PRINCIPLES OF PLANTING AND CULTIVATION 45 



The provisions necessary for the growing of sweet potatoes at 

 the North are the most elaborate required for any extensively grown 

 truck crop except tomatoes. Figure 10 illustrates very well the gen- 

 eral appearance of a sweet-potato bed constructed according to the 

 plan outlined above. 



Celery. While celery is extensively grown in certain parts of 

 California, Ohio, Michigan, New York, and Florida, the plants 

 are usually started in beds in the open. For some of the extremely 

 early crops at the North it is necessary to start plants in green- 

 houses or hotbeds, but for the main crop it is sufficient to sow seed 

 in the open, in rows or broadcasted in specially prepared beds. 

 In some cases the plants must be transplanted before being finally 

 set in the field. Ordinarily, however, when celery is grown on 

 an extensive scale, the plant bed is simply sheared or gone over 

 with a light mowing machine in order to reduce the top surface, 

 and then with a special digging machine the plants are lifted and 

 immediately set in the field, usually by hand. 



Tobacco. As a rule tobacco is grown in much the same way as 

 celery. The common practice in some of the extensive tobacco- 

 growing regions is to place brush or other combustible material 

 over the area which is to be used as a seed bed, and to fire this 

 early in the season so as to destroy the weed seeds and warm up 

 the soil. This provides suitable conditions for the germination 

 and growth of the tiny seeds of this plant. In some cases it is 

 only necessary to provide a sheltered place for the seed bed. 

 Sometimes sash are used, but generally the seed bed is made in 

 the open in a place convenient for watering and weeding, and the 

 plants grown without special attention to transplanting until they 

 are large enough to be lifted and placed in their permanent loca- 

 tion in the field. In regions where tobacco is the staple crop, 

 particularly at the North, transplanting is carried on by machinery, 

 which greatly facilitates the work and materially reduces the cost. 

 There are several types of transplanting machines, among which 

 the one shown in figure 1 1 is a fair representative. 



Machinery for transplanting. Sweet potatoes, tomatoes, and 

 tobacco are the three crops which are most extensively planted by 

 machinery at the present time. The feasibility of handling cabbage 

 in this way is receiving attention by the extensive growers because 



