Importance and Distribution 17 



newal or second growtli of the tubers which causes ex- 

 cess sappiuess and makes handling in transit .more 

 difficult. On the other hand, severe drouths late in the 

 season make harvesting tedious. 



Where irrigation must be practiced, as will be nec- 

 essary in some parts of Texas, New Mexico and Ari- 

 zona, most of the water should be applied between the 

 time the plants are set and the ground becomes covered 

 with vines. The water is withheld altogether for several 

 weeks preceding harvest, to permit the proper ripening 

 of the tubers. 



A climate with an abundance of sunshine and warm 

 nights is necessary for thrift. A temperature ranging 

 from 70 to 100 degrees F. during the summer growing 

 period is a good average for maximum yield, although 

 in a small way " sweets " may be produced under a 

 wide range of temperatures as well as soil types. North 

 of the cotton-belt, the sweet potato is commonly re- 

 garded as a garden crop. 



The sweet potato crop is exceedingly sensitive to frost 

 and growth is noticeably checked by cool weather. 

 Growers in the southern Gulf states have found it 

 profitable to set their plants in tbe field a little later 

 in the spring rather than have them stunted by the 

 ■ cool nights. The sweet potato is strictly a summer crop 

 and grows best in the hottest part of the year. 



It requires about four and one-half months for the 

 sweet potato to reach normal maturity. A potato that 

 is immature is harder to keep in storage and shrinks 

 more than one fully mature. The amount of starch, 

 sugar and other constituents as well as their form and 

 availability differ materially at various periods of 

 growth. The relative length of the growing period is 



