THE SEARCH FOR HARDIER FRUITS AND NUTS 



Every year many individual farmers suffer small to heavy crop losses due to cold damage. 

 Even in years when ordinary cold conditions prevail, these losses add up to millions for the 

 country as a whole. And in the infrequent years of major freezes losses are sometime deva- 

 stating for individuals and areas involved. At such times, consumers are also losers, due 

 to shortages and resultant high prices, and low quality produce. 



In the case of fruit trees and nuts, whole orchards have been heavily damaged or lost 

 in some severe freezes. When this occurs, the crop potential is seriously curtailed for a 

 period of years until the damaged trees can be replaced and brought back into production. 



Use of cold hardy plants has long been the farmer's major defense against extreme or 

 unseasonably cold weather when protective cultural practices such as mulching and the use 

 of shelterbelts or emergency measures including the use of wind machines or portable heaters 

 would be ineffective or uneconomic. 



But hardy varieties with other desirable traits are not always available for the particular 

 area or crop to be planted. However, crops research scientists have been working for many 

 years to discover plant varieties which are more tolerant to extreme cold or sudden and un- 

 timely drops in temperature than those currently being cultivated in this country. And, as a 

 result of these investigations, farmers in many instances are now better able to defend them- 

 selves against the vagaries of the weather than were farmers in the past. 



A COMPLEX PROBLEM 



Many factors affect the ability of fruit and nut crops to withstand cold damage under 

 particular conditions. 



The different kinds and varieties of plants vary in the minimum cold they will tolerate 

 when they are fully hardened and other conditions are optimum. The lowest temperature 

 that a plant can tolerate under the most favorable circumstances is referred to as its ultimate 

 (or absolute) cold resistance. 



Because of the many variables affecting hardiness, a plant's ultimate cold resistance is 

 only one measure of its ability to survive adverse winter conditions. For example, a fruit 

 tree that is hardy in terms of ultimate cold hardiness may have early-blooming flowers that 

 are very susceptible to frost. Or a berry bush that can survive extreme cold may not be truly 

 hardy in many sections of the Northern Great Plains because it is unable to tolerate winter 

 drought conditions prevailing there. 



Within the different plant varieties, cold hardiness varies with the general condition of the 

 individual plant, its maturity, the extent to which it is exposed to minimum outside tempera- 

 tures or is protected by vegetative ground cover, snow, or windbreaks. Plants can withstand 

 much lower temperatures during dormancy or periods of rest than when they are growing. The 

 amount of cold a plant can stand under a particular set of climatic conditions is also affected 

 by when and how rapidly the variety develops cold resistance with the coming of cold weather 

 and how long it maintains this resistance or the speed with which it regains it following the 

 advent of unseasonably warm weather during winter. 



