1402 



GREENHOUSE 



GREENHOUSE 



Gla'ss and glazing. — Nothing but "A" quality glass 

 is used in modern forcing-houses. Single-strength has 

 been almost entirely replaced by double-strength 

 glass. The standard size is 16- by 24-inch glass. It is 

 usually laid the narrow way, although in sections of the 

 country in which the snowfall is light the glass is fre- 

 quently laid the 2-i-inch way. Twenty- by 24-inch 

 glass is used by some growers. Butted glass was 

 popular for a time and is yet with some growers, but 

 lapped glass is most commonly used at the present 

 time. When lapped, the glass is imbedded in putty 

 and secured in place by the use of glazing-points. 

 Butted glass is held in place by grooved strips of wood 

 placed over the edges and fastened to the sash-bars 

 with screws. 



Ve7itilation. — An abundance of ventilation should 

 always be provided, as the health of the plants is 

 governed to a considerable extent by the ventilation 

 given or not given at the proper time. When the narrow 

 ridge-and-furrow type of forcing-house is used, provision 

 is made for ventilators on only one side of the roof. If 

 the houses are 30 or more feet in width, ventilators are 

 usually placed on both sides of the ridge. In some 

 cases, the ventilators are continuous, but owing to the 

 Labihty of binding when .so built most growers use 

 separate ventilator sash. The sash are separated from 

 each other by one or two hnes of fixed glass. They are 

 hinged on the ridge or on the header at the lower edge 

 of the sash. When they are hinged on the header and 

 open at the ridge the ventilation is more free, but cold 

 draughts of air and rain or snow are more Uable to 

 enter than when the sash are hinged at the ridge and 

 open at the lower edge. Side ventilators are a decided 

 advantage in warm weather. When they are not pro- 

 vided, the air in the houses often becomes stale and 

 oppressive. In such a condition it is unsuitable for 

 normal plant-growth and unpleasant for those who are 

 obUged to inhale it. Easy-working ventilator machinery 

 should be provided for the ventilators both on the 

 sides and roofs. 



Heating. — For small forcing-houses, hot water is 

 undoubtedly the most satisfactory method of heating. 

 Some of the advantages of hot water over steam heat 

 are: No night fireman is needed in small forcing-houses 

 as the fire can be left for several hours without atten- 

 tion. Less fuel is required, especially in mild weather. 

 The proper amount of moisture in the air can be main- 

 tained more easily. The heating-pipes if kept filled 

 with water will outlast steam-heated pipes. The chief 

 advantage of the steam heat over hot water is that it 

 is cheaper to install. The reason for this is that when 

 gravity is the means of circulating the water, larger 

 pipes are required for properly heating the houses with 

 water than are necessary where steam is the heat used. 

 The gravity system is the principal method used in 

 small hot-water-heated houses. Another advantage of 

 steam over hot water is that the heat can be regulated 

 more easily. When steam sterilization is practised it is 

 an advantage to be able to use the same boilers for this 

 purpose as are used for heating the houses. While a 

 larger part of the large ranges of houses are heated with 

 steam, some of the largest are heated with hot water. 

 A ten-acre range of houses near Toledo, Ohio, is heated 

 with hot water which is pumped through 1 J 4-inch 

 heating-pipes. The houses are 700 feet long and cover 

 a width of over 600 feet. There is but one heating- 

 plant and it is located at the center of one side of the 

 range. The heating-pipes are close to the ground and 

 are nearly level from one end of the houses to the other. 

 The water is pumped through the entire length of 

 pipes in a very few minutes. The installation of this 

 hot-water heating-plant cost httle if any more than a 

 steam heating-plant would have cost and it can be 

 operated more cheaply than a steam plant which would 

 be large enough to heat a range of houses of the same 

 size. 



Heating-pipes. — Practically all pipes used for heat- 

 ing purposes at the present time are of wrought-iron. 

 They are threaded and can be united by screwing them 

 into connections made for the purpose. This method 

 of connecting furnishes a tight joint and can be easily 

 put together. Two-inch pipes are used as a rule for 

 hot-water heating with gravity means of circulating. 

 For hot water with forced circulation and for steam, 

 IJi'-inch pipes are generally considered the best size 

 to use. 



Benches vs. beds. — In nearly all vegetable-forcing 

 centers, except Chicago, raised benches are no longer 

 used except by an occasional grower. The cost of 

 building the benches is so gi-eat that most growers think 

 the added cost more than offsets the advantages of the 

 benches over the beds. Cement benches when arranged 

 for sub-irrigation are very satisfactory. They are 

 especially desirable for lettuce and tomatoes. Sur- 

 face-watered benches are not nearly so satisfactory 

 for these crops as sub-irrigated benches. Ground beds 

 are frequently made with concrete sides but the more 

 recent plan is to have nothing but narrow concrete 

 walks to separate one bed from another. 



Service room. — One of the features which goes with 

 an up-to-date vegetable-forcing plant is a conveniently 

 arranged and well-lighted service room. Provision 

 should be made for washing vegetables and for other 

 operations which go with a proper preparation of the 

 vegetables for the market. 



Plant-house. — Another important adjunct to a modern 

 forcing-house is a plantr-house which is independent 

 of the other part of the range so far as the heating 

 of it is concerned. To grow young plants successfully, 

 especially warm plants such as cucumbers and tomatoes, 

 it is important to be able to provide the proper tempera- 

 ture for each kind of plant. This can be done to best 

 advantage if the plants can be grown in a plant-house 

 built especially for that purpose. c w, Waid. 



Greenhouse glass. 



The selection of glass for greenhouses, and the nature 

 of the imperfections which render it undesirable for 

 such use, are questions which have received much 

 attention from horticultural WTiters, and which have 

 brought forth a variety of answers. Three qualities 

 are essential in all gla.ss to be used in greenhouse con- 

 struction: first, minimum of obstruction to solar rays; 

 second, strength sufficient to withstand the strain of 

 winds and storms, especially hail; and third, freedom 

 from defects that render it liable to burn plants grown 

 under it. 



It is an estabhshed fact 

 that plants thrive best 

 under a clear and trans- 

 parent glass, which lets 

 tlu^ough the greatest pos- 

 sible percentage of the 

 Sim's rays. This includes 

 all the solar rays, calorific 

 or heat rays, and actinic 

 or chemical rays, as well 

 as the colorific or light 

 rays. Clear white glass of 

 the grade known as "single 

 thick" (twelve panes to 

 the inch) lets through 

 from 60 to 70 per cent of 

 the sun's rays; common 

 green glass of the same 

 thickness, 52 to 56 per 

 cent, and "double thick" 

 (eight panes to the inch) 

 common green glass, from 

 1759. Burned areas on a 50 to .52 per cent. This 



begonia leaf. percentage is reduced by 



