272 CULTURE OF IRISH POTATOES 



Then followed three dry years, in which yield was reduced to one- 

 half, and the potatoes lost vitality and ability to yield. This was 

 demonstrated by importing new seed from Nappan, Nova Scotia, in 

 1909, and growing beside home-grown seed. Results in 1909 were 

 as follows: 



Rose Carmen Vick's extra early 



Nappan seed 215 198 171 



Home-grown seed 44 83 74 



In 1910 seed of eleven varieties from Indian Head was brought 

 in for comparison : 



Source Average yield per acre, bushels 



Indian Head seed 368 



Home-grown seed 96 



Other data could be cited, but the above is sufficient to show the 

 injurious effect of dry, hot weather on vitality of seed. 



In general, in the northern tier of States, potatoes retain vitality 

 very well, but further south good seed can only be produced as a 

 regular practice at the higher elevations, in the mountainous 

 districts. 



Second Crop Seed. In the South the difficulty is sometimes 

 overcome by growing what is known as " second crop " potatoes. 

 These are planted about August, and develop tubers during the cooler 

 fall weather. They are killed by frost and' harvested green. These 

 potatoes have good vitality, the only objection being that they are 

 rather slow and irregular in germinating when planted the following 

 spring. 



Immature Seed. In Europe it has long been held by many that 

 seed potatoes, harvested green, had greater vigor and productive- 

 ness than mature seed. For this reason many growers plant their 

 seed stock late, so the vines are killed by frost before the crop is 

 mature, and use this for seed rather than seed that has normally 

 matured. 



Storage of Seed. Seed stock should be stored in a cool place, 

 and kept solid and perfectly dormant until planting time. This 

 requires a temperature of 30 to 40 F. All potatoes are very 

 dormant when first mature, but they slowly ripen in storage, and, 



