48 



No root injury, whatever, occurred to the trees stored in a cool, 

 dry cave and it was inferred that cold and dryness are the im- 

 portant factors in causing root injuries. 



The fact that root injuries are so severe in dry soil is that the 

 cold, dry air comes in contact with the roots and dry freezing re- 

 sults. 



Trees whose roots are entirely killed or severely injured are 

 likely to die immediately, and before growth begins. Trees less se- 

 verely injured may start into growth and then suddenly die with a 

 crop of fruit upon the trees, while still others may continue a lin- 

 gering existence until insects and diseases and further winter in- 

 juries overcome a waning vigor. 



How can we prevent or lessen the dangers of root injuries? We 

 know that certain stocks are more hardy than others and in districts 

 where much root killing occurs this is a matter of the first im- 

 portance. In general, root injuries to fruit trees in central At- 

 lantic Coast districts are not of the most severe kind, and, yet, 

 minor injuries in certain forms may finally result in much damage. 



A good cover crop upon the soil will tend to prevent deep 

 freezing ; it will also help to retain snow and moisture, and may be 

 an important factor in the prevention of root injuries in winter. 



Twig and wood injuries commonly occur in connection with 

 root injuries, but such is not always the case. The twigs and 

 branches of trees are sometimes injured when no root injury occurs 

 and vice versa. 



Very low temperatures are likely to result in considerable kill- 

 ing back or twig injury, especially upon the more tender fruits. 

 This is most severe upon strong, rich, moist soils where a late 

 wood growth occurs or where a severe drought suddenly stops wood 

 growth in mid-summer. Varieties of apples, peaches and other 

 fruits which ripen their crop relatively late in the season are often 

 more severely injured than varieties which ripen their fruit early. 

 The late maturing varieties are obliged to keep in a more active 

 growing condition in order to mature their crop, and have a very 

 short time in which to give their entire energy to the maturing of 

 fruit buds to withstand winter conditions. An example of this oc- 

 curred in New Jersey in the winter of 1910-1911, when the fruit 

 buds of many late varieties of peaches failed to pass a comparatively 

 mild winter successfully. We undoubtedly have two extremes to 

 guard against, a too prolonged wood growth and a too sudden and 

 early check to wood growth. The former may be of much greater 

 importance in northern fruit districts, but the latter is of equal or 

 more importance in southern New Jersey and districts south of that 

 locality. 



In severe winters, injury to the sap wood of the larger branches, 

 and the trunk may occur in addition to twig killing. The young sap 

 wood may be killed while the cambrium remains alive and continues 

 growth the following spring. The injured wood becomes spongy, 

 commonly turns brown or black, and a split trunk or a broken 



