VEGETABLES AND FROST 103 



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 pos- 

 sible 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 



Cantaloups 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 fea- 

 ture 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 

 hours may frequently reach the freezing point, but its continuance 

 may not be for a length of time sufficient to injure the plant struc- 

 ture ; in fact, owing to the dryness of the air, frost does not always 

 form with a temperature of 32 degrees or even several degrees 

 lower, and in addition plant life subjected to such variations in tem- 

 perature becomes more hardy and lower temperatures are required 

 to cause serious injury. On the other hand, in the more humid 

 regions the radiation at night is less rapid, the nights as a rule are 

 not so markedly cold, plant life is less hardy, frost forms readily 

 at the freezing point, the same degree of cold is often protracted 

 over much longer periods of time, and vegetation is, therefore, 

 more seriously affected/'* 



SUCCESSIONS AND ROTATIONS IN CALIFORNIA GARDENS. 



Naturally, an all-the-year growing season suggests constant use 

 of the ground and the possibility of turning the soil over several 

 times in the course of the year. This can be done by quick revolu- 

 tion, like the following: 



Where water is handy two, three, or even four crops can be grown on the 

 same ground in the year. Start April 1 and sow the plot to lettuce, and with 



*Frost data of the United States Bulletin V, U. S. Weather Bureau, 1911. 



