GREENHOUSE 



GREENHOUSE 



1401 



sold at a profit above cost of production. The most 

 desirable markets are those within easy driving dis- 

 tances. If it is necessary to ship the produce to be 

 grown, electric lines will usually be found more economi- 

 cal carriers than steam Unes. A grower is nearly always 

 at a disadvantage if he has but one available road to 

 ship over. Competition insures cheaper and better 

 service. Cities with 25,000 to 50,000 poijulation are 

 often more desirable markets than much larger cities. 

 Cities which are the chief shipping-points for south- 

 ern-grown vegetables are not so good markets for 

 forcing-house products as are the cities which are not 

 60 accessible from the localities making a business of 

 growing winter vegetables for nortliern markets. 



Another matter of importance to consider in choosing 

 a forcing-house site is the cost of fuel. If natural gas 

 can be secured at a reasonable cost it is a very satis- 

 factory fuel. Coal is used most commonly as a fuel. 

 When calculating the cost of coal, the hauling of it 

 from the nearest shipping-point to the forcing-house 

 should be included. It is expensive to move large 

 quantities of coal a long distance, especially if the road 

 is not good. When a dirt road must be used, it is usually 

 best to do the hauUng in late summer rather than in 

 winter. 



While any productive soil can be made suitable for 

 forcing purposes, it is easier and cheaper to prepare a 

 sandy soil than a heavy clay soil. Other things being 

 equal, therefore, a location where the soil is a sand or 

 sandy loam is to be preferred to a clay soil. 



As large quantities of water are used in the forcing- 

 house, an abundant supply should be known to exist 

 before a site is selected for the houses. It is cheaper to 

 build and easier to operate a forcing-house on level 

 than on sloping land. A level site should, therefore, 

 be selected if possible. 



It is also an advantage to have the houses protected 

 on the sides from which the prevailing winds come. 

 Trees, hills or buildings are suitable for this purpose, 

 providing they are not near enough to shade the 

 houses much of the time. The site should not be far 

 from the dweUing, and the closer it is to the market or 

 shipping-point the better. A location which cannot be 

 satisfactorily drained or which is subject to overflow 

 should of course be avoided. 



Types of forcing-houses. 



Of the various types of forcing-houses, even-span, 

 three-quarter-span, hillside and lean-to, only two are 

 being built very generally at present. Many New 

 England growers prefer the three-quarter-span, while 

 the even-span is most popular in all other sections of 

 the country in which forcing-houses are commonly 

 erected. The three-quarter-span is used on sloping land 

 as much as the hillside type of house, or even more. 

 Good results are secured with either form. 



Form of conslruction. 



All-wood houses. — In the all-wood form of construc- 

 tion no iron is used except in the heating-plant. The 

 walls may be all wood, or wood and concrete. The posts 

 may or may not be set in concrete. The all-wood house 

 was by far the most common form of construction only 

 a few years ago and certain growers in various parts of 

 the country still prefer the all-wood houses. Red cedar 

 and cypress are the kinds of wood commonly used for 

 forcing-house erection. 



Semi-iron houses. — In the semi-iron form of construc- 

 tion all supporting posts, purlins and braces are made 

 of iron pipes or angle-iron. The walls are usually made 

 of concrete and all interior posts are set in concrete. 

 The semi-iron houses are more expensive to erect than 

 the all-wood houses but they are more durable and most 

 growers think they are cheaper in the end. 



All-iron houses. — In the all-iron construction the 

 entire framework is of iron. The various parts are put 



together in such a way that the houses are very rigid. 

 This form of construction is the most durable of all and 

 will stand a greater weight of snow and more severe 

 winds than the semi-iron or all-wood houses. The first 

 cost of the all-iron houses is from one-third to one-half 

 greater than the semi-iron construction, and this fact 

 alone stands in the way of the general use of this 

 construction. In spite of this objection, a number 

 of large all-iron houses have been erected recently 

 and they seem to be increasing in popularity, especially 

 in the eastern part of the United States. 



Trussed houses. — In the trussed form of construc- 

 tion, steel truss-rods are used to take the place of a 

 part or all of the iron or wooden posts and braces used 

 in the other forms of construction. The trussed houses 

 are very convenient to work in and very Uttle shade is 

 cast by the framework. The truss-rods are frequently 

 made to support the heating-pipes. They are also 

 convenient supports for the wires upon which the 

 cucumber and tomato vines are supported. As built in 

 the past, trussed houses have not been strong enough, in 

 all cases, to resist the weight of heavy snows and the 

 force of severe winds. Several such houses have been 

 demolished. If this defect can be eliminated this type 

 of house win be very desirable. 



Special features of forcing-house construction. 



Width of houses. — The width of the forcing-houses 

 in general use varies from 12 to 150 feet. In the East 

 the tendency is to build houses 40 to 50 feet or more in 

 width. In most parts of the West, the preference is 

 for houses from 12 to 40 feet wide. However, there 

 are individual growers in most sections of the West 

 who prefer houses over 40 feet wide. The narrower 

 houses are cheaper to build and can be kept in repair 

 more cheaply and easily than wide houses. The wider 

 houses, it is thought, can be heated more economically 

 and are better adapated to the growing of warm jilants 

 such as cucumbers and tomatoes in winter than the 

 narrower houses. 



Length of houses. — The length of forcing-houses varies 

 from 50 to 800 feet. When the gravity system of hot- 

 water heating is used the houses are seldom over 200 

 feet in length. When either steam or hot water with 

 artificial means of circulating is used, the houses may be 

 of any length up to 1,000 feet. In most forcing centers 

 the length of the houses has not exceeded 500 feet. 



Direction of houses. — Lean-to and hillside houses are 

 usually built with a southern exposure. Three-quarter- 

 span houses are generally built to run east and west 

 with the long span to the south. Even-span houses 

 are built to run north and south, east and west and in 

 some cases northeast and southwest. While there is 

 not much difference in the results secured in even-span 

 houses run either direction, there is a better distribu- 

 tion of sunlight throughout the day in houses which 

 are run north and south. 



Height of gutter. — Low gutters are almost entirely a 

 thing of the past. Modern houses are usually l)ui!t 

 with gutters at least 6 feet high and 7-feet gutters are 

 not uncommon. The outside walls of modern houses 

 are very largely of glass construction. C'onnected 

 houses are commonly built with no dividing partition 

 except in case of extreme width when an occasional 

 glass partition is put in. Some of the advantages of the 

 high gutters combined with glass in the side walls and 

 few or no dividing partitions are: greater convenience in 

 working, better circulation of air and less shading. The 

 former belief that the glass must be close to the plants, 

 for best results has been found to be erroneous. 



Pitch of roof. — The roofs of most even-span forcing- 

 houses are built with a pitch of 30° to 35°. Three- 

 quarter-span houses are usually built with the short 

 span of the roof steeper than the long span. Hillside 

 and lean-to houses are sometimes built with consider- 

 able less than a 30° pitch to the roof. 



