WINTERKILLING 15 



through the drying out of the young shoots, due to the 

 fact that, while some evaporation still goes on during 

 the winter, the tree cannot take up water from the 

 frozen soil to make good this evaporation. The young 

 shoots, therefore, become so thoroughly dried out dur- 

 ing cold weather that the tissues are killed. Some va- 

 rieties, of course, are more subject to this damage than 

 others, and in northern regions a distinct variation of 

 hardiness among different varieties is well recognized. 

 The Russian apples, so widely recommended a few 

 years ago on account of their superior hardiness, are, 

 as a class, conspicuous for their ability to withstand 

 this sort of damage. 



There are no very certain means of preventing win- 

 terkilling of this kind. Anything which can be done 

 to prevent the ground from freezing deeply and for 

 a long period will give the best possible protection. 

 Heavy cover crops which hold the snow and protect 

 the soil from freezing are especially valuable. It has 

 usually been said that pains should be taken to have 

 the wood ripen up as early in the fall as possible as a 

 means of guarding against winterkilling. This theory 

 has unquestionably been overworked. 



Root killing is doubtless the most serious form of 

 winter damage suffered by apple trees in northwestern 

 localities. The great freeze of February, 1899, which 

 killed hundreds of thousands of trees in the north- 

 western states, accomplished this destruction chiefly 

 by root killing. The ground was bare of snow at the 

 time and the cold was very intense. When it is con- 

 sidered that all ordinary orchard trees are grafted or 

 budded upon miscellaneous stocks, it is easy to under- 

 stand that nearly all of these stocks might be more 

 tender than the l^ardy varieties which had been grafted 



