66 Diagnosing of Diseases 



Late pruning in summer will produce such late growth and 

 is, therefore, to be avoided. 



The late or spring frosts will injure mainly the new tender 

 growth of leaves and flowers, and the opening buds. A 

 temperature from two to even seven degrees above freezing 

 point may suffice to do the damage. Southern, eastern, 

 and southeastern exposures are especially dangerous, for in 

 these sun-warmed situations vegetation awakens in early 

 spring and the tender foliage falls readily a victim to the 

 late frost. 



Shade, or any other method of keeping the soil cool and 

 retarding the activity of roots and buds is the only means of 

 counteracting these frosts. In most cases they have to be 

 endured, or avoided by selecting late budding species and 

 varieties. 



Winter cold, as a rule, does not do much damage, yet 

 occasionally very severe and persistent cold, causing frost 

 to penetrate the soil to a great depth, may become detri- 

 mental, injuring or even kilhng trees and shrubs. This 

 is especially true when the preceding season has been unfav- 

 orable, or for other reasons the plants have had their vitaHty 

 impaired. Soil conditions and situation have considerable 

 influence on the occurrence of winter killing, just as they 

 have on early and late frosts; high, dry ground and exposed 

 places being especially subject to this damage. Even 

 native species are by no means exempt. The loss may be 

 only in buds, or in twigs, but, if the roots are killed, the 

 entire plant may succumb. During the severe winter of 

 1903-1904, Red Maple, Butternut, and White Pine in the 

 State of New York were killed outright, and a long list of 

 trees and shrubs were partially killed. The loss of part 

 of the root system may exhibit itself, as in any other case 

 of reduced water-supply, in the loss of part of the crown 



