8 WEET-POTA TO 447 



should be turned into alternate middles, using a stick, 

 so as to get them out of the way of the implement. At 

 the next cultivation, the position of the vines is reversed. 

 Tillage usually ceases when the vines meet across the row, 

 though it is still desirable to pull or remove with a hoe 

 large weeds and bunches of grass. 



Some cultivators are equipped with a vine-lifting attach- 

 ment, which makes it unnecessary to move the vines into 

 alternate middles by hand. 



423. Pruning the vines. Experiments have shown 

 that pruning the vines in order to obtain vine cuttings 

 for propagation reduces the yield. The few experiments 

 so far made do not agree in showing any advantage from 

 the custom of lifting or moving the vines late in the season 

 to prevent their rooting at the joints or nodes. 



HARVESTING AND STORING SWEET-POTATOES 



424. When to dig potatoes. The root of the sweet- 

 potato has not reached maturity and condition for storage 

 until, when a cut is made, the wound heals over with a 

 whitish appearance. If the broken place becomes dis- 

 colored, the potato is immature. 



Since the price is much higher in August and early in 

 September than during October and November, a part of 

 the crop may be dug very early, even at a sacrifice of yield 

 and maturity. The bulk of the crop is not dug until about 

 the time of the first fall frost. Some prefer to dig potatoes 

 before they are touched by frost, but the frosting of the 

 vines does no harm if harvesting is then done before the 

 decay extends from the vines to the roots. Late digging, 



