locations with similar winter climate, it appears doubtful that commercial tree fruit production 

 will ever become important in the central Great Plains.' 



Performance of some of the hardier varieties of sour cherries which survived the adverse 

 climatic conditions at Cheyenne has led investigators to conclude that some varieties can be 

 grown satisfactorily for use in farm and home gardens in the Central Great Plains area. 



The search for hardy and disease tolerant rootstocks and interstocks is also going forward 

 along with the breeding and selection of varieties for fruiting, either grown on their own 

 roots or budded on compatible rootstocks. Use of Montmorency sour cherry as an interstock 

 is being studied at Prosser and a number of other cherries are being evaluated as potential 

 hardy rootstocks for sweet cherry in the Northwest. Among the possibilities being investigated 

 are Primus fortanesiana, P. jruticosa, P. dropmoreana, P. mahalab, and virus-free Stockton 

 Morello sour cherry. 



Peaches 



Development of cold-hardy peaches adapted to the needs of various sections of the United 

 States has long been a major objective of peach improvement programs. However, the task 

 is complicated by the wide variation in climatic conditions in this country and the need for 

 combining cold hardiness with other desirable characteristics such as high quality and nema- 

 tode resistance. 



USDA scientists have worked to develop varieties to meet the varying needs of the 

 different areas — varieties resistant to cold winter temperatures for the Northern States; varie- 

 ties resistant to spring frosts for the Central States; varieties resistant to rapid changes in 

 temperature and having low chilling requirements for the Southern States; and varieties 

 resistant to extreme winter cold and to drought for the Great Plains. 



At the State experiment stations, breeding projects have usually been geared to local 

 needs: In Iowa, to hardiness of tree and flower buds to low temperatures; in Missouri, to 

 superior fruit qualities with winter hardiness and late blooming; in New York, to commercial 

 varieties relatively resistant to low winter temperatures with special emphasis on winter 

 hardiness of flower buds; in South Dakota, to sufficient drought resistance and winter hardi- 

 ness for growing in farm and home orchards of the Great Plains. 



A major difficulty in the search for peach varieties adapted to growing in areas with 

 severe winters is the tendency of most kinds to begin to bud after a short period of exposure 

 to warm temperatures. 



In greenhouse experiments, only 15 to 20 days at constant temperatures of 70° F. were 

 required to induce blooming in most peach varieties after their rest period had been com- 

 pleted. Apples, on the other hand, required about 25 days of 70° F. temperature following 

 rest. 



Budding trees are much more tender than dormant ones. Although peaches will with- 

 stand temperatures as low as —20° F. when fully hardened, temperature of —10° F. will kiU 

 buds of many peach varieties. For this reason prospects for developing varieties adapted to 

 growing commercially in the Great Plains do not appear encouraging for the foreseeable future 

 at least. 



Even the addition of 1 degree in ultimate cold hardiness of buds could mean a partial 

 crop rather than none when temperatures are in the critical range for cold damage. Hence 

 the search for hardier varieties is going forward, with the prospect that even small gains in 



AHhough some sour cherries are produced commercially in the locah'ty between Loveland and Well- 

 ington, Colo., on the sheltered plains immediately East of the Rocky Mountains, production in 1960 was 

 only a fourth of what it formerly was. 



