, May (1988)Glass houses: history of greenhouses, orangeries and conservatories Aurum Press, London, ISBN 0-906053-85-4 ;
• Cunningham, Anne S. (2000) Crystal palaces : garden conservatories of the United States Princeton Architectural Press, New York, ISBN 1-56898-242-9 ;
• Vleeschouwer, Olivier de (2001) Greenhouses and conservatories Flammarion, Paris, ISBN 2-08-010585-X ;
• 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

See also

• Conservatory (greenhouse)
• Solar greenhouse (technical)
• Olcott Park Greenhouse
• Greenhouse effect
• Lord & Burnham (greenhouse manufacturers)
• Royal Greenhouses of Laeken in Belgium

External links

• Planning and Building a Greenhouse
• North Carolina State University Greenhouse Food Production website
• Organic Greenhouse Tomato Production
• Mini Greenhouses