GREENHOUSES AND FRAMES 223 



practically no cutting will have to be 



done in building the frame. Let the 



sides come down well below the ground 



as the soil inside should be a few inches 



below the general ground level. After 



it is finished, a layer of gravel or 



roofing slate on the outside, or banking 



up with soil, nearly to the top, will 



greatly increase its efficiency in keeping small forcing frame 



out cold. Concrete frames should 



be made 4 to 6 in. thick and sunk 



well below the ground level so that the frost cannot get under the mason 



work. 



At least part of your sash should be of the double glazed type. Two 

 layers of glass instead of one are used, with the result that the thin 

 air space left between them forms a cushion of dead air which is as 

 effective as a blanket of wool or canvas in keeping out the cold, while 

 it admits the light and sunshine as readily as a single layer of glass. 

 With a good tight frame and double glass sash, crops may be grown 

 well into the Winter, and started very early in the Spring, without any 

 other protection. 



With single glass sash, wooden shutters or burlap mats are used as 

 an extra covering in cold weather. If these are employed in addition to 

 double glass sash, half hardy crops, such as Lettuce, can be carried 

 through very severe weather without any artificial heat at all, and the 

 frames will be ready for use in the Spring as early as they may be 

 wanted, without having to wait for them to thaw out. 



Hot beds are made one to two feet deeper than for cold frames to 

 allow for the layer of manure put in to furnish the heat. 



LOCATION. Generally it is best to locate with southern exposure 

 and with a protection of trees or fence at north (see p. 199). Three feet 

 should be allowed back of frame to the fence to allow for working facili- 

 ties. Do not put the frame where the Spring rains may drain into it; 

 good drainage is especially important in Winter as well as in Spring. 



PREPARATION OF BED. During Winter keep the snow out by 

 a covering of boards. In the middle of March, or six or eight weeks 

 before plants can be safely put out of doors, if the bed has been con- 

 structed as directed, two feet of fresh manure is placed in the frames. 

 Nothing but fresh manure will suffice, horse manure being best, which 

 has been piled and turned several times to bring to a uniform tem- 

 perature. As placed in frames, the manure should gradually be 

 stamped rather firmly. To insure more uniform heating a layer of 

 straw is used to cover the manure. Soil which has been stored in 



