GLASSHOUSES FOR VEGETABLE CROPS For many years gardeners made use of cold frames and hotbeds for the starting of vegetable plants in the spring, and for the forcing of lettuce and radishes, to get them on the market before they could be produced in the open air. A de mand soon sprang up for a great variety of other vegetables, and it was found that, if they could be produced throughout the winter months, the prices they would bring would be sufficiently remunerative to make their culture very profit able. This has led to the erection of numerous forms of vegetable forcing-houses, and some of the ranges are so extensive as to cover several acres. Some of the larger houses are several hundred feet in length and fifty to one hundred feet in width, and are so arranged as to permit teams to be driven through to bring in soil and manure; and horses are often used for plowing and working the ground. The modern vegetable forcing-house makes it possible to produce crops of all kinds of vegetables with comparatively little risk, and with far less labor and expense than was possible with hotbeds or coldframes or with the form of greenhouses used in the early days.
The business of growing vegetable plants either for sale or home use has assumed large proportions.
In some cases, the houses that have been used for the growing of vegetables or flowers are used for this purpose, while in others spe cial houses are used. Although not necessary, it will be convenient to have raised benches in houses to be used for this purpose, at least enough to serve as seedbeds, other wise the vegeta ble houses will answer very well.
Less care is re quired in the con-..
struction of houses to be used exclusively f or the starting of plants in the spring. The roof covering of small houses can be of hotbed sash, and the houses can be heated by means of flues.
Types of houses.
The forcing-houses in use thirty years ago, and which are occasionally found today, were about ten feet in width, with wooden walls and the roof covered with a row of hotbed sash on each side of the ridge. They were commonly heated with a flue.
The width of the houses was gradually increased to about twenty feet. (Fig. 179.) The walls were either of posts covered with a double thickness of boards, or there was a row of glass one to two feet in width under the plates to furnish light and ventilation. In addition to the two benches about four feet wide found in narrow houses, these contained a bed or bench through the center about eight feet wide. While some of the houses of this size were heated with flues, hot water was more commonly used, although in large ranges steam was generally preferred. This width and style of house gives good satisfaction, and even today will be found very well suited to the pur pose if only one or two small houses are required.
The modern vegetable forcing-houses are more commonly constructed of widths varying from twenty-six to fifty or more feet, as it has been found that better crops can be grown in the wide houses and there will be less waste room. By building the houses where there is a slight gradual slope of the land toward the south, it is possible to erect a house forty or fifty feet in width without having the ridge excessively high, while the k amount of space lost along the south wall will be much less than when three to five houses are required to give the same area. (Fig. 180.) In addition to the ordinary form of greenhouse with vertical walls, a style that will add eight to ten feet to the available width of the house, without greatly increas ing the cost of construction or of heating, is built with a sort of hip roof ; that is, in stead of having vertical walls, the plates are sup ported by means of iron posts and the side walls stand at an angle so that at the ground the walls are three to five feet outside of the plates on each side of the house.
If the houses are not sufficiently large to make it worth while to drive in at the ends with compost, there should be either ventilators or movable sash in the side walls that can be taken out so that soil can be thrown in.