LETTUCE 281 



seldom done unless the sash are required for protecting some 

 other crop. About Baltimore, Washington, and Norfolk, lettuce 

 can be successfully wintered and brought to maturity in sash- 

 covered frames in time to allow the same sash to be used for the 

 protection of a frame crop of cucumbers. Such a system of crop- 

 ping is very remunerative, for both a fall and a spring crop of 

 lettuce and a crop of beets or cucumbers can be taken from the 

 same area in a single season. This plan provides for a succession of 

 crops and keeps the frames in constant use from December to May. 



FIG. 107. Lettuce in muslin-covered frames 



South of the limit for the economical use of glazed sash, lettuce 

 is extensively grown in muslin-covered frames about 1 5 feet wide 

 and from 100 to 1 50 feet in length, like those shown in figure 107. 

 The treatment of plants in muslin-covered frames is the same as 

 for those in sash-covered frames. The plants are grown in properly 

 protected seed beds and, when large enough, are transplanted to 

 the frames. In the neighborhood of Wilmington, North Carolina, 

 the plants are set the last of October and harvested for the holi- 

 day market. A second crop is sown in December and put in the 

 frames in January or February, to be harvested in April. This 

 crop is usually followed by beans or cucumbers. 



