254 Subtropical Vegetable-Gardening 



Potato Diseases, Maine Exp. Sta. Bulletin 149, 1907. 



The Improvement of the Potato, 111. Exp. Sta. Bulletin 127, 1908. 



Potato Growing, Minn. Exp. Sta. Bulletin 114, 1909. 



The Potato as a Truck Crop, U. S. D. A., Farmers' Bulletin 407, 1910. 



SWEET POTATO 



The sweet potato is a tropical plant which is cultivated 

 in most tropical and subtropical countries, and especially 

 in the southern United States. In warm countries, it 

 commonly produces some fertile seed, and new varieties 

 can be obtained from these, as is done with the Irish 

 potato. There has not been much systematic work done 

 in this direction, though a beginning has been made in 

 some tropical countries. The plant is remarkable for 

 the ease with which cuttings of the green vines take root, 

 and this is the commonest method of propagation. Its 

 tuberous roots contain about the same percentage of 

 starch as the Irish potato, together with a variable amount 

 of sugar. 



This crop is cultivated extensively in the southern 

 states. It may be grown successfully as far north as 

 Nebraska and New York, but in these sections it cannot 

 be regarded as more than a garden product. 



Soil for the sweet potato. 



Nearly all land in the South is adapted to this crop, 

 but clay soil is not as good as loam. The opinion that rich 

 land is not suitable is a mistake. Some of the very best 

 crops have been raised on drained muckland. The sweet 

 potato is so tolerant that it is difficult to find land that will 

 not produce a fair crop. To produce a large crop, warm 



