CHAPTER 4 

 VEGETABLE FORCING 



BY C. W. WAID 



Extension Specialist, Michigan Agricultural College 



Vegetable forcing is a term applied to the growing of vegetables in 

 such a way that they mature or become suitable for use in a shorter time 

 or at a different season than when grown under normal conditions. Cold- 

 frames, hotbeds and greenhouses are used for this purpose. 



Cold-Frames. Cold-frames are wooden or concrete structures covered 

 with glass or cloth. They are entirely dependent upon the sun's rays as 

 the source of heat and serve as a protection against cold winds and too 

 rapid radiation of the heat at night. The frames are usually built to run 

 east and west with the south side about a foot above the surface of the 

 ground and the north side a foot or so higher than the south side. They 

 are about six feet in width and of any desired length. When glass is used 

 as a cover the panes are fastened in sash. The standard size of the sash is 

 three by six feet. 



It is not possible to maintain a uniform temperature in cold-frames 

 during very cold weather. Their use is, therefore, confined to relatively 

 mild climates or to short periods in the colder climates. They are best 

 adapted to the growing of cool-season crops, the starting of plants for late 

 transplanting or the hardening off of plants started earlier in the greenhouse 

 or hotbed. A cloth cover is sometimes used in the place of glass as a matter 

 of economy. 



Hotbeds. Hotbeds are similar in construction to cold-frames. The 

 chief difference is that in addition to the heat secured from the sun's rays 

 other means are used to supply heat in the hotbeds. The common source 

 of artificial heat is fermented horse manure. Hot-air flues and steam or 

 hot-water pipes are also used for this purpose. When steam or hot water 

 is used to heat a greenhouse or residence the same system can be used to 

 advantage in heating the hotbeds. Hotbeds are more satisfactory than 

 cold-frames for the growing of early crops or the starting of early plants in 

 a cold climate, as the temperature can be made more uniform. 



To prepare a manure hotbed, the dirt is removed from inside the frame 

 to a depth of from one and one-half to two and one-half feet. Horse manure 

 from grain-fed animals should be placed in a compact pile at least three 

 weeks before it is to be put in the pit. As soon as the manure begins to 

 ferment it should be forked over and thoroughly mixed. All lumps should 

 be broken. A second forking over may be needed before it is ready for the 



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