148 CALIFORNIA VEGETABLES. 



tions are everywhere dependent to a degree on local to- 

 pography and environment, even though there are regional 

 characters which must be understood. In this place it is 

 fitting to emphasize especially the dates at which killing 

 frosts have occurred in a large number of localities, be- 

 cause such dates are seldom accurately remembered even 

 in the localities concerned. The table which we have com- 

 piled and arranged in our own way, according to districts, 

 from data kindly furnished by Prof. McAdie, should be 

 studied with the following points in view : 



First. The dates represent the first and last dates of 

 killing frosts in each place during a decade. In most 

 cases probably the dates are not in the same year. We 

 wish to show the "worst ever" at each place. 



Second. Obviously, then, frosts at such dates are not 

 to be often expected, and planters may usually take the 

 risk of planting somewhat earlier and having tender plants 

 mature somewhat later, as will be discussed in the next 

 chapter. At the same time large plantings for a main or 

 standard crop should be generally held back for the local 

 frost-free period which the dates in the tables supply for 

 each place. 



Third. Always remember, however, that there may be 

 situations adjacent to the place where the record is made 

 in which frost may be earlier or later, or both, according 

 to the variations in local topography, exposure, etc., as 

 explained in the chapter on Climate. There are also a 

 few widely separated situations which may be considered 

 almost, if not quite, frostless. 



Fourth. The tables give the elevation in feet above sea 

 level in each case. This factor does influence frost occur- 

 rence in a large way, but local frost phenomena are often 

 determined by the relative elevation of situations in the 

 same vicinity and by other conditions of topography 

 affecting the movement of cold air and counter currents, 

 perhaps, of warm air. 



Fifth. Thus it should appear that after all the writer 

 can do to help the reader determine what his planting 



