132 Principles of Plant Culture. 



the freezing point. But in localities subject to frost, the 

 liability of damage to vegetation from this cause is gov- 

 erned more by cold air drainage (210) and proximity to 

 water than by latitude. It is as important to select loca- 

 tions for peach growing with reference to spring frosts in 

 the Carolinas as in the peach belt of ilichigan, and 

 favorable locations for the apple in ^^"isconsin sometimes 

 escape damage from spring frosts in seasons when the 

 apple crop is cut off by frost from extensive regions of 

 the southern states. 



217. Methods of Preventing Injury l)y Frost. Any non- 

 conducting material lying between the earth and space, 

 whether spread directly upon the earth or at a consider- 

 able height alio\-e it, acts as a blanket to intercept the 

 radiating heat, and thus prevents in a. measure the cool- 

 ing of objects beneath it. For this reason, straw, muslin, 

 or other non-conducting material spread over iilants, 

 usually protects them from frost. 



AVhile it is easy to protect a few plants from frost by 

 covering them directly, it is much more difBcult to pro- 

 tect large plantations in this manner. Considerable 

 plantings of the sti-awberry have been successfully pro- 

 tected from fjost by covering the rows in the e\'ening 

 with straw or marsh hay, and «-here these materials are 

 convenient, tlie work may often be cheaply and quickly 

 performed. 



Attempts to prevent frost on a large scale by the heat 

 of fires or Ijy burning material that produces much 

 smoke or vapor, have not been sufaciently successM to 

 comnrend these methods for general application. 



