120 HATCH EXPERIMENT STATION. [Jan. 



when they were tender, and frequently results in almost com- 

 plete defoliation of apple trees during August. This trouble 

 has been studied by Sorauer in Germany, by Stewart in New 

 York, and l)y Stone and Smith in this State. 



Some of the conditions which underlie winter-killing are 

 as follows : — 



Severe cold, causing frost to penetrate to a great depth. 



Sudden and severe cold following a prolonged warm spell 

 in the fall, in which case the wood tissue is tender and im- 

 mature. 



Conditions which favor a soft growth and immaturity of 

 wood. Various causes may be responsible for thiS; such as 

 growth in a low, moist soil, too heavy manuring or fertil- 

 ization, or absence of sufficient sunlight. 



General low vitality, caused by insect pests and fungous 

 diseases and lack of moisture in the soil. 



Insufficient soil covering, such as lack of organic matter, 

 light mulching and snow covering in v/inter. 



Location in unusually windy and exposed places, etc. 



Species with a limited maximum range for cold are es- 

 pecially susceptible. There are innumerable examples at 

 hand which will furnish illustrations of the various causes of 

 winter-killing. For example, low vitality is well illustrated 

 by the large number of old apple trees which have died in 

 the last two years. The old, neglected orchards were the 

 worst sufferers from the effects of winter-killing, and many 

 isolated trees, such as cherry trees that had received no care 

 for some years, were badly affected. 



In one instance a number of peach trees and various kinds 

 of slii'ubbery, both native and exotic, were severely injured 

 where located near an overflow from a cesspool, while similar 

 shrubbery near by was not injured in the least. This injur^^ 

 was due to the more rapid and tender growth of those plants 

 which received benefit from the cesspool overflow. Per- 

 fectly hardy native plants, being deprived of a normal 

 amount of light or grown in too dry places, are winter-killed 

 readily ; and Japanese maples on high, dry ground with 

 severe exposure are extremely subject to winter-killing. 



B\' far the most noticeable effects of winter-killinof have 



