144 THE PRINCIPLES OF PRUNING 



heavy pruning on the tree, and the injury result- 

 ing from the wounds. In the dry and cold cli- 

 mates of the North, Northwest and the Plains, 

 there is excessive evaporation from winter-made 

 wounds, and this injury may be so great as to 

 make severe winter pruning inadvisable in many 

 localities. (See Section 17.) It is therefore dif- 

 ficult to judge of the merits of controversies con- 

 cerning the advisability of the heavy pruning of 

 winter -injured trees, particularly in severe cli- 

 mates, because two or more unanalyzed problems 

 may be involved. 



Since opinions differ as to the advisability of 

 severely heading -back trees which are much in- 

 jured by cold, I here insert extracts from letters 

 of various fruit-growers in the Northwest, to 

 whom I was referred by E. S. Goff, of the Uni- 

 versity of Wisconsin. Professor Goff himself 

 writes as follows: 



" I have discussed the question as to the advisability of 

 pruning winter- injured trees with Wisconsin friends. Some 

 of them are very positive that pruning such trees in spring 

 has caused their death in several cases ; also that similar 

 trees not pruned until they had recovered vigor, have out- 

 grown the effects of the winter and made good trees. The 

 hypothesis that I have used to explain the opinions that 

 such trees should not be pruned in spring is this: The 

 buds, being enfeebled by cold, are not able to use a large 

 quantity of water from the roots, and hence thinning out 

 the buds, which naturally tends to increase the pressure of 

 sap in the remaining ones, proves injurious. That this is 

 true, I am by no means sure, but the fact that winter- 



