Propagation 83 



seed. Most sweet potato authorities now advocate grow- 

 ing seed from vine-cuttings. The potatoes grown from 

 vines are not only practically free from disease but they 

 seem to keep better in storage and are about the proper 

 size for seed. Frequently the main crop is grown from 

 vine-cuttings, only enough sets being planted to pro- 

 duce vines suiBcient to set the required acreage. This 

 practice is not only satisfactory in-so-far as disease con- 

 trol is concerned, but is more economical than purchas- 

 ing or raising enough plants for the entire acreage. 

 When a machine is employed for setting such plants, 

 all or most of the leaves must be stripped from the cut- 

 tings to facilitate handling. The cuttings are made as 

 soon as the vines are 3 or 4 feet long. Pieces Y or 8 

 inches long containing about two joints are commonly 

 used. These cuttings are usually made from the early 

 vines grown from slips. Setting and handling is done 

 the same as with slips. It is generally conceded by 

 growers that after the vines have begun to run well, the 

 use of vine-cuttings is much to be preferred to the slips, 

 especially for the late crop. However, except for the 

 advantages already mentioned, experiments have shown 

 practically no difference in yield. It has been found 

 that too close pruning of the vines will decrease the 

 yield of marketable potatoes by increasing the percent- 

 age of smaller ones.^ 



The effect of constant propagation by vine-cuttings 

 and the influence on yield of constant selection of cut- 

 tings from plants with the most vigorously growing 

 vines are problems yet undetermined. , Individual 

 plants of the same variety growing side by side often 

 1 G. W. Carver, Bull. 30, p. 7, Tuskegee Normal and Ind. Inst. 



