266 IRISH POTATOES 



easily grown in Scotland. The warmer climate of England is less 

 favorable. 



In Europe great potato crops are grown in the cool summers of 

 North Germany, the Netherlands, and Scandinavia, while the pro- 

 duction is much less in South Europe or the hot summer climates of 

 the interior of Hungaria or Russia. 



In the United States the most favorable summer climate is found 

 in the northern tier of States, especially Maine, which is noted for its 

 large acre yield. High elevation has the same effect as northern 

 climate, and we find ideal summer climate in Colorado, and north 

 through the Rocky Mountains, and in the northwestern Pacific 

 States. Farther south or in regions with hot, dry summers, it is 

 necessary to handle the crop so as to avoid the summer heat. This 

 is accomplished in the South by planting in midwinter, so the crop is 

 made before dry summer heat. Sometimes they are also planted in 

 midsummer, but make their principal growth in the cooler weather 

 of fall. 



Degeneration. It has long been known that potatoes continu- 

 ously grown in regions of hot summers will rapidly degenerate and 

 become unproductive. In the South they find it necessary to buy 

 seed potatoes from the North every year. Maine has long been a 

 great seed-growing center, because of the favorable climate. Also 

 New York State, Michigan, Wisconsin, and the Red River Valley 

 produce good quality of seed. Good seed is also produced at high 

 elevations farther south. 



At the Nebraska Experiment Station 2 a very interesting experi- 

 ment was tried. By mulching the potato ground with six inches of 

 straw it was possible to not only keep the soil moist, but several de- 

 grees cooler than under ordinary culture. Above the straw, however, 

 the tops were exposed to even greater heat than ordinary. It was 

 found that the potatoes grown under straw retained their productive- 

 ness for years, while the same potatoes under ordinary culture 

 rapidly degenerated. Even degenerate potatoes could be restored 

 to strong vitality and productiveness by growing under straw for 

 one year. This experiment is believed to demonstrate the im- 

 portance of a cool, moist soil for growing seed potatoes. 



1 Annual Report, 1912. 



