CHAPTER IX 



THE USE OF GLASS IN VEGETABLE GROWING 



Vegetable plants for early transplanting are usually started 

 under glass. Glass is also used for growing certain crops to 

 maturity outside their normal season, and in certain sections for 

 wintering over plants started in the autumn. There are three 

 kinds of glass structures that may be used in vegetable growing: 

 Coldframes, hotbeds and greenhouses. 



A coldframe is the simplest form of glass structure and consists 

 essentially of a wooden frame covered with glass sash. It depends 

 solely upon the sun for its source of heat, and upon the protection 

 of the glass and additional covering to prevent too rapid radiation 

 of the heat at night. It is impossible to make a coldframe very 

 warm in cold weather. Its usefulness is therefore limited to rela- 

 tively mild climates, the growing of cool-season crops, the starting 

 of plants for rather late transplanting, or the hardening-off of 

 plants started in greenhouses and hotbeds. Its principal use in 

 general vegetable growing at the North is for hardening-off plants 

 preparatory to transplanting, and for this purpose it has no equal. 

 Sometimes, for the sake of cheapness, cloth is substituted for glass 

 as a cover for coldframes (Fig. 32), but this limits their use to 

 still warmer w^eather than when glass is employed. 



A hotbed is very much like a coldframe except that it is sup- 

 plied with heat in addition to that furnished directly by the sun. 

 The most common source of heat for hotbeds is fermenting horse 

 manure placed under the soil of the bed. Other hotbeds are heated 

 through flues by means of wood or coal fires. Occasionally a bed 

 is heated by steam or hot water through pipes connected with the 

 heating system of a greenhouse or residence. 



Hotbeds are superior to coldframes for starting early plants 

 because they can be operated in colder weather. At the North 

 it is impossible to grow really early tomato, pepper, or egg plants 

 by the use of coldframes alone, for these plants demand higher 

 temperatures than can be maintained in a coldframe at the time 

 they must be started. Fire hotbeds have an advantage over 

 manure hotbeds, since they can be started in colder weather and 

 the heat controlled much more completely. 

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