CHAPTER IV 



FORCING AND FORCING STRUCTURES 



Definition of forcing. The term " forcing," as used in horti- 

 culture, means growing plants out of season. Artificial conditions 

 produced during the winter for the purpose of imitating the condi- 

 tions under which tropical plants normally grow cannot be consid- 

 ered forcing ; but when such crops as lettuce, cucumbers, radishes, 

 and tomatoes are grown out of their normal season and environ- 

 ment, the crop is then being forced. The forcing industry is seldom 

 made a special line of work by market gardeners ; as a rule it is an 

 adjunct to floriculture, truck farming, or market gardening, usually 

 the last. The industry is confined to comparatively few crops and 

 to those sections where severe winter conditions prevail and where 

 extensive markets which will take a high-priced product are acces- 

 sible. One of the most important forcing centers of the United 

 States is in the immediate vicinity of Boston. 



Crops which are forced. The vegetables most often forced are : 

 (i) lettuce ; (2) tomatoes ; (3) cucumbers ; (4) radishes ; (5) cauli- 

 flower ; and (6) beans. Slight attention is given to muskmelons 

 and eggplants, and still less to asparagus and rhubarb. The forcing 

 of mushrooms is of considerable importance in America, where 

 climatic conditions do not admit of growing them successfully in 

 the open. To meet the needs of the forcing industry special vari- 

 eties have been developed which thrive well when grown in a 

 forcing house, but which are not adapted to out-door conditions 

 even in this country. 



Since the operations carried on in a forcing house are neces- 

 sarily limited in extent, they must be made as intensive as possible ; 

 that is, the greatest quantity of product as well as the maximum 

 number of crops must be secured from a given area in the shortest 

 possible time. It is not feasible at this point to give specific 

 cultural directions for the handling of the various crops which are 

 grown in forcing structures, but this subject will be considered 



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