332 FUNDAMENTALS OF FRUIT PRODUCTION 



experimental data are very meager. Field observations as recorded are 

 frequently contradictory and puzzling. A certain variety, for example, 

 half hardy in New York would be expected to be wholly adapted to 

 Georgia; actually it may prove fully as tender in the south as in the north. 

 The red raspberry as a group is generally conceded in northern regions to 

 be hardier than the blackcap group yet the reverse condition obtains over 

 wide areas. ^^ Though loganberry and other western dewberries are very 

 tender, in one winter at Corvallis, Ore., with a minimum of 20°F., when 

 Cuthbert raspberries were killed at the collar the loganberry was un- 

 harmed. Furthermore, cane fruits frequently suffer from drought injury 

 which is doubtless sometimes confused with winter injury and so reported. 



Winter injury to cane fruits may take one of several forms. Root kill- 

 ing occasionally occurs, especially in dry, cold climates with little snow. 

 Where this occurs, covering the canes is of no avail unless the roots 

 also are covered. In other cases the canes may kill to the ground, or 

 they may kill part way back, or the laterals may kill. Immature canes 

 appear to kill more easily at the tips and close to the ground and would 

 sometimes be benefited by mounding. The canes may be weakened only 

 and blossom but fail to mature the crop. Under exceptional conditions 

 currant and gooseberry fruit buds may be killed while the stems live. 



Immaturity Most Important.— It is a generally accepted principle in 

 the growing of cane fruits that maturity is important to hardiness. Imma- 

 ture tips, laterals on canes pinched back and suckers that develop late are 

 sometimes injured by comparatively mild freezing; a temperature of 12°F. 

 in November has caused extensive damage to raspberry tissues of this 

 sort in Missouri. Even in Virginia caution about late cultivation, 

 inducing an immature and tender growth, appears necessary.^ That the 

 degree of maturity attained at the onset of cold weather can be modified 

 by cultivation, irrigation and fertilization is obvious. 



Relation of Summer Pinching to Maturity. — The effect of pinching 

 on raspberries in northern sections where maturity is clearly a factor 

 with tree fruits is well illustrated by Table 51, which shows the resistance 

 to winter killing of different varieties pinched at 15 to 20 inches and of the 

 same varieties unpruned. It is evident that the lateral growth induced 

 by pinching is not so hardy as the unbranched canes; presumably this is 

 due to immaturity. 



A statement of Michigan experience is not without interest. ^^^ 

 "Hansell, King, Miller [red raspberries] seldom branch and should not 

 be pinched back. When allowed to grow naturally the canes form strong 

 buds from which the fruiting branches will be developed the following 

 season while if the ends are pinched the buds will develop the first year 

 into slender shoots upon which the fruit buds will be weak, . . . [with 

 an] increased tendency toward winter-killing. Hence, for non-branching 

 varieties pinching back is not to be recommended." However, Card*^ 



