596 



FORCING 



tion. The plan should secure the greatest amount of 

 light, economy of space and of heating, and directness 

 and simplicity in every operation. The simple sash-bar 

 frame, without rafters (Fig. 838) is the most satisfac- 



tory when properly constructed. The side walls should 

 be low and the roof comparatively flat. Usually there 

 is no glass on the side walls. Under most conditions, 

 the house should run north and south, particularly if 

 even in span (Pig. 839), but the lay of the land and the 

 location of existing features usually determine the direc- 

 tion. If the house runs east and west, or if it stands on 

 sloping land (Pig. 840), an uneven or broken span is 

 usually advisable. The widely different opinions re- 

 specting the merits and demerits of the different spans 

 are proof that each is good under certain circumstances. 

 It is the prevail 

 ing opinion that, 

 in broken spans, 

 the long roof 

 should be to the 

 south ; yet some 

 of the best newer 

 houses have the 

 short span — 

 which is then very 

 steep— facing the 

 south (Fig. 843). 



In America, all 

 Forciug-h o u se s 

 are heated by 

 means of small 

 wrought - iron 

 pipes, which fit 

 together with 

 threaas. The old-time cast-iron flues may be employed 

 for conservatories, but they are too bimgling for Forc- 

 ing-houses. They do not admit of sufficient modification 

 in lay-out to adapt them to the long and often crooked 

 runs of Forcing-house establishments. The wrought-iron 

 pipes are heated either by steam or water. Each system 

 has its advocates, which means that each has its merits. 

 Steam is less costly to install, since less pipe is required. 

 It also admits of greater variation in the lay-out. Crooks 

 and obstacles are more easily overcome. In a large es- 

 etablishment, the place may be heated up sooner. Hot 

 water gives a milder heat because the pipes are less 



FORCING 



hot. Of itself, it is less liable to fluctuations. Theoreti- 

 cally, it is less expensive in fuel; but in practice, the 

 cost of running is found to depend more on the charac- 

 ter of the particular system and the operations of the 

 fireman than on the medium itself. When properly in- 

 stalled, steam is as uniform in action as water, and it is 

 adapted to larger areas and to higher temperatures. 



The ideal shape for a Forcing-house is probably in the 

 proportion of breadth to length as 1 is to 4 or 5. The 

 best houses are rarely less than 18 or 20 ft. wide, and 

 rarely more than 30 to 35 ft. From 400 to 500 ft. is con- 

 sidered to be the greatest profitable length. Houses of 

 greater length are now building, but they must be con- 

 sidered an experiment. Parallel houses are often 

 "nested" with good results, — the adjoining houses rest- 

 ing on a common wall. When the various houses are to 

 be used for one kind of crop, the partitions between 

 them may be omitted : a very large space may then be 

 covered with practically one house without the necessity 

 of rearing a high roof. 



The accompanying illustrations (Pigs. 838-843) show 

 various current styles of American Forcing-houses. For 

 further discussion of glass houses, see Greenhouse. 



L. H. B. 



The Winter Forcing of Vegetables. — The growing 

 of vegetables undei glass for the winter market has de- 

 veloped within the past ten years to 

 large proportions. It has grown from 

 the small compartment in private 

 houses devoted to 

 a small supply of 



641. Uneven span Forcine-house, 30 ft. wide. Hot water. 



842. Lean-to lettuce house, 26 ft. wide. Hot water. 



lettuce and radishes to entire ranges of modern houses, 

 in which are grown almost the entire list of tender vege- 

 tables. The special crops, however, are usually confined 

 to four, the management of which is here discussed, — 

 lettuce, radishes, tomatoes and cucumbers. 



The Forcing of any winter crop is a matter of princi- 

 ples rather than practice, since local conditions have 

 everything to do with the methods of culture and the 

 kinds of vegetables forced. It frequently happens that 

 the same vegetable is grown with equal success in soils 

 of widely different character by different cultivators. 

 Skill in management and close attention to details are 

 the requirements necessary to success. Two fundamen- 

 tal elements, however, are essential: heat and light. 

 The former is needed by all crops ; the latter is almost 

 imperative when fruit is wanted. With such crops as 

 lettuce, radish, rhubarb and asparagus, in which the 

 vegetative part only of the plant is wanted, bright sun- 

 light is not absolutely necessary; but with such crops as 

 tomatoes, cucumbers, melons and beans, in 

 which the fruit is the aim, no amount of heat will 

 prove a substitute for sunlight in ripen- 

 ing the pollen, which is often the criti- 

 cal factor in the results. Therefore, a 

 situation where the maximum of sun- 

 shine may be had should be selected 

 if such crops are to be grown. 



The construction of the house is not 

 a matter of the first importance. The 

 three - quarter span house perhaps 



