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 killing trees and shrubs. This 
is especially true when the preceding season has been unfav- 
orable, or for other reasons the plants have had their vitality 
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 
