94 POMOLOGY 



synthesis of the tree and hence profoundly disturb its re- 

 lation with the amount of soil-moisture and nutrients 

 taken up by the undisturbed root system. To what extent 

 a reduction in the top of the tree will affect the amount 

 of water and mineral nutrients absorbed by the roots can- 

 not be stated definitely at this time, but certainly each 

 growing point remaining must receive a greater supply 

 than had no pruning been practiced. This, then, would 

 seem to account in part for the apparent stimulation to 

 growth which takes place. 



Critical observation has shown that heavy pruning will 

 result in dwarfing of a tree, as already noted. This is ex- 

 plained on the grounds that fewer growing points must 

 necessarily produce less total linear growth and hence less 

 weight and, therefore, the top of the tree is somewhat re- 

 duced. This dwarfing in the top will react on the root 

 system and it will become restricted. 



81. When to prune. — ^Divergent views have been held 

 as to the best time to prune fruit-trees, but careful obser- 

 vations are bringing about more unity of opinion. An old 

 adage says ''Prune when the knife is sharp," but another 

 admonishes not to prune frozen trees and not to prune 

 when the sap is "running"; so the layman has been left 

 somewhat confused. Little actual experimental work has 

 been done along these lines but much experience may dic- 

 tate practice. From an experiment with apple trees con- 

 ducted in Minnesota, where the winter temperatures are 

 low, it is concluded that no difference in the healing of the 

 wounds resulted whether the cutting was in fall, midwinter 

 when the trees were frozen, or in the spring.^ With hardy 

 fruits it is not uncommon to prune at any time during the 

 dormant season, but preferably in late winter or early spring. 

 With the grape, peach, and other fruits hable to winter in- 

 1 Brierley, W. G. Proc. Amer. Soc. Hort. Sci. 1919. p. 102. 



