Provision must be made for ample ventilation. The most approved plan is to have a line of vents on both sides of the ridge. If devices are used to prevent the ventilating sash from binding, there is no reason why they should not be continuous. If such devices are not used, at least one line of glass should separate the ventilators. They may be hinged on the ridge or on the headers of the roof bars. Both systems have earnest advocates. The ventilation is more free when the sash are hinged on the headers, opening at the ridge; while there is, on the other hand, greater danger of cold drafts striking the plants, and rain and snow are easily admitted with this form of ventilation. But when houses are used until midsummer or later, hinging on the header is probably the better plan. Side ventilators are often provided, but many growers regard them as of doubtful utility. They are most useful in warm weather. But whatever the method of ventilation, it is of the greatest importance that the ventilating machinery work easily.
A few years ago greenhouse growers thought it essential to provide benches with bottom heat for practically all greenhouse crops, but the opinions held today are different. In many of the largest and most successful houses there are no benches or even beds with board, brick or concrete sides. These mammoth houses often have large doors at the ends so a horse and cart can enter with manure or other supplies. It is also possible to use plow and harrow in the preparation of the soil for planting. While all greenhouse growers do not approve of horse tillage under glass, some of the most successful growers always use horse implements in preparing ground for the fall crop.
Benches are convenient in the handling of flats and potted plants, but they are expensive to construct and maintain unless made of concrete.
Solid beds, with or without sides, provide more uniform soil conditions than do shallow beds. There is less danger of injury from improper watering and, therefore, the chances of success are increased. Solid beds are especially advantageous when the watering must be intrusted to men of limited experience.
The walks should be arranged so that all the beds can be cared for conveniently. Beds or benches 5 feet wide and walks or alleys 18 inches in width make a desirable combination, although the relative width of beds in commercial houses is often much greater. As plants do not do well next to the walls, it is desirable to have walks there, and the house space can then be divided in such a manner as may seem convenient for the care and harvesting of the crops to be grown.
Hot water is unquestionably the best system for heating small houses, and there are many arguments in its favor for large ranges of houses. If pumps or a pressure system are used to secure rapid circulation, the radiating surface need not be much greater than in a steam system. The higher cost of installation has always been one of the greatest objections to hot water. With the pressure system instead of the open tank, the water is heated to a higher temperature and also made to circulate more rapidly.
The advantages of hot water over steam may be stated as follows: (1) As the hot water in the pipes retains heat for a greater length of time, the boiler may be left for a longer time without attention. This is a great advantage in small greenhouses, where it would not pay to employ a night fireman. (2) Less fuel is consumed. (3) Proper conditions of moisture are maintained with less difficulty. Other advantages are often stated, but the foregoing are the most important. It is not so expensive, however, to install a steam plant nor so troublesome to make repairs.
Formerly, 4-inch cast iron pipe was used extensively and rust joints were in common use. Wrought iron pipe is now generally employed, and it is always threaded - an advantage that makes installation more rapid and provides joints which are not so likely to leak. Most frequently 1« and 2-inch pipe is used for the coils in hot water heating and 1¬-inch pipe for steam heating, connecting with mains of proper size. Whatever the system, the pipe should be placed with the greatest care, observing the principles of the method of heating to be used.
The boiler should be of ample capacity to maintain proper temperatures; forcing a boiler means a waste of fuel, and the boiler itself will not last so long. There are several types of boilers on the market. The most important point to consider in selecting a boiler is to see that the construction is of such a type that the greatest heat will be realized from the fuel consumed. The flames should strike the sections of the boiler at right angles, and the connection with the smoke pipe should not be too direct. Sectional and tubular boilers are in most common use in greenhouse heating.
In every greenhouse establishment there is a great deal of work to be done in the way of seed sowing, transplanting, potting and preparing crops for market. Nothing is more important than a commodious room where all the work can be done in perfect comfort. This room should be well lighted and properly heated and ventilated. Tables of the right height are necessary, and a small room for tools will be found very convenient.