324 FUNDAMENTALS OF FRUIT PRODUCTION 



shown to be of relatively small importance in the peach, though it is by- 

 no means unknown. Extensive killing occurred in the Michigan peach sec- 

 tion in a freeze on Oct. 10, 1906, while the trees were still in full foliage. ^^^ 

 At South Haven the temperature fell to 17°F., and some unofficial ther- 

 mometers registered 6°F. Cambium and sap-wood injuries extending to 

 the snow line were common. Frost cankers on peach trunks and crotches 

 are found sometimes, following winters of extreme cold or a late growing 

 season. ^^ "Gum pockets usually form under the flattened areas and the 

 gum often oozes out during periods of wet weather. The injured area is 

 usually rather indefinite about the margin and the formation of a healthy 

 roll of callus is thereby much retarded." 



It has been shown earlier that no stated temperature can be assumed 

 as fatal. However, fruit buds are generally more tender than wood. 

 When, therefore, there occur cases in which the wood is killed and the 

 buds survive, they may be considered good evidence of lack of maturity. 

 There is hardly a winter without some killing back of young twigs which 

 may be interpreted as indicating a lack of maturity. The care generally 

 exercised in selecting sites for peach orchards to secure freedom from 

 spring frosts fortunately has another equally desirable, though seldom 

 recognized, effect in that it secures greater maturity. There is a remark- 

 able uniformity, throughout reports of various freezes in northern 

 states, in locating the greatest injury in trees growing in moist, rich soil 

 and receiving late cultivation. Another point of agreement is the ascrib- 

 ing of great injury to trees low in vitality from various causes such as 

 San Jose scale, leaf curl, low fertility, borers and poor drainage. Green 

 and Ballou^i mention an orchard in which the San Jose scale spray was 

 omitted in 1902 on three rows running through the middle. In the 

 severe winter of 1903-1904 these three rows were killed while the rest 

 were uninjured. Whether the greater injury to weak trees is actual and 

 due to some specific condition characteristic of weakness or whether it is 

 apparent and due to their inferior recuperative powers is not clear. A 

 given degree of injury would be more evident, certainly, on a weak than 

 on a strong tree. 



Waite,^^^ reporting on the January, 1904, freeze in New York, dis- 

 tinguished three classes of injury: " (1) In bearing peaches the trees most 

 injured by freezing show the bark entirely blackened and dead, more or 

 less separated from the trunk and the wood turned a very dark brown 

 color. The injury extends far up onto the limbs although the bark 

 usually has not separated on the branches. Such trees are dead beyond 

 all question. The bark on such trees still retained its vitality. Some- 

 times a rise of 10 or 15 feet resulted in trees being less seriously 

 injured. (2) With many peach trees the bark is lightly separated from 

 the wood which is of a dark-walnut color next to the cambium and brown 

 throughout. Though still alive the bark is somewhat browned and 



