FROST ENDURANCE 119 



The general reader, after studying the foregoing data, may 

 conclude that in nearly all the valley districts of California there is 

 little difference in the length of the absolute frost-free period; also 

 that elevation influences temperature similarly in all parts of the 

 State. At elevations below 1500 feet, which is the point at which 

 foothills begin to shade into mountains, there are about two-thirds 

 of the whole year in which even the tenderest vegetation may be 

 considered practically safe from injury from frost, and particular 

 situations in which the frost-free period is even longer. On the 

 other hand, there are mountain valleys, with good soil and sunshine 

 and ample total heat for vegetables, in which tender plants must 

 be always protected, because frost may occur every month in the 

 year. 



The Endurance of Different Vegetables. The degree of cold 

 which plants will survive depends upon several considerations and 

 conditions, involving state of air, moisture and of the plant itself, 

 which makes it impossible to fix the injury point of a plant definitely. 

 There is, however, practical value in the following compilation 

 made from reports by Pacific Coast growers as to the effect of our 

 style of low temperatures, the temperatures being given as nearly 

 as possible those in contact with the plant itself : 



TEMPERATURE AT WHICH CERTAIN PLANTS ARE LIABLE TO RECEIVE 

 INJURY FROM FROSTS. 



Plant Degrees Fahrenheit Plant Degrees Fahrenheit 



Asparagus 29 Beans 31 



Cantaloupes 32 Celery 28 



Cucumbers 32 Onions 28 



Potatoes 30 Sweet Potatoes 31 



Spinach 21 Squash 31 



Turnips 26 Watermelons 31 



Not Always Freezing at 32 Degrees. In connection with the 

 endurance of vegetables, it should be noted that in parts of Cali- 

 fornia freezing effects are not produced by a temperature of 32 

 degrees. This is in accordance with a deduction from wide studies 

 of frost occurrence by P. C. Day, Chief of Climatological Division of 

 the U. S. Weather Bureau, as follows : "Cool nights are a feature 

 of all arid regions, due to intense radiation made possible by the 

 generally clear skies and lack of moisture in the atmosphere. As a 

 result of these conditions the temperature in the early morning 



