250 CALIFORNIA VEGETABLES 



safety from fall frosts. It takes about 12,400 plants per acre. Each 

 seed potato will produce a first crop of about eight plants and three- 

 fourths as many at later pullings. If only the first pulling is to be 

 used, it is safe to allow 90 or 100 square feet of hot-bed per acre 

 to be planted. This will require about 300 pounds of seed potatoes 

 per acre. Fewer seeds are required if the second and third crops 

 of plants are used, but such plants will produce crops that much 

 later. 



Planting. Most sweet potatoes are grown on ridges about 

 fourteen inches high and three feet apart to secure greater heat 

 in the soil and to facilitate irrigation, but flat culture is also prac- 

 ticed and in some regions is preferred. After the land is well 

 prepared and harrowed down smooth, mark off the rows three feet 

 apart and set the plants eighteen inches apart in the row. When the 

 ground is thoroughly warmed by the advance of the season, say in 

 April or May, take the shoots as described above trimming the 

 roots to a length of four inches, though some, planting by hand, 

 use long roots. They must, of course, be kept from drying out, the 

 young roots being very tender. In taking them to the field they 

 must, therefore, be kept in a bucket of water, or in a wet sack, the 

 former being the best. Plant out the shoots eighteen inches apart 

 in the rows, one in a place, settling them down in the soil, deep 

 enough to find permanent moisture. 



Sometimes when the object is to get unusually large potatoes, 

 instead of pulling off and setting out the slips, the potato is lifted 

 out and with every slip a small piece of the potato is cut out and 

 planted with the slip. This method will bring the earliest potatoes, 

 but the number of sets are many less than though the potato be 

 allowed to remain in bed for their continued production. 



Recently a machine has come into use which digs a trench on 

 the top of the ridge and drops water at whatever intervals are de- 

 sired. Three men, including the driver, transplant two acres per 

 day by machine. The machine opens trenches on two ridges at 

 once, and closes them soon afterward. In the interim the two men 

 sitting on the machine close to the ground, insert plants in the 

 opened trenches about fourteen inches apart, holding them until the 

 machine draws dirt around them. A water tank on the machine 

 automatically wets the plants when set, and is refilled from the irri- 

 gation ditch at the end of each row. 



Cultivation. Cultivation for the purpose of weed killing and 

 surface stirring is continued until the vines interfere and after that 

 the vines cover the ground with a thick mat and discourage weed 

 growth. 



Irrigation. The plants are irrigated three or four times per 

 season and cultivated after each except the last, when the vines are 

 in the way. After the vines begin to run, need of irrigation is told 

 by their tips, which show lack of water before any other part of 

 the plant, by drooping. Water is then necessary at once. 



